sources for the literature review

Literature review sources

Sources for literature review can be divided into three categories as illustrated in table below. In your dissertation you will need to use all three categories of literature review sources:

Sources for literature review and examples

Generally, your literature review should integrate a wide range of sources such as:

• Books . Textbooks remain as the most important source to find models and theories related to the research area. Research the most respected authorities in your selected research area and find the latest editions of books authored by them. For example, in the area of marketing the most notable authors include Philip Kotler, Seth Godin, Malcolm Gladwell, Emanuel Rosen and others.
• Magazines . Industry-specific magazines are usually rich in scholarly articles and they can be effective source to learn about the latest trends and developments in the research area. Reading industry magazines can be the most enjoyable part of the literature review, assuming that your selected research area represents an area of your personal and professional interests, which should be the case anyways.
• Newspapers can be referred to as the main source of up-to-date news about the latest events related to the research area. However, the proportion of the use of newspapers in literature review is recommended to be less compared to alternative sources of secondary data such as books and magazines. This is due to the fact that newspaper articles mainly lack depth of analyses and discussions.
• Online articles . You can find online versions of all of the above sources. However, note that the levels of reliability of online articles can be highly compromised depending on the source due to the high levels of ease with which articles can be published online. Opinions offered in a wide range of online discussion blogs cannot be usually used in literature review. Similarly, dissertation assessors are not keen to appreciate references to a wide range of blogs, unless articles in these blogs are authored by respected authorities in the research area.

Your secondary data sources may comprise certain amount of grey literature as well. The term grey literature refers to type of literature produced by government, academics, business and industry in print and electronic formats, which is not controlled by commercial publishers. It is called ‘grey’ because the status of the information in grey literature is not certain. In other words, any publication that has not been peer reviewed for publication is grey literature.

The necessity to use grey literature arises when there is no enough peer reviewed publications are available for the subject of your study.

John Dudovskiy

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A literature review surveys prior research published in books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated. Literature reviews are designed to provide an overview of sources you have used in researching a particular topic and to demonstrate to your readers how your research fits within existing scholarship about the topic.

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . Fourth edition. Thousand Oaks, CA: SAGE, 2014.

Importance of a Good Literature Review

A literature review may consist of simply a summary of key sources, but in the social sciences, a literature review usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories . A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that informs how you are planning to investigate a research problem. The analytical features of a literature review might:

• Give a new interpretation of old material or combine new with old interpretations,
• Trace the intellectual progression of the field, including major debates,
• Depending on the situation, evaluate the sources and advise the reader on the most pertinent or relevant research, or
• Usually in the conclusion of a literature review, identify where gaps exist in how a problem has been researched to date.

Given this, the purpose of a literature review is to:

• Place each work in the context of its contribution to understanding the research problem being studied.
• Describe the relationship of each work to the others under consideration.
• Identify new ways to interpret prior research.
• Reveal any gaps that exist in the literature.
• Resolve conflicts amongst seemingly contradictory previous studies.
• Identify areas of prior scholarship to prevent duplication of effort.
• Point the way in fulfilling a need for additional research.
• Locate your own research within the context of existing literature [very important].

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper. 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . Los Angeles, CA: SAGE, 2011; Knopf, Jeffrey W. "Doing a Literature Review." PS: Political Science and Politics 39 (January 2006): 127-132; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012.

Types of Literature Reviews

It is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the primary studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally among scholars that become part of the body of epistemological traditions within the field.

In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews. Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are a number of approaches you could adopt depending upon the type of analysis underpinning your study.

Argumentative Review This form examines literature selectively in order to support or refute an argument, deeply embedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to make summary claims of the sort found in systematic reviews [see below].

Integrative Review Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses or research problems. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication. This is the most common form of review in the social sciences.

Historical Review Few things rest in isolation from historical precedent. Historical literature reviews focus on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review A review does not always focus on what someone said [findings], but how they came about saying what they say [method of analysis]. Reviewing methods of analysis provides a framework of understanding at different levels [i.e. those of theory, substantive fields, research approaches, and data collection and analysis techniques], how researchers draw upon a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection, and data analysis. This approach helps highlight ethical issues which you should be aware of and consider as you go through your own study.

Systematic Review This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyze data from the studies that are included in the review. The goal is to deliberately document, critically evaluate, and summarize scientifically all of the research about a clearly defined research problem . Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?" This type of literature review is primarily applied to examining prior research studies in clinical medicine and allied health fields, but it is increasingly being used in the social sciences.

Theoretical Review The purpose of this form is to examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review helps to establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

NOTE: Most often the literature review will incorporate some combination of types. For example, a review that examines literature supporting or refuting an argument, assumption, or philosophical problem related to the research problem will also need to include writing supported by sources that establish the history of these arguments in the literature.

Baumeister, Roy F. and Mark R. Leary. "Writing Narrative Literature Reviews."  Review of General Psychology 1 (September 1997): 311-320; Mark R. Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Kennedy, Mary M. "Defining a Literature." Educational Researcher 36 (April 2007): 139-147; Petticrew, Mark and Helen Roberts. Systematic Reviews in the Social Sciences: A Practical Guide . Malden, MA: Blackwell Publishers, 2006; Torracro, Richard. "Writing Integrative Literature Reviews: Guidelines and Examples." Human Resource Development Review 4 (September 2005): 356-367; Rocco, Tonette S. and Maria S. Plakhotnik. "Literature Reviews, Conceptual Frameworks, and Theoretical Frameworks: Terms, Functions, and Distinctions." Human Ressource Development Review 8 (March 2008): 120-130; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

Structure and Writing Style

I.  Thinking About Your Literature Review

The structure of a literature review should include the following in support of understanding the research problem :

• An overview of the subject, issue, or theory under consideration, along with the objectives of the literature review,
• Division of works under review into themes or categories [e.g. works that support a particular position, those against, and those offering alternative approaches entirely],
• An explanation of how each work is similar to and how it varies from the others,
• Conclusions as to which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of their area of research.

The critical evaluation of each work should consider :

• Provenance -- what are the author's credentials? Are the author's arguments supported by evidence [e.g. primary historical material, case studies, narratives, statistics, recent scientific findings]?
• Methodology -- were the techniques used to identify, gather, and analyze the data appropriate to addressing the research problem? Was the sample size appropriate? Were the results effectively interpreted and reported?
• Objectivity -- is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
• Persuasiveness -- which of the author's theses are most convincing or least convincing?
• Validity -- are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

II.  Development of the Literature Review

Four Basic Stages of Writing 1.  Problem formulation -- which topic or field is being examined and what are its component issues? 2.  Literature search -- finding materials relevant to the subject being explored. 3.  Data evaluation -- determining which literature makes a significant contribution to the understanding of the topic. 4.  Analysis and interpretation -- discussing the findings and conclusions of pertinent literature.

Consider the following issues before writing the literature review: Clarify If your assignment is not specific about what form your literature review should take, seek clarification from your professor by asking these questions: 1.  Roughly how many sources would be appropriate to include? 2.  What types of sources should I review (books, journal articles, websites; scholarly versus popular sources)? 3.  Should I summarize, synthesize, or critique sources by discussing a common theme or issue? 4.  Should I evaluate the sources in any way beyond evaluating how they relate to understanding the research problem? 5.  Should I provide subheadings and other background information, such as definitions and/or a history? Find Models Use the exercise of reviewing the literature to examine how authors in your discipline or area of interest have composed their literature review sections. Read them to get a sense of the types of themes you might want to look for in your own research or to identify ways to organize your final review. The bibliography or reference section of sources you've already read, such as required readings in the course syllabus, are also excellent entry points into your own research. Narrow the Topic The narrower your topic, the easier it will be to limit the number of sources you need to read in order to obtain a good survey of relevant resources. Your professor will probably not expect you to read everything that's available about the topic, but you'll make the act of reviewing easier if you first limit scope of the research problem. A good strategy is to begin by searching the USC Libraries Catalog for recent books about the topic and review the table of contents for chapters that focuses on specific issues. You can also review the indexes of books to find references to specific issues that can serve as the focus of your research. For example, a book surveying the history of the Israeli-Palestinian conflict may include a chapter on the role Egypt has played in mediating the conflict, or look in the index for the pages where Egypt is mentioned in the text. Consider Whether Your Sources are Current Some disciplines require that you use information that is as current as possible. This is particularly true in disciplines in medicine and the sciences where research conducted becomes obsolete very quickly as new discoveries are made. However, when writing a review in the social sciences, a survey of the history of the literature may be required. In other words, a complete understanding the research problem requires you to deliberately examine how knowledge and perspectives have changed over time. Sort through other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to explore what is considered by scholars to be a "hot topic" and what is not.

III.  Ways to Organize Your Literature Review

Chronology of Events If your review follows the chronological method, you could write about the materials according to when they were published. This approach should only be followed if a clear path of research building on previous research can be identified and that these trends follow a clear chronological order of development. For example, a literature review that focuses on continuing research about the emergence of German economic power after the fall of the Soviet Union. By Publication Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on environmental studies of brown fields if the progression revealed, for example, a change in the soil collection practices of the researchers who wrote and/or conducted the studies. Thematic [“conceptual categories”] A thematic literature review is the most common approach to summarizing prior research in the social and behavioral sciences. Thematic reviews are organized around a topic or issue, rather than the progression of time, although the progression of time may still be incorporated into a thematic review. For example, a review of the Internet’s impact on American presidential politics could focus on the development of online political satire. While the study focuses on one topic, the Internet’s impact on American presidential politics, it would still be organized chronologically reflecting technological developments in media. The difference in this example between a "chronological" and a "thematic" approach is what is emphasized the most: themes related to the role of the Internet in presidential politics. Note that more authentic thematic reviews tend to break away from chronological order. A review organized in this manner would shift between time periods within each section according to the point being made. Methodological A methodological approach focuses on the methods utilized by the researcher. For the Internet in American presidential politics project, one methodological approach would be to look at cultural differences between the portrayal of American presidents on American, British, and French websites. Or the review might focus on the fundraising impact of the Internet on a particular political party. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed.

Other Sections of Your Literature Review Once you've decided on the organizational method for your literature review, the sections you need to include in the paper should be easy to figure out because they arise from your organizational strategy. In other words, a chronological review would have subsections for each vital time period; a thematic review would have subtopics based upon factors that relate to the theme or issue. However, sometimes you may need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. However, only include what is necessary for the reader to locate your study within the larger scholarship about the research problem.

Here are examples of other sections, usually in the form of a single paragraph, you may need to include depending on the type of review you write:

• Current Situation : Information necessary to understand the current topic or focus of the literature review.
• Sources Used : Describes the methods and resources [e.g., databases] you used to identify the literature you reviewed.
• History : The chronological progression of the field, the research literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
• Selection Methods : Criteria you used to select (and perhaps exclude) sources in your literature review. For instance, you might explain that your review includes only peer-reviewed [i.e., scholarly] sources.
• Standards : Description of the way in which you present your information.
• Questions for Further Research : What questions about the field has the review sparked? How will you further your research as a result of the review?

IV.  Writing Your Literature Review

Once you've settled on how to organize your literature review, you're ready to write each section. When writing your review, keep in mind these issues.

Use Evidence A literature review section is, in this sense, just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence [citations] that demonstrates that what you are saying is valid. Be Selective Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the research problem, whether it is thematic, methodological, or chronological. Related items that provide additional information, but that are not key to understanding the research problem, can be included in a list of further readings . Use Quotes Sparingly Some short quotes are appropriate if you want to emphasize a point, or if what an author stated cannot be easily paraphrased. Sometimes you may need to quote certain terminology that was coined by the author, is not common knowledge, or taken directly from the study. Do not use extensive quotes as a substitute for using your own words in reviewing the literature. Summarize and Synthesize Remember to summarize and synthesize your sources within each thematic paragraph as well as throughout the review. Recapitulate important features of a research study, but then synthesize it by rephrasing the study's significance and relating it to your own work and the work of others. Keep Your Own Voice While the literature review presents others' ideas, your voice [the writer's] should remain front and center. For example, weave references to other sources into what you are writing but maintain your own voice by starting and ending the paragraph with your own ideas and wording. Use Caution When Paraphrasing When paraphrasing a source that is not your own, be sure to represent the author's information or opinions accurately and in your own words. Even when paraphrasing an author’s work, you still must provide a citation to that work.

V.  Common Mistakes to Avoid

These are the most common mistakes made in reviewing social science research literature.

• Sources in your literature review do not clearly relate to the research problem;
• You do not take sufficient time to define and identify the most relevant sources to use in the literature review related to the research problem;
• Relies exclusively on secondary analytical sources rather than including relevant primary research studies or data;
• Uncritically accepts another researcher's findings and interpretations as valid, rather than examining critically all aspects of the research design and analysis;
• Does not describe the search procedures that were used in identifying the literature to review;
• Reports isolated statistical results rather than synthesizing them in chi-squared or meta-analytic methods; and,
• Only includes research that validates assumptions and does not consider contrary findings and alternative interpretations found in the literature.

Cook, Kathleen E. and Elise Murowchick. “Do Literature Review Skills Transfer from One Course to Another?” Psychology Learning and Teaching 13 (March 2014): 3-11; Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . London: SAGE, 2011; Literature Review Handout. Online Writing Center. Liberty University; Literature Reviews. The Writing Center. University of North Carolina; Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: SAGE, 2016; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012; Randolph, Justus J. “A Guide to Writing the Dissertation Literature Review." Practical Assessment, Research, and Evaluation. vol. 14, June 2009; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016; Taylor, Dena. The Literature Review: A Few Tips On Conducting It. University College Writing Centre. University of Toronto; Writing a Literature Review. Academic Skills Centre. University of Canberra.

Writing Tip

Break Out of Your Disciplinary Box!

Thinking interdisciplinarily about a research problem can be a rewarding exercise in applying new ideas, theories, or concepts to an old problem. For example, what might cultural anthropologists say about the continuing conflict in the Middle East? In what ways might geographers view the need for better distribution of social service agencies in large cities than how social workers might study the issue? You don’t want to substitute a thorough review of core research literature in your discipline for studies conducted in other fields of study. However, particularly in the social sciences, thinking about research problems from multiple vectors is a key strategy for finding new solutions to a problem or gaining a new perspective. Consult with a librarian about identifying research databases in other disciplines; almost every field of study has at least one comprehensive database devoted to indexing its research literature.

Frodeman, Robert. The Oxford Handbook of Interdisciplinarity . New York: Oxford University Press, 2010.

Another Writing Tip

Don't Just Review for Content!

While conducting a review of the literature, maximize the time you devote to writing this part of your paper by thinking broadly about what you should be looking for and evaluating. Review not just what scholars are saying, but how are they saying it. Some questions to ask:

• How are they organizing their ideas?
• What methods have they used to study the problem?
• What theories have been used to explain, predict, or understand their research problem?
• What sources have they cited to support their conclusions?
• How have they used non-textual elements [e.g., charts, graphs, figures, etc.] to illustrate key points?

When you begin to write your literature review section, you'll be glad you dug deeper into how the research was designed and constructed because it establishes a means for developing more substantial analysis and interpretation of the research problem.

Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1 998.

Yet Another Writing Tip

When Do I Know I Can Stop Looking and Move On?

Here are several strategies you can utilize to assess whether you've thoroughly reviewed the literature:

• Look for repeating patterns in the research findings . If the same thing is being said, just by different people, then this likely demonstrates that the research problem has hit a conceptual dead end. At this point consider: Does your study extend current research?  Does it forge a new path? Or, does is merely add more of the same thing being said?
• Look at sources the authors cite to in their work . If you begin to see the same researchers cited again and again, then this is often an indication that no new ideas have been generated to address the research problem.
• Search Google Scholar to identify who has subsequently cited leading scholars already identified in your literature review [see next sub-tab]. This is called citation tracking and there are a number of sources that can help you identify who has cited whom, particularly scholars from outside of your discipline. Here again, if the same authors are being cited again and again, this may indicate no new literature has been written on the topic.

Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: Sage, 2016; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

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Researching for your literature review: Literature sources

• Literature reviews
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Scholarly databases

It's important to make a considered decision as to where to search for your review of the literature. It's uncommon for a disciplinary area to be covered by a single publisher, so searching a single publisher platform or database is unlikely to give you sufficient coverage of studies for a review. A good quality literature review involves searching a number of databases individually.

The most common method is to search a combination of large inter-disciplinary databases such as Scopus & Web of Science Core Collection, and some subject-specific databases (such as PsycInfo or EconLit etc.). The Library databases are an excellent place to start for sources of peer-reviewed journal articles.

Depending on disciplinary expectations, or the topic of our review, you may also need to consider sources or search methods other than database searching. There is general information below on searching grey literature. However, due to the wide varieties of grey literature available, you may need to spend some time investigating sources relevant for your specific need.

Grey literature

Grey literature is information which has been published informally or non-commercially (where the main purpose of the producing body is not commercial publishing) or remains unpublished. One example may be Government publications.

Grey literature may be included in a literature review to minimise publication bias . The quality of grey literature can vary greatly - some may be peer reviewed whereas some may not have been through a traditional editorial process.

See the Grey Literature guide for further information on finding and evaluating grey sources.

See the Moodle book MNHS: Systematically searching the grey literature for a comprehensive module on grey literature for systematic reviews.

In certain disciplines (such as physics) there can be a culture of preprints being made available prior to submissions to journals. There has also been a noticeable rise in preprints in medical and health areas in the wake of Covid-19.

If preprints are relevant for you, you can search preprint servers directly. A workaround might be to utilise a search engine such as Google Scholar to search specifically for preprints, as Google Scholar has timely coverage of most preprint servers including ArXiv, RePec, SSRN, BioRxiv, and MedRxiv.

Articles in Press are not preprints, but are accepted manuscripts that are not yet formally published. Articles in Press have been made available as an early access online version of a paper that may not yet have received its final formatting or an allocation of a volume/issue number. As well as being available on a journal's website, Articles in Press are available in databases such as Scopus and Web of Science, and so (unlike preprints) don't necessarily require a separate search.

Conference papers

Conference papers are typically published in conference proceedings (the collection of papers presented at a conference), and may be found on an organisation or Society's website, as a journal, or as a special issue of journal.

In certain disciplines (such as computer science), conference papers may be highly regarded as a form of scholarly communication; the conferences are highly selective, the papers are generally peer reviewed, and papers are published in proceedings affiliated with high-quality publishing houses.

Conference papers may be indexed in a range of scholarly databases. If you only want to see conference papers, database limits can be used to filter results, or try a specific index such as the examples below:

• Conference proceedings citation index. Social science & humanities (CPCI-SSH)
• Conference proceedings citation index. Science (CPCI-S)
• ASME digital library conference proceedings

Honours students and postgraduates may request conference papers through Interlibrary Loans . However, conference paper requests may take longer than traditional article requests as they can be difficult to locate; they may have been only supplied to attendees or not formally published. Sometimes only the abstract is available.

If you are specifically looking for statistical data, try searching for the keyword statistics in a Google Advanced Search and limiting by a relevant site or domain. Below are some examples of sites, or you can try a domain such as .gov for government websites.

Statistical data can be found in the following selected sources:

• Australian Bureau of Statistics
• World Health Organization: Health Data and statistics
• Higher Education Statistics
• UNESCO Institute for Statistics
• Tourism Australia Statistics

For a list of databases that include statistics see: Databases by Subject: Statistics .

If you are specifically looking for information found in newspapers, the library has a large collection of Australian and overseas newspapers, both current and historical.

To search the full-text of newspapers in electronic format use a database such as  Newsbank.

Alternatively, see the Newspapers subject guide for comprehensive information on newspaper sources available via Monash University library and open source databases, as well as searching tips, online videos and more.

Dissertations and theses

The Monash University Library Theses subject guide provides resources and guidelines for locating and accessing theses (dissertations) produced by Monash University as well as other universities in Australia and internationally.  

International theses:

There are a number of theses databases and repositories.

A popular source is:

• ProQuest Dissertations & Theses Global  which predominantly, covers North American masters and doctoral theses. Full text is available for theses added since 1997. 

Australia and New Zealand theses:

Theses that are available in the library can be found using the  Search catalogue.

These include:

• Monash doctoral, masters and a small number of honours theses 
• other Australian and overseas theses that have been purchased for the collection.

Formats include print (not available for loan), microfiche and online (some may have access restrictions).

Trove includes doctoral, masters and some honours theses from all Australian and New Zealand universities, as well as theses awarded elsewhere but held by Australian institutions.

Tips:  

• Type in the title, author surname and/or keywords. Then on the results page refine your search to 'thesis'.
• Alternatively, use the Advanced search and include 'thesis' as a keyword or limi t your result to format = thesis
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• Steps in Conducting a Literature Review

What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Discovers relationships between research studies/ideas.
• Identifies major themes, concepts, and researchers on a topic.
• Identifies critical gaps and points of disagreement.
• Discusses further research questions that logically come out of the previous studies.

APA7 Style resources

APA Style Blog - for those harder to find answers

1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

• Make sure your research question is not too broad or too narrow.  Is it manageable?
• Begin writing down terms that are related to your question. These will be useful for searches later.
• If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

• This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

• use the tabs on this guide
• Find other databases in the Nursing Information Resources web page
• More on the Medical Library web page
• ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

• Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
• Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
• Review the abstracts of research studies carefully. This will save you time.
• Use the bibliographies and references of research studies you find to locate others.
• Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
• Ask your librarian for help at any time.
• Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

• What was the research question of the study you are reviewing? What were the authors trying to discover?
• Was the research funded by a source that could influence the findings?
• What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
• Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
• If there are conflicting studies, why do you think that is?
• How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

• Review the abstracts carefully.  
• Keep careful notes so that you may track your thought processes during the research process.
• Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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• What is a Literature Review? | Guide, Template, & Examples

What is a Literature Review? | Guide, Template, & Examples

Published on 22 February 2022 by Shona McCombes . Revised on 7 June 2022.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research.

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarise sources – it analyses, synthesises, and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

Why write a literature review, examples of literature reviews, step 1: search for relevant literature, step 2: evaluate and select sources, step 3: identify themes, debates and gaps, step 4: outline your literature review’s structure, step 5: write your literature review, frequently asked questions about literature reviews, introduction.

• Quick Run-through
• Step 1 & 2

When you write a dissertation or thesis, you will have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and scholarly context
• Develop a theoretical framework and methodology for your research
• Position yourself in relation to other researchers and theorists
• Show how your dissertation addresses a gap or contributes to a debate

You might also have to write a literature review as a stand-alone assignment. In this case, the purpose is to evaluate the current state of research and demonstrate your knowledge of scholarly debates around a topic.

The content will look slightly different in each case, but the process of conducting a literature review follows the same steps. We’ve written a step-by-step guide that you can follow below.

Prevent plagiarism, run a free check.

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research objectives and questions .

If you are writing a literature review as a stand-alone assignment, you will have to choose a focus and develop a central question to direct your search. Unlike a dissertation research question, this question has to be answerable without collecting original data. You should be able to answer it based only on a review of existing publications.

Make a list of keywords

Start by creating a list of keywords related to your research topic. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list if you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can use boolean operators to help narrow down your search:

Read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

To identify the most important publications on your topic, take note of recurring citations. If the same authors, books or articles keep appearing in your reading, make sure to seek them out.

You probably won’t be able to read absolutely everything that has been written on the topic – you’ll have to evaluate which sources are most relevant to your questions.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models and methods? Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• How does the publication contribute to your understanding of the topic? What are its key insights and arguments?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible, and make sure you read any landmark studies and major theories in your field of research.

You can find out how many times an article has been cited on Google Scholar – a high citation count means the article has been influential in the field, and should certainly be included in your literature review.

The scope of your review will depend on your topic and discipline: in the sciences you usually only review recent literature, but in the humanities you might take a long historical perspective (for example, to trace how a concept has changed in meaning over time).

Remember that you can use our template to summarise and evaluate sources you’re thinking about using!

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It’s important to keep track of your sources with references to avoid plagiarism . It can be helpful to make an annotated bibliography, where you compile full reference information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

You can use our free APA Reference Generator for quick, correct, consistent citations.

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To begin organising your literature review’s argument and structure, you need to understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly-visual platforms like Instagram and Snapchat – this is a gap that you could address in your own research.

There are various approaches to organising the body of a literature review. You should have a rough idea of your strategy before you start writing.

Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarising sources in order.

Try to analyse patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organise your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text, your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

If you are writing the literature review as part of your dissertation or thesis, reiterate your central problem or research question and give a brief summary of the scholarly context. You can emphasise the timeliness of the topic (“many recent studies have focused on the problem of x”) or highlight a gap in the literature (“while there has been much research on x, few researchers have taken y into consideration”).

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, make sure to follow these tips:

• Summarise and synthesise: give an overview of the main points of each source and combine them into a coherent whole.
• Analyse and interpret: don’t just paraphrase other researchers – add your own interpretations, discussing the significance of findings in relation to the literature as a whole.
• Critically evaluate: mention the strengths and weaknesses of your sources.
• Write in well-structured paragraphs: use transitions and topic sentences to draw connections, comparisons and contrasts.

In the conclusion, you should summarise the key findings you have taken from the literature and emphasise their significance.

If the literature review is part of your dissertation or thesis, reiterate how your research addresses gaps and contributes new knowledge, or discuss how you have drawn on existing theories and methods to build a framework for your research. This can lead directly into your methodology section.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a dissertation , thesis, research paper , or proposal .

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarise yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your  dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

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Ten Simple Rules for Writing a Literature Review

Marco pautasso.

1 Centre for Functional and Evolutionary Ecology (CEFE), CNRS, Montpellier, France

2 Centre for Biodiversity Synthesis and Analysis (CESAB), FRB, Aix-en-Provence, France

Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications [1] . For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively [2] . Given such mountains of papers, scientists cannot be expected to examine in detail every single new paper relevant to their interests [3] . Thus, it is both advantageous and necessary to rely on regular summaries of the recent literature. Although recognition for scientists mainly comes from primary research, timely literature reviews can lead to new synthetic insights and are often widely read [4] . For such summaries to be useful, however, they need to be compiled in a professional way [5] .

When starting from scratch, reviewing the literature can require a titanic amount of work. That is why researchers who have spent their career working on a certain research issue are in a perfect position to review that literature. Some graduate schools are now offering courses in reviewing the literature, given that most research students start their project by producing an overview of what has already been done on their research issue [6] . However, it is likely that most scientists have not thought in detail about how to approach and carry out a literature review.

Reviewing the literature requires the ability to juggle multiple tasks, from finding and evaluating relevant material to synthesising information from various sources, from critical thinking to paraphrasing, evaluating, and citation skills [7] . In this contribution, I share ten simple rules I learned working on about 25 literature reviews as a PhD and postdoctoral student. Ideas and insights also come from discussions with coauthors and colleagues, as well as feedback from reviewers and editors.

Rule 1: Define a Topic and Audience

How to choose which topic to review? There are so many issues in contemporary science that you could spend a lifetime of attending conferences and reading the literature just pondering what to review. On the one hand, if you take several years to choose, several other people may have had the same idea in the meantime. On the other hand, only a well-considered topic is likely to lead to a brilliant literature review [8] . The topic must at least be:

• interesting to you (ideally, you should have come across a series of recent papers related to your line of work that call for a critical summary),
• an important aspect of the field (so that many readers will be interested in the review and there will be enough material to write it), and
• a well-defined issue (otherwise you could potentially include thousands of publications, which would make the review unhelpful).

Ideas for potential reviews may come from papers providing lists of key research questions to be answered [9] , but also from serendipitous moments during desultory reading and discussions. In addition to choosing your topic, you should also select a target audience. In many cases, the topic (e.g., web services in computational biology) will automatically define an audience (e.g., computational biologists), but that same topic may also be of interest to neighbouring fields (e.g., computer science, biology, etc.).

Rule 2: Search and Re-search the Literature

After having chosen your topic and audience, start by checking the literature and downloading relevant papers. Five pieces of advice here:

• keep track of the search items you use (so that your search can be replicated [10] ),
• keep a list of papers whose pdfs you cannot access immediately (so as to retrieve them later with alternative strategies),
• use a paper management system (e.g., Mendeley, Papers, Qiqqa, Sente),
• define early in the process some criteria for exclusion of irrelevant papers (these criteria can then be described in the review to help define its scope), and
• do not just look for research papers in the area you wish to review, but also seek previous reviews.

The chances are high that someone will already have published a literature review ( Figure 1 ), if not exactly on the issue you are planning to tackle, at least on a related topic. If there are already a few or several reviews of the literature on your issue, my advice is not to give up, but to carry on with your own literature review,

The bottom-right situation (many literature reviews but few research papers) is not just a theoretical situation; it applies, for example, to the study of the impacts of climate change on plant diseases, where there appear to be more literature reviews than research studies [33] .

• discussing in your review the approaches, limitations, and conclusions of past reviews,
• trying to find a new angle that has not been covered adequately in the previous reviews, and
• incorporating new material that has inevitably accumulated since their appearance.

When searching the literature for pertinent papers and reviews, the usual rules apply:

• be thorough,
• use different keywords and database sources (e.g., DBLP, Google Scholar, ISI Proceedings, JSTOR Search, Medline, Scopus, Web of Science), and
• look at who has cited past relevant papers and book chapters.

Rule 3: Take Notes While Reading

If you read the papers first, and only afterwards start writing the review, you will need a very good memory to remember who wrote what, and what your impressions and associations were while reading each single paper. My advice is, while reading, to start writing down interesting pieces of information, insights about how to organize the review, and thoughts on what to write. This way, by the time you have read the literature you selected, you will already have a rough draft of the review.

Of course, this draft will still need much rewriting, restructuring, and rethinking to obtain a text with a coherent argument [11] , but you will have avoided the danger posed by staring at a blank document. Be careful when taking notes to use quotation marks if you are provisionally copying verbatim from the literature. It is advisable then to reformulate such quotes with your own words in the final draft. It is important to be careful in noting the references already at this stage, so as to avoid misattributions. Using referencing software from the very beginning of your endeavour will save you time.

Rule 4: Choose the Type of Review You Wish to Write

After having taken notes while reading the literature, you will have a rough idea of the amount of material available for the review. This is probably a good time to decide whether to go for a mini- or a full review. Some journals are now favouring the publication of rather short reviews focusing on the last few years, with a limit on the number of words and citations. A mini-review is not necessarily a minor review: it may well attract more attention from busy readers, although it will inevitably simplify some issues and leave out some relevant material due to space limitations. A full review will have the advantage of more freedom to cover in detail the complexities of a particular scientific development, but may then be left in the pile of the very important papers “to be read” by readers with little time to spare for major monographs.

There is probably a continuum between mini- and full reviews. The same point applies to the dichotomy of descriptive vs. integrative reviews. While descriptive reviews focus on the methodology, findings, and interpretation of each reviewed study, integrative reviews attempt to find common ideas and concepts from the reviewed material [12] . A similar distinction exists between narrative and systematic reviews: while narrative reviews are qualitative, systematic reviews attempt to test a hypothesis based on the published evidence, which is gathered using a predefined protocol to reduce bias [13] , [14] . When systematic reviews analyse quantitative results in a quantitative way, they become meta-analyses. The choice between different review types will have to be made on a case-by-case basis, depending not just on the nature of the material found and the preferences of the target journal(s), but also on the time available to write the review and the number of coauthors [15] .

Rule 5: Keep the Review Focused, but Make It of Broad Interest

Whether your plan is to write a mini- or a full review, it is good advice to keep it focused 16 , 17 . Including material just for the sake of it can easily lead to reviews that are trying to do too many things at once. The need to keep a review focused can be problematic for interdisciplinary reviews, where the aim is to bridge the gap between fields [18] . If you are writing a review on, for example, how epidemiological approaches are used in modelling the spread of ideas, you may be inclined to include material from both parent fields, epidemiology and the study of cultural diffusion. This may be necessary to some extent, but in this case a focused review would only deal in detail with those studies at the interface between epidemiology and the spread of ideas.

While focus is an important feature of a successful review, this requirement has to be balanced with the need to make the review relevant to a broad audience. This square may be circled by discussing the wider implications of the reviewed topic for other disciplines.

Rule 6: Be Critical and Consistent

Reviewing the literature is not stamp collecting. A good review does not just summarize the literature, but discusses it critically, identifies methodological problems, and points out research gaps [19] . After having read a review of the literature, a reader should have a rough idea of:

• the major achievements in the reviewed field,
• the main areas of debate, and
• the outstanding research questions.

It is challenging to achieve a successful review on all these fronts. A solution can be to involve a set of complementary coauthors: some people are excellent at mapping what has been achieved, some others are very good at identifying dark clouds on the horizon, and some have instead a knack at predicting where solutions are going to come from. If your journal club has exactly this sort of team, then you should definitely write a review of the literature! In addition to critical thinking, a literature review needs consistency, for example in the choice of passive vs. active voice and present vs. past tense.

Rule 7: Find a Logical Structure

Like a well-baked cake, a good review has a number of telling features: it is worth the reader's time, timely, systematic, well written, focused, and critical. It also needs a good structure. With reviews, the usual subdivision of research papers into introduction, methods, results, and discussion does not work or is rarely used. However, a general introduction of the context and, toward the end, a recapitulation of the main points covered and take-home messages make sense also in the case of reviews. For systematic reviews, there is a trend towards including information about how the literature was searched (database, keywords, time limits) [20] .

How can you organize the flow of the main body of the review so that the reader will be drawn into and guided through it? It is generally helpful to draw a conceptual scheme of the review, e.g., with mind-mapping techniques. Such diagrams can help recognize a logical way to order and link the various sections of a review [21] . This is the case not just at the writing stage, but also for readers if the diagram is included in the review as a figure. A careful selection of diagrams and figures relevant to the reviewed topic can be very helpful to structure the text too [22] .

Rule 8: Make Use of Feedback

Reviews of the literature are normally peer-reviewed in the same way as research papers, and rightly so [23] . As a rule, incorporating feedback from reviewers greatly helps improve a review draft. Having read the review with a fresh mind, reviewers may spot inaccuracies, inconsistencies, and ambiguities that had not been noticed by the writers due to rereading the typescript too many times. It is however advisable to reread the draft one more time before submission, as a last-minute correction of typos, leaps, and muddled sentences may enable the reviewers to focus on providing advice on the content rather than the form.

Feedback is vital to writing a good review, and should be sought from a variety of colleagues, so as to obtain a diversity of views on the draft. This may lead in some cases to conflicting views on the merits of the paper, and on how to improve it, but such a situation is better than the absence of feedback. A diversity of feedback perspectives on a literature review can help identify where the consensus view stands in the landscape of the current scientific understanding of an issue [24] .

Rule 9: Include Your Own Relevant Research, but Be Objective

In many cases, reviewers of the literature will have published studies relevant to the review they are writing. This could create a conflict of interest: how can reviewers report objectively on their own work [25] ? Some scientists may be overly enthusiastic about what they have published, and thus risk giving too much importance to their own findings in the review. However, bias could also occur in the other direction: some scientists may be unduly dismissive of their own achievements, so that they will tend to downplay their contribution (if any) to a field when reviewing it.

In general, a review of the literature should neither be a public relations brochure nor an exercise in competitive self-denial. If a reviewer is up to the job of producing a well-organized and methodical review, which flows well and provides a service to the readership, then it should be possible to be objective in reviewing one's own relevant findings. In reviews written by multiple authors, this may be achieved by assigning the review of the results of a coauthor to different coauthors.

Rule 10: Be Up-to-Date, but Do Not Forget Older Studies

Given the progressive acceleration in the publication of scientific papers, today's reviews of the literature need awareness not just of the overall direction and achievements of a field of inquiry, but also of the latest studies, so as not to become out-of-date before they have been published. Ideally, a literature review should not identify as a major research gap an issue that has just been addressed in a series of papers in press (the same applies, of course, to older, overlooked studies (“sleeping beauties” [26] )). This implies that literature reviewers would do well to keep an eye on electronic lists of papers in press, given that it can take months before these appear in scientific databases. Some reviews declare that they have scanned the literature up to a certain point in time, but given that peer review can be a rather lengthy process, a full search for newly appeared literature at the revision stage may be worthwhile. Assessing the contribution of papers that have just appeared is particularly challenging, because there is little perspective with which to gauge their significance and impact on further research and society.

Inevitably, new papers on the reviewed topic (including independently written literature reviews) will appear from all quarters after the review has been published, so that there may soon be the need for an updated review. But this is the nature of science [27] – [32] . I wish everybody good luck with writing a review of the literature.

Acknowledgments

Many thanks to M. Barbosa, K. Dehnen-Schmutz, T. Döring, D. Fontaneto, M. Garbelotto, O. Holdenrieder, M. Jeger, D. Lonsdale, A. MacLeod, P. Mills, M. Moslonka-Lefebvre, G. Stancanelli, P. Weisberg, and X. Xu for insights and discussions, and to P. Bourne, T. Matoni, and D. Smith for helpful comments on a previous draft.

Funding Statement

This work was funded by the French Foundation for Research on Biodiversity (FRB) through its Centre for Synthesis and Analysis of Biodiversity data (CESAB), as part of the NETSEED research project. The funders had no role in the preparation of the manuscript.

Literature Reviews

What this handout is about.

This handout will explain what literature reviews are and offer insights into the form and construction of literature reviews in the humanities, social sciences, and sciences.

Introduction

OK. You’ve got to write a literature review. You dust off a novel and a book of poetry, settle down in your chair, and get ready to issue a “thumbs up” or “thumbs down” as you leaf through the pages. “Literature review” done. Right?

Wrong! The “literature” of a literature review refers to any collection of materials on a topic, not necessarily the great literary texts of the world. “Literature” could be anything from a set of government pamphlets on British colonial methods in Africa to scholarly articles on the treatment of a torn ACL. And a review does not necessarily mean that your reader wants you to give your personal opinion on whether or not you liked these sources.

What is a literature review, then?

A literature review discusses published information in a particular subject area, and sometimes information in a particular subject area within a certain time period.

A literature review can be just a simple summary of the sources, but it usually has an organizational pattern and combines both summary and synthesis. A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information. It might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. And depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant.

But how is a literature review different from an academic research paper?

The main focus of an academic research paper is to develop a new argument, and a research paper is likely to contain a literature review as one of its parts. In a research paper, you use the literature as a foundation and as support for a new insight that you contribute. The focus of a literature review, however, is to summarize and synthesize the arguments and ideas of others without adding new contributions.

Why do we write literature reviews?

Literature reviews provide you with a handy guide to a particular topic. If you have limited time to conduct research, literature reviews can give you an overview or act as a stepping stone. For professionals, they are useful reports that keep them up to date with what is current in the field. For scholars, the depth and breadth of the literature review emphasizes the credibility of the writer in his or her field. Literature reviews also provide a solid background for a research paper’s investigation. Comprehensive knowledge of the literature of the field is essential to most research papers.

Who writes these things, anyway?

Literature reviews are written occasionally in the humanities, but mostly in the sciences and social sciences; in experiment and lab reports, they constitute a section of the paper. Sometimes a literature review is written as a paper in itself.

Let’s get to it! What should I do before writing the literature review?

If your assignment is not very specific, seek clarification from your instructor:

• Roughly how many sources should you include?
• What types of sources (books, journal articles, websites)?
• Should you summarize, synthesize, or critique your sources by discussing a common theme or issue?
• Should you evaluate your sources?
• Should you provide subheadings and other background information, such as definitions and/or a history?

Find models

Look for other literature reviews in your area of interest or in the discipline and read them to get a sense of the types of themes you might want to look for in your own research or ways to organize your final review. You can simply put the word “review” in your search engine along with your other topic terms to find articles of this type on the Internet or in an electronic database. The bibliography or reference section of sources you’ve already read are also excellent entry points into your own research.

Narrow your topic

There are hundreds or even thousands of articles and books on most areas of study. The narrower your topic, the easier it will be to limit the number of sources you need to read in order to get a good survey of the material. Your instructor will probably not expect you to read everything that’s out there on the topic, but you’ll make your job easier if you first limit your scope.

Keep in mind that UNC Libraries have research guides and to databases relevant to many fields of study. You can reach out to the subject librarian for a consultation: https://library.unc.edu/support/consultations/ .

And don’t forget to tap into your professor’s (or other professors’) knowledge in the field. Ask your professor questions such as: “If you had to read only one book from the 90’s on topic X, what would it be?” Questions such as this help you to find and determine quickly the most seminal pieces in the field.

Consider whether your sources are current

Some disciplines require that you use information that is as current as possible. In the sciences, for instance, treatments for medical problems are constantly changing according to the latest studies. Information even two years old could be obsolete. However, if you are writing a review in the humanities, history, or social sciences, a survey of the history of the literature may be what is needed, because what is important is how perspectives have changed through the years or within a certain time period. Try sorting through some other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to consider what is currently of interest to scholars in this field and what is not.

Strategies for writing the literature review

Find a focus.

A literature review, like a term paper, is usually organized around ideas, not the sources themselves as an annotated bibliography would be organized. This means that you will not just simply list your sources and go into detail about each one of them, one at a time. No. As you read widely but selectively in your topic area, consider instead what themes or issues connect your sources together. Do they present one or different solutions? Is there an aspect of the field that is missing? How well do they present the material and do they portray it according to an appropriate theory? Do they reveal a trend in the field? A raging debate? Pick one of these themes to focus the organization of your review.

Convey it to your reader

A literature review may not have a traditional thesis statement (one that makes an argument), but you do need to tell readers what to expect. Try writing a simple statement that lets the reader know what is your main organizing principle. Here are a couple of examples:

The current trend in treatment for congestive heart failure combines surgery and medicine. More and more cultural studies scholars are accepting popular media as a subject worthy of academic consideration.

Consider organization

You’ve got a focus, and you’ve stated it clearly and directly. Now what is the most effective way of presenting the information? What are the most important topics, subtopics, etc., that your review needs to include? And in what order should you present them? Develop an organization for your review at both a global and local level:

First, cover the basic categories

Just like most academic papers, literature reviews also must contain at least three basic elements: an introduction or background information section; the body of the review containing the discussion of sources; and, finally, a conclusion and/or recommendations section to end the paper. The following provides a brief description of the content of each:

• Introduction: Gives a quick idea of the topic of the literature review, such as the central theme or organizational pattern.
• Body: Contains your discussion of sources and is organized either chronologically, thematically, or methodologically (see below for more information on each).
• Conclusions/Recommendations: Discuss what you have drawn from reviewing literature so far. Where might the discussion proceed?

Organizing the body

Once you have the basic categories in place, then you must consider how you will present the sources themselves within the body of your paper. Create an organizational method to focus this section even further.

To help you come up with an overall organizational framework for your review, consider the following scenario:

You’ve decided to focus your literature review on materials dealing with sperm whales. This is because you’ve just finished reading Moby Dick, and you wonder if that whale’s portrayal is really real. You start with some articles about the physiology of sperm whales in biology journals written in the 1980’s. But these articles refer to some British biological studies performed on whales in the early 18th century. So you check those out. Then you look up a book written in 1968 with information on how sperm whales have been portrayed in other forms of art, such as in Alaskan poetry, in French painting, or on whale bone, as the whale hunters in the late 19th century used to do. This makes you wonder about American whaling methods during the time portrayed in Moby Dick, so you find some academic articles published in the last five years on how accurately Herman Melville portrayed the whaling scene in his novel.

Now consider some typical ways of organizing the sources into a review:

• Chronological: If your review follows the chronological method, you could write about the materials above according to when they were published. For instance, first you would talk about the British biological studies of the 18th century, then about Moby Dick, published in 1851, then the book on sperm whales in other art (1968), and finally the biology articles (1980s) and the recent articles on American whaling of the 19th century. But there is relatively no continuity among subjects here. And notice that even though the sources on sperm whales in other art and on American whaling are written recently, they are about other subjects/objects that were created much earlier. Thus, the review loses its chronological focus.
• By publication: Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on biological studies of sperm whales if the progression revealed a change in dissection practices of the researchers who wrote and/or conducted the studies.
• By trend: A better way to organize the above sources chronologically is to examine the sources under another trend, such as the history of whaling. Then your review would have subsections according to eras within this period. For instance, the review might examine whaling from pre-1600-1699, 1700-1799, and 1800-1899. Under this method, you would combine the recent studies on American whaling in the 19th century with Moby Dick itself in the 1800-1899 category, even though the authors wrote a century apart.
• Thematic: Thematic reviews of literature are organized around a topic or issue, rather than the progression of time. However, progression of time may still be an important factor in a thematic review. For instance, the sperm whale review could focus on the development of the harpoon for whale hunting. While the study focuses on one topic, harpoon technology, it will still be organized chronologically. The only difference here between a “chronological” and a “thematic” approach is what is emphasized the most: the development of the harpoon or the harpoon technology.But more authentic thematic reviews tend to break away from chronological order. For instance, a thematic review of material on sperm whales might examine how they are portrayed as “evil” in cultural documents. The subsections might include how they are personified, how their proportions are exaggerated, and their behaviors misunderstood. A review organized in this manner would shift between time periods within each section according to the point made.
• Methodological: A methodological approach differs from the two above in that the focusing factor usually does not have to do with the content of the material. Instead, it focuses on the “methods” of the researcher or writer. For the sperm whale project, one methodological approach would be to look at cultural differences between the portrayal of whales in American, British, and French art work. Or the review might focus on the economic impact of whaling on a community. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed. Once you’ve decided on the organizational method for the body of the review, the sections you need to include in the paper should be easy to figure out. They should arise out of your organizational strategy. In other words, a chronological review would have subsections for each vital time period. A thematic review would have subtopics based upon factors that relate to the theme or issue.

Sometimes, though, you might need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. Put in only what is necessary. Here are a few other sections you might want to consider:

• Current Situation: Information necessary to understand the topic or focus of the literature review.
• History: The chronological progression of the field, the literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
• Methods and/or Standards: The criteria you used to select the sources in your literature review or the way in which you present your information. For instance, you might explain that your review includes only peer-reviewed articles and journals.

Questions for Further Research: What questions about the field has the review sparked? How will you further your research as a result of the review?

Begin composing

Once you’ve settled on a general pattern of organization, you’re ready to write each section. There are a few guidelines you should follow during the writing stage as well. Here is a sample paragraph from a literature review about sexism and language to illuminate the following discussion:

However, other studies have shown that even gender-neutral antecedents are more likely to produce masculine images than feminine ones (Gastil, 1990). Hamilton (1988) asked students to complete sentences that required them to fill in pronouns that agreed with gender-neutral antecedents such as “writer,” “pedestrian,” and “persons.” The students were asked to describe any image they had when writing the sentence. Hamilton found that people imagined 3.3 men to each woman in the masculine “generic” condition and 1.5 men per woman in the unbiased condition. Thus, while ambient sexism accounted for some of the masculine bias, sexist language amplified the effect. (Source: Erika Falk and Jordan Mills, “Why Sexist Language Affects Persuasion: The Role of Homophily, Intended Audience, and Offense,” Women and Language19:2).

Use evidence

In the example above, the writers refer to several other sources when making their point. A literature review in this sense is just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence to show that what you are saying is valid.

Be selective

Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the review’s focus, whether it is thematic, methodological, or chronological.

Use quotes sparingly

Falk and Mills do not use any direct quotes. That is because the survey nature of the literature review does not allow for in-depth discussion or detailed quotes from the text. Some short quotes here and there are okay, though, if you want to emphasize a point, or if what the author said just cannot be rewritten in your own words. Notice that Falk and Mills do quote certain terms that were coined by the author, not common knowledge, or taken directly from the study. But if you find yourself wanting to put in more quotes, check with your instructor.

Summarize and synthesize

Remember to summarize and synthesize your sources within each paragraph as well as throughout the review. The authors here recapitulate important features of Hamilton’s study, but then synthesize it by rephrasing the study’s significance and relating it to their own work.

Keep your own voice

While the literature review presents others’ ideas, your voice (the writer’s) should remain front and center. Notice that Falk and Mills weave references to other sources into their own text, but they still maintain their own voice by starting and ending the paragraph with their own ideas and their own words. The sources support what Falk and Mills are saying.

Use caution when paraphrasing

When paraphrasing a source that is not your own, be sure to represent the author’s information or opinions accurately and in your own words. In the preceding example, Falk and Mills either directly refer in the text to the author of their source, such as Hamilton, or they provide ample notation in the text when the ideas they are mentioning are not their own, for example, Gastil’s. For more information, please see our handout on plagiarism .

Revise, revise, revise

Draft in hand? Now you’re ready to revise. Spending a lot of time revising is a wise idea, because your main objective is to present the material, not the argument. So check over your review again to make sure it follows the assignment and/or your outline. Then, just as you would for most other academic forms of writing, rewrite or rework the language of your review so that you’ve presented your information in the most concise manner possible. Be sure to use terminology familiar to your audience; get rid of unnecessary jargon or slang. Finally, double check that you’ve documented your sources and formatted the review appropriately for your discipline. For tips on the revising and editing process, see our handout on revising drafts .

Works consulted

We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial . We revise these tips periodically and welcome feedback.

Anson, Chris M., and Robert A. Schwegler. 2010. The Longman Handbook for Writers and Readers , 6th ed. New York: Longman.

Jones, Robert, Patrick Bizzaro, and Cynthia Selfe. 1997. The Harcourt Brace Guide to Writing in the Disciplines . New York: Harcourt Brace.

Lamb, Sandra E. 1998. How to Write It: A Complete Guide to Everything You’ll Ever Write . Berkeley: Ten Speed Press.

Rosen, Leonard J., and Laurence Behrens. 2003. The Allyn & Bacon Handbook , 5th ed. New York: Longman.

Troyka, Lynn Quittman, and Doug Hesse. 2016. Simon and Schuster Handbook for Writers , 11th ed. London: Pearson.

You may reproduce it for non-commercial use if you use the entire handout and attribute the source: The Writing Center, University of North Carolina at Chapel Hill

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• UConn Library
• Literature Review: The What, Why and How-to Guide
• Introduction

Literature Review: The What, Why and How-to Guide — Introduction

• Getting Started
• How to Pick a Topic
• Strategies to Find Sources
• Evaluating Sources & Lit. Reviews
• Tips for Writing Literature Reviews
• Writing Literature Review: Useful Sites
• Citation Resources
• Other Academic Writings

What are Literature Reviews?

So, what is a literature review? "A literature review is an account of what has been published on a topic by accredited scholars and researchers. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries." Taylor, D.  The literature review: A few tips on conducting it . University of Toronto Health Sciences Writing Centre.

Goals of Literature Reviews

What are the goals of creating a Literature Review?  A literature could be written to accomplish different aims:

• To develop a theory or evaluate an existing theory
• To summarize the historical or existing state of a research topic
• Identify a problem in a field of research 

Baumeister, R. F., & Leary, M. R. (1997). Writing narrative literature reviews .  Review of General Psychology , 1 (3), 311-320.

What kinds of sources require a Literature Review?

• A research paper assigned in a course
• A thesis or dissertation
• A grant proposal
• An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

Types of Literature Reviews

What kinds of literature reviews are written?

Narrative review: The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

• Example : Predictors and Outcomes of U.S. Quality Maternity Leave: A Review and Conceptual Framework:  10.1177/08948453211037398  

Systematic review : "The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find." (p. 139). Nelson, L. K. (2013). Research in Communication Sciences and Disorders . Plural Publishing.

• Example : The effect of leave policies on increasing fertility: a systematic review:  10.1057/s41599-022-01270-w

Meta-analysis : "Meta-analysis is a method of reviewing research findings in a quantitative fashion by transforming the data from individual studies into what is called an effect size and then pooling and analyzing this information. The basic goal in meta-analysis is to explain why different outcomes have occurred in different studies." (p. 197). Roberts, M. C., & Ilardi, S. S. (2003). Handbook of Research Methods in Clinical Psychology . Blackwell Publishing.

• Example : Employment Instability and Fertility in Europe: A Meta-Analysis:  10.1215/00703370-9164737

Meta-synthesis : "Qualitative meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic." (p.312). Zimmer, L. (2006). Qualitative meta-synthesis: A question of dialoguing with texts .  Journal of Advanced Nursing , 53 (3), 311-318.

• Example : Women’s perspectives on career successes and barriers: A qualitative meta-synthesis:  10.1177/05390184221113735

Literature Reviews in the Health Sciences

• UConn Health subject guide on systematic reviews Explanation of the different review types used in health sciences literature as well as tools to help you find the right review type
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• Next: How to Pick a Topic >>
• Last Updated: Sep 21, 2022 2:16 PM
• URL: https://guides.lib.uconn.edu/literaturereview

Literature Review - what is a Literature Review, why it is important and how it is done

• Strategies to Find Sources

Evaluating Literature Reviews and Sources

Reading critically, tips to evaluate sources.

• Tips for Writing Literature Reviews
• Writing Literature Review: Useful Sites
• Citation Resources
• Other Academic Writings
• Useful Resources

A good literature review evaluates a wide variety of sources (academic articles, scholarly books, government/NGO reports). It also evaluates literature reviews that study similar topics. This page offers you a list of resources and tips on how to evaluate the sources that you may use to write your review.

• A Closer Look at Evaluating Literature Reviews Excerpt from the book chapter, “Evaluating Introductions and Literature Reviews” in Fred Pyrczak’s Evaluating Research in Academic Journals: A Practical Guide to Realistic Evaluation , (Chapter 4 and 5). This PDF discusses and offers great advice on how to evaluate "Introductions" and "Literature Reviews" by listing questions and tips. First part focus on Introductions and in page 10 in the PDF, 37 in the text, it focus on "literature reviews".
• Tips for Evaluating Sources (Print vs. Internet Sources) Excellent page that will guide you on what to ask to determine if your source is a reliable one. Check the other topics in the guide: Evaluating Bibliographic Citations and Evaluation During Reading on the left side menu.

To be able to write a good Literature Review, you need to be able to read critically. Below are some tips that will help you evaluate the sources for your paper.

Reading critically (summary from How to Read Academic Texts Critically)

• Who is the author? What is his/her standing in the field.
• What is the author’s purpose? To offer advice, make practical suggestions, solve a specific problem, to critique or clarify?
• Note the experts in the field: are there specific names/labs that are frequently cited?
• Pay attention to methodology: is it sound? what testing procedures, subjects, materials were used?
• Note conflicting theories, methodologies and results. Are there any assumptions being made by most/some researchers?
• Theories: have they evolved overtime?
• Evaluate and synthesize the findings and conclusions. How does this study contribute to your project?

Useful links:

• How to Read a Paper (University of Waterloo, Canada) This is an excellent paper that teach you how to read an academic paper, how to determine if it is something to set aside, or something to read deeply. Good advice to organize your literature for the Literature Review or just reading for classes.

Criteria to evaluate sources:

• Authority : Who is the author? what is his/her credentials--what university he/she is affliliated? Is his/her area of expertise?
• Usefulness : How this source related to your topic? How current or relevant it is to your topic?
• Reliability : Does the information comes from a reliable, trusted source such as an academic journal?

Useful site - Critically Analyzing Information Sources (Cornell University Library)

• << Previous: Strategies to Find Sources
• Next: Tips for Writing Literature Reviews >>
• Last Updated: Apr 10, 2024 3:27 PM
• URL: https://lit.libguides.com/Literature-Review

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What is a Literature Review? How to Write It (with Examples)

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

• What is the purpose of literature review? 
• a. Habitat Loss and Species Extinction: 
• b. Range Shifts and Phenological Changes: 
• c. Ocean Acidification and Coral Reefs: 
• d. Adaptive Strategies and Conservation Efforts: 

How to write a good literature review 

• Choose a Topic and Define the Research Question: 
• Decide on the Scope of Your Review: 
• Select Databases for Searches: 
• Conduct Searches and Keep Track: 
• Review the Literature: 
• Organize and Write Your Literature Review: 
• How to write a literature review faster with Paperpal? 
• Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

1. Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 

2. Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 

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3. Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 

4. Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 

5. Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 

6. Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

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Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

• Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
• Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
• Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
• Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
• Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

• Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
• Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
• Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
• Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
• Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

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Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

• Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
• Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
• Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
• Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
• Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

• Select a topic that is relevant to your field of study. 
• Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

• Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
• Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
• Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

• Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
• Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

• Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
• Record and document your search strategy for transparency and replicability. 
• Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

• Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
• Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
• Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
• Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
• Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

• Literature review outline should be based on themes, chronological order, or methodological approaches. 
• Write a clear and coherent narrative that synthesizes the information gathered. 
• Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
• Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

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How to write a literature review faster with Paperpal?

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Here’s how to use the Research feature:  

• Ask a question: Get started with a new document on paperpal.com. Click on the “Research” feature and type your question in plain English. Paperpal will scour over 250 million research articles, including conference papers and preprints, to provide you with accurate insights and citations. 
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• Cite with Confidence: Paperpal makes it easy to incorporate relevant citations and references into your writing, ensuring your arguments are well-supported by credible sources. This translates to a polished, well-researched literature review. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a good literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. By combining effortless research with an easy citation process, Paperpal Research streamlines the literature review process and empowers you to write faster and with more confidence. Try Paperpal Research now and see for yourself.  

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

References 

• Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
• Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
• Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

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Literature Review: Lit Review Sources

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Where do I find information for a literature review?

Research is done by...

...by way of...

...communicated through...

...and organized in...

Types of sources for a review...

• Primary source: Usually a report by the original researchers of a study (unfiltered sources)
• Secondary source: Description or summary by somebody other than the original researcher, e.g. a review article (filtered sources)
• Conceptual/theoretical: Papers concerned with description or analysis of theories or concepts associated with the topic
• Anecdotal/opinion/clinical: Views or opinions about the subject that are not research, review or theoretical (case studies or reports from clinical settings)

A Heirarchy of research information:

Source: SUNY Downstate Medical Center. Medical Research Library of Brooklyn. Evidence Based Medicine Course. A Guide to Research Methods: The Evidence Pyramid: http://library.downstate.edu/EBM2/2100.htm

Life Cycle of Publication

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Scientific information has a ‘life cycle’ of its own… it is born as an idea, and then matures and becomes more available to the public. First it appears within the so-called ‘invisible college’ of experts in the field, discussed at conferences and symposia or posted as pre-prints for comments and corrections. Then it appears in the published literature (the primary literature), often as a journal article in a peer-reviewed journal.

Researchers can use the indexing and alerting services of the secondary literature to find out what has been published in a field. Depending on how much information is added by the indexer or abstracter, this may take a few months (though electronic publication has sped up this process). Finally, the information may appear in more popular or reference sources, sometimes called the tertiary literature.

The person beginning a literature search may take this process in reverse: using tertiary sources for general background, then going to the secondary literature to survey what has been published, following up by finding the original (primary) sources, and generating their own research Idea.

(Original content by Wade Lee-Smith)

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Literature Review: The What, Why and How-to Guide: Evaluating Sources & Literature Reviews

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Evaluating Literature Reviews and Sources

• Tips for Evaluating Sources (Print vs. Internet Sources) Excellent page that will guide you on what to ask to determine if your source is a reliable one. Check the other topics in the guide: Evaluating Bibliographic Citations and Evaluation During Reading on the left side menu.

Criteria to evaluate sources:

• Authority : Who is the author? What are the author's credentials and areas of expertise? Is he or she affiliated with a university?
• Usefulness : How this source related to your topic? How current or relevant it is to your topic?
• Reliability : Does the information comes from a reliable, trusted source such as an academic journal?
• Critically Analyzing Information Sources: Critical Appraisal and Analysis (Cornell University Library) Ten things to look for when you evaluate an information source.

Reading Critically

Reading critically (summary from how to read academic texts critically).

• Who is the author? What is his/her standing in the field?
• What is the author’s purpose? To offer advice, make practical suggestions, solve a specific problem, critique or clarify?
• Note the experts in the field: are there specific names/labs that are frequently cited?
• Pay attention to methodology: is it sound? what testing procedures, subjects, materials were used?
• Note conflicting theories, methodologies, and results. Are there any assumptions being made by most/some researchers?
• Theories: have they evolved over time?
• Evaluate and synthesize the findings and conclusions. How does this study contribute to your project?
• How to Read Academic Texts Critically Excellent document about how best to read critically academic articles and other texts.
• How to Read an Academic Article This is an excellent paper that teach you how to read an academic paper, how to determine if it is something to set aside, or something to read deeply. Good advice to organize your literature for the Literature Review or just reading for classes.
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Literature Reviews

• What is a literature review?
• Steps in the Literature Review Process
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What is a Literature Review?

A literature or narrative review is a comprehensive review and analysis of the published literature on a specific topic or research question. The literature that is reviewed contains: books, articles, academic articles, conference proceedings, association papers, and dissertations. It contains the most pertinent studies and points to important past and current research and practices. It provides background and context, and shows how your research will contribute to the field. 

A literature review should: 

• Provide a comprehensive and updated review of the literature;
• Explain why this review has taken place;
• Articulate a position or hypothesis;
• Acknowledge and account for conflicting and corroborating points of view

From  S age Research Methods

Purpose of a Literature Review

A literature review can be written as an introduction to a study to:

• Demonstrate how a study fills a gap in research
• Compare a study with other research that's been done

Or it can be a separate work (a research article on its own) which:

• Organizes or describes a topic
• Describes variables within a particular issue/problem

Limitations of a Literature Review

Some of the limitations of a literature review are:

• It's a snapshot in time. Unlike other reviews, this one has beginning, a middle and an end. There may be future developments that could make your work less relevant.
• It may be too focused. Some niche studies may miss the bigger picture.
• It can be difficult to be comprehensive. There is no way to make sure all the literature on a topic was considered.
• It is easy to be biased if you stick to top tier journals. There may be other places where people are publishing exemplary research. Look to open access publications and conferences to reflect a more inclusive collection. Also, make sure to include opposing views (and not just supporting evidence).

Source: Grant, Maria J., and Andrew Booth. “A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies.” Health Information & Libraries Journal, vol. 26, no. 2, June 2009, pp. 91–108. Wiley Online Library, doi:10.1111/j.1471-1842.2009.00848.x.

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Larayne Dallas : Engineering

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For help in other subject areas, please see the guide to library specialists by subject .

Periodically, UT Libraries runs a workshop covering the basics and library support for literature reviews. While we try to offer these once per academic year, we find providing the recording to be helpful to community members who have missed the session. Following is the most recent recording of the workshop, Conducting a Literature Review. To view the recording, a UT login is required.

• October 26, 2022 recording
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Open Access

Peer-reviewed

Research Article

Functional connectivity changes in the brain of adolescents with internet addiction: A systematic literature review of imaging studies

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Software, Validation, Visualization, Writing – original draft, Writing – review & editing

Affiliation Child and Adolescent Mental Health, Department of Brain Sciences, Great Ormond Street Institute of Child Health, University College London, London, United Kingdom

Roles Conceptualization, Supervision, Validation, Writing – review & editing

* E-mail: [email protected]

Affiliation Behavioural Brain Sciences Unit, Population Policy Practice Programme, Great Ormond Street Institute of Child Health, University College London, London, United Kingdom

• Max L. Y. Chang, 
• Irene O. Lee

• Published: June 4, 2024
• https://doi.org/10.1371/journal.pmen.0000022
• Peer Review
• Reader Comments

Internet usage has seen a stark global rise over the last few decades, particularly among adolescents and young people, who have also been diagnosed increasingly with internet addiction (IA). IA impacts several neural networks that influence an adolescent’s behaviour and development. This article issued a literature review on the resting-state and task-based functional magnetic resonance imaging (fMRI) studies to inspect the consequences of IA on the functional connectivity (FC) in the adolescent brain and its subsequent effects on their behaviour and development. A systematic search was conducted from two databases, PubMed and PsycINFO, to select eligible articles according to the inclusion and exclusion criteria. Eligibility criteria was especially stringent regarding the adolescent age range (10–19) and formal diagnosis of IA. Bias and quality of individual studies were evaluated. The fMRI results from 12 articles demonstrated that the effects of IA were seen throughout multiple neural networks: a mix of increases/decreases in FC in the default mode network; an overall decrease in FC in the executive control network; and no clear increase or decrease in FC within the salience network and reward pathway. The FC changes led to addictive behaviour and tendencies in adolescents. The subsequent behavioural changes are associated with the mechanisms relating to the areas of cognitive control, reward valuation, motor coordination, and the developing adolescent brain. Our results presented the FC alterations in numerous brain regions of adolescents with IA leading to the behavioural and developmental changes. Research on this topic had a low frequency with adolescent samples and were primarily produced in Asian countries. Future research studies of comparing results from Western adolescent samples provide more insight on therapeutic intervention.

Citation: Chang MLY, Lee IO (2024) Functional connectivity changes in the brain of adolescents with internet addiction: A systematic literature review of imaging studies. PLOS Ment Health 1(1): e0000022. https://doi.org/10.1371/journal.pmen.0000022

Editor: Kizito Omona, Uganda Martyrs University, UGANDA

Received: December 29, 2023; Accepted: March 18, 2024; Published: June 4, 2024

Copyright: © 2024 Chang, Lee. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper and its Supporting information files.

Funding: The authors received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

Introduction

The behavioural addiction brought on by excessive internet use has become a rising source of concern [ 1 ] since the last decade. According to clinical studies, individuals with Internet Addiction (IA) or Internet Gaming Disorder (IGD) may have a range of biopsychosocial effects and is classified as an impulse-control disorder owing to its resemblance to pathological gambling and substance addiction [ 2 , 3 ]. IA has been defined by researchers as a person’s inability to resist the urge to use the internet, which has negative effects on their psychological well-being as well as their social, academic, and professional lives [ 4 ]. The symptoms can have serious physical and interpersonal repercussions and are linked to mood modification, salience, tolerance, impulsivity, and conflict [ 5 ]. In severe circumstances, people may experience severe pain in their bodies or health issues like carpal tunnel syndrome, dry eyes, irregular eating and disrupted sleep [ 6 ]. Additionally, IA is significantly linked to comorbidities with other psychiatric disorders [ 7 ].

Stevens et al (2021) reviewed 53 studies including 17 countries and reported the global prevalence of IA was 3.05% [ 8 ]. Asian countries had a higher prevalence (5.1%) than European countries (2.7%) [ 8 ]. Strikingly, adolescents and young adults had a global IGD prevalence rate of 9.9% which matches previous literature that reported historically higher prevalence among adolescent populations compared to adults [ 8 , 9 ]. Over 80% of adolescent population in the UK, the USA, and Asia have direct access to the internet [ 10 ]. Children and adolescents frequently spend more time on media (possibly 7 hours and 22 minutes per day) than at school or sleeping [ 11 ]. Developing nations have also shown a sharp rise in teenage internet usage despite having lower internet penetration rates [ 10 ]. Concerns regarding the possible harms that overt internet use could do to adolescents and their development have arisen because of this surge, especially the significant impacts by the COVID-19 pandemic [ 12 ]. The growing prevalence and neurocognitive consequences of IA among adolescents makes this population a vital area of study [ 13 ].

Adolescence is a crucial developmental stage during which people go through significant changes in their biology, cognition, and personalities [ 14 ]. Adolescents’ emotional-behavioural functioning is hyperactivated, which creates risk of psychopathological vulnerability [ 15 ]. In accordance with clinical study results [ 16 ], this emotional hyperactivity is supported by a high level of neuronal plasticity. This plasticity enables teenagers to adapt to the numerous physical and emotional changes that occur during puberty as well as develop communication techniques and gain independence [ 16 ]. However, the strong neuronal plasticity is also associated with risk-taking and sensation seeking [ 17 ] which may lead to IA.

Despite the fact that the precise neuronal mechanisms underlying IA are still largely unclear, functional magnetic resonance imaging (fMRI) method has been used by scientists as an important framework to examine the neuropathological changes occurring in IA, particularly in the form of functional connectivity (FC) [ 18 ]. fMRI research study has shown that IA alters both the functional and structural makeup of the brain [ 3 ].

We hypothesise that IA has widespread neurological alteration effects rather than being limited to a few specific brain regions. Further hypothesis holds that according to these alterations of FC between the brain regions or certain neural networks, adolescents with IA would experience behavioural changes. An investigation of these domains could be useful for creating better procedures and standards as well as minimising the negative effects of overt internet use. This literature review aims to summarise and analyse the evidence of various imaging studies that have investigated the effects of IA on the FC in adolescents. This will be addressed through two research questions:

• How does internet addiction affect the functional connectivity in the adolescent brain?
• How is adolescent behaviour and development impacted by functional connectivity changes due to internet addiction?

The review protocol was conducted in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (see S1 Checklist ).

Search strategy and selection process

A systematic search was conducted up until April 2023 from two sources of database, PubMed and PsycINFO, using a range of terms relevant to the title and research questions (see full list of search terms in S1 Appendix ). All the searched articles can be accessed in the S1 Data . The eligible articles were selected according to the inclusion and exclusion criteria. Inclusion criteria used for the present review were: (i) participants in the studies with clinical diagnosis of IA; (ii) participants between the ages of 10 and 19; (iii) imaging research investigations; (iv) works published between January 2013 and April 2023; (v) written in English language; (vi) peer-reviewed papers and (vii) full text. The numbers of articles excluded due to not meeting the inclusion criteria are shown in Fig 1 . Each study’s title and abstract were screened for eligibility.

• PPT PowerPoint slide
• PNG larger image
• TIFF original image

https://doi.org/10.1371/journal.pmen.0000022.g001

Quality appraisal

Full texts of all potentially relevant studies were then retrieved and further appraised for eligibility. Furthermore, articles were critically appraised based on the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) framework to evaluate the individual study for both quality and bias. The subsequent quality levels were then appraised to each article and listed as either low, moderate, or high.

Data collection process

Data that satisfied the inclusion requirements was entered into an excel sheet for data extraction and further selection. An article’s author, publication year, country, age range, participant sample size, sex, area of interest, measures, outcome and article quality were all included in the data extraction spreadsheet. Studies looking at FC, for instance, were grouped, while studies looking at FC in specific area were further divided into sub-groups.

Data synthesis and analysis

Articles were classified according to their location in the brain as well as the network or pathway they were a part of to create a coherent narrative between the selected studies. Conclusions concerning various research trends relevant to particular groupings were drawn from these groupings and subgroupings. To maintain the offered information in a prominent manner, these assertions were entered into the data extraction excel spreadsheet.

With the search performed on the selected databases, 238 articles in total were identified (see Fig 1 ). 15 duplicated articles were eliminated, and another 6 items were removed for various other reasons. Title and abstract screening eliminated 184 articles because they were not in English (number of article, n, = 7), did not include imaging components (n = 47), had adult participants (n = 53), did not have a clinical diagnosis of IA (n = 19), did not address FC in the brain (n = 20), and were published outside the desired timeframe (n = 38). A further 21 papers were eliminated for failing to meet inclusion requirements after the remaining 33 articles underwent full-text eligibility screening. A total of 12 papers were deemed eligible for this review analysis.

Characteristics of the included studies, as depicted in the data extraction sheet in Table 1 provide information of the author(s), publication year, sample size, study location, age range, gender, area of interest, outcome, measures used and quality appraisal. Most of the studies in this review utilised resting state functional magnetic resonance imaging techniques (n = 7), with several studies demonstrating task-based fMRI procedures (n = 3), and the remaining studies utilising whole-brain imaging measures (n = 2). The studies were all conducted in Asiatic countries, specifically coming from China (8), Korea (3), and Indonesia (1). Sample sizes ranged from 12 to 31 participants with most of the imaging studies having comparable sample sizes. Majority of the studies included a mix of male and female participants (n = 8) with several studies having a male only participant pool (n = 3). All except one of the mixed gender studies had a majority male participant pool. One study did not disclose their data on the gender demographics of their experiment. Study years ranged from 2013–2022, with 2 studies in 2013, 3 studies in 2014, 3 studies in 2015, 1 study in 2017, 1 study in 2020, 1 study in 2021, and 1 study in 2022.

https://doi.org/10.1371/journal.pmen.0000022.t001

(1) How does internet addiction affect the functional connectivity in the adolescent brain?

The included studies were organised according to the brain region or network that they were observing. The specific networks affected by IA were the default mode network, executive control system, salience network and reward pathway. These networks are vital components of adolescent behaviour and development [ 31 ]. The studies in each section were then grouped into subsections according to their specific brain regions within their network.

Default mode network (DMN)/reward network.

Out of the 12 studies, 3 have specifically studied the default mode network (DMN), and 3 observed whole-brain FC that partially included components of the DMN. The effect of IA on the various centres of the DMN was not unilaterally the same. The findings illustrate a complex mix of increases and decreases in FC depending on the specific region in the DMN (see Table 2 and Fig 2 ). The alteration of FC in posterior cingulate cortex (PCC) in the DMN was the most frequently reported area in adolescents with IA, which involved in attentional processes [ 32 ], but Lee et al. (2020) additionally found alterations of FC in other brain regions, such as anterior insula cortex, a node in the DMN that controls the integration of motivational and cognitive processes [ 20 ].

https://doi.org/10.1371/journal.pmen.0000022.g002

The overall changes of functional connectivity in the brain network including default mode network (DMN), executive control network (ECN), salience network (SN) and reward network. IA = Internet Addiction, FC = Functional Connectivity.

https://doi.org/10.1371/journal.pmen.0000022.t002

Ding et al. (2013) revealed altered FC in the cerebellum, the middle temporal gyrus, and the medial prefrontal cortex (mPFC) [ 22 ]. They found that the bilateral inferior parietal lobule, left superior parietal lobule, and right inferior temporal gyrus had decreased FC, while the bilateral posterior lobe of the cerebellum and the medial temporal gyrus had increased FC [ 22 ]. The right middle temporal gyrus was found to have 111 cluster voxels (t = 3.52, p<0.05) and the right inferior parietal lobule was found to have 324 cluster voxels (t = -4.07, p<0.05) with an extent threshold of 54 voxels (figures above this threshold are deemed significant) [ 22 ]. Additionally, there was a negative correlation, with 95 cluster voxels (p<0.05) between the FC of the left superior parietal lobule and the PCC with the Chen Internet Addiction Scores (CIAS) which are used to determine the severity of IA [ 22 ]. On the other hand, in regions of the reward system, connection with the PCC was positively connected with CIAS scores [ 22 ]. The most significant was the right praecuneus with 219 cluster voxels (p<0.05) [ 22 ]. Wang et al. (2017) also discovered that adolescents with IA had 33% less FC in the left inferior parietal lobule and 20% less FC in the dorsal mPFC [ 24 ]. A potential connection between the effects of substance use and overt internet use is revealed by the generally decreased FC in these areas of the DMN of teenagers with drug addiction and IA [ 35 ].

The putamen was one of the main regions of reduced FC in adolescents with IA [ 19 ]. The putamen and the insula-operculum demonstrated significant group differences regarding functional connectivity with a cluster size of 251 and an extent threshold of 250 (Z = 3.40, p<0.05) [ 19 ]. The molecular mechanisms behind addiction disorders have been intimately connected to decreased striatal dopaminergic function [ 19 ], making this function crucial.

Executive Control Network (ECN).

5 studies out of 12 have specifically viewed parts of the executive control network (ECN) and 3 studies observed whole-brain FC. The effects of IA on the ECN’s constituent parts were consistent across all the studies examined for this analysis (see Table 2 and Fig 3 ). The results showed a notable decline in all the ECN’s major centres. Li et al. (2014) used fMRI imaging and a behavioural task to study response inhibition in adolescents with IA [ 25 ] and found decreased activation at the striatum and frontal gyrus, particularly a reduction in FC at inferior frontal gyrus, in the IA group compared to controls [ 25 ]. The inferior frontal gyrus showed a reduction in FC in comparison to the controls with a cluster size of 71 (t = 4.18, p<0.05) [ 25 ]. In addition, the frontal-basal ganglia pathways in the adolescents with IA showed little effective connection between areas and increased degrees of response inhibition [ 25 ].

https://doi.org/10.1371/journal.pmen.0000022.g003

Lin et al. (2015) found that adolescents with IA demonstrated disrupted corticostriatal FC compared to controls [ 33 ]. The corticostriatal circuitry experienced decreased connectivity with the caudate, bilateral anterior cingulate cortex (ACC), as well as the striatum and frontal gyrus [ 33 ]. The inferior ventral striatum showed significantly reduced FC with the subcallosal ACC and caudate head with cluster size of 101 (t = -4.64, p<0.05) [ 33 ]. Decreased FC in the caudate implies dysfunction of the corticostriatal-limbic circuitry involved in cognitive and emotional control [ 36 ]. The decrease in FC in both the striatum and frontal gyrus is related to inhibitory control, a common deficit seen with disruptions with the ECN [ 33 ].

The dorsolateral prefrontal cortex (DLPFC), ACC, and right supplementary motor area (SMA) of the prefrontal cortex were all found to have significantly decreased grey matter volume [ 29 ]. In addition, the DLPFC, insula, temporal cortices, as well as significant subcortical regions like the striatum and thalamus, showed decreased FC [ 29 ]. According to Tremblay (2009), the striatum plays a significant role in the processing of rewards, decision-making, and motivation [ 37 ]. Chen et al. (2020) reported that the IA group demonstrated increased impulsivity as well as decreased reaction inhibition using a Stroop colour-word task [ 26 ]. Furthermore, Chen et al. (2020) observed that the left DLPFC and dorsal striatum experienced a negative connection efficiency value, specifically demonstrating that the dorsal striatum activity suppressed the left DLPFC [ 27 ].

Salience network (SN).

Out of the 12 chosen studies, 3 studies specifically looked at the salience network (SN) and 3 studies have observed whole-brain FC. Relative to the DMN and ECN, the findings on the SN were slightly sparser. Despite this, adolescents with IA demonstrated a moderate decrease in FC, as well as other measures like fibre connectivity and cognitive control, when compared to healthy control (see Table 2 and Fig 4 ).

https://doi.org/10.1371/journal.pmen.0000022.g004

Xing et al. (2014) used both dorsal anterior cingulate cortex (dACC) and insula to test FC changes in the SN of adolescents with IA and found decreased structural connectivity in the SN as well as decreased fractional anisotropy (FA) that correlated to behaviour performance in the Stroop colour word-task [ 21 ]. They examined the dACC and insula to determine whether the SN’s disrupted connectivity may be linked to the SN’s disruption of regulation, which would explain the impaired cognitive control seen in adolescents with IA. However, researchers did not find significant FC differences in the SN when compared to the controls [ 21 ]. These results provided evidence for the structural changes in the interconnectivity within SN in adolescents with IA.

Wang et al. (2017) investigated network interactions between the DMN, ECN, SN and reward pathway in IA subjects [ 24 ] (see Fig 5 ), and found 40% reduction of FC between the DMN and specific regions of the SN, such as the insula, in comparison to the controls (p = 0.008) [ 24 ]. The anterior insula and dACC are two areas that are impacted by this altered FC [ 24 ]. This finding supports the idea that IA has similar neurobiological abnormalities with other addictive illnesses, which is in line with a study that discovered disruptive changes in the SN and DMN’s interaction in cocaine addiction [ 38 ]. The insula has also been linked to the intensity of symptoms and has been implicated in the development of IA [ 39 ].

“+” indicates an increase in behaivour; “-”indicates a decrease in behaviour; solid arrows indicate a direct network interaction; and the dotted arrows indicates a reduction in network interaction. This diagram depicts network interactions juxtaposed with engaging in internet related behaviours. Through the neural interactions, the diagram illustrates how the networks inhibit or amplify internet usage and vice versa. Furthermore, it demonstrates how the SN mediates both the DMN and ECN.

https://doi.org/10.1371/journal.pmen.0000022.g005

(2) How is adolescent behaviour and development impacted by functional connectivity changes due to internet addiction?

The findings that IA individuals demonstrate an overall decrease in FC in the DMN is supported by numerous research [ 24 ]. Drug addict populations also exhibited similar decline in FC in the DMN [ 40 ]. The disruption of attentional orientation and self-referential processing for both substance and behavioural addiction was then hypothesised to be caused by DMN anomalies in FC [ 41 ].

In adolescents with IA, decline of FC in the parietal lobule affects visuospatial task-related behaviour [ 22 ], short-term memory [ 42 ], and the ability of controlling attention or restraining motor responses during response inhibition tests [ 42 ]. Cue-induced gaming cravings are influenced by the DMN [ 43 ]. A visual processing area called the praecuneus links gaming cues to internal information [ 22 ]. A meta-analysis found that the posterior cingulate cortex activity of individuals with IA during cue-reactivity tasks was connected with their gaming time [ 44 ], suggesting that excessive gaming may impair DMN function and that individuals with IA exert more cognitive effort to control it. Findings for the behavioural consequences of FC changes in the DMN illustrate its underlying role in regulating impulsivity, self-monitoring, and cognitive control.

Furthermore, Ding et al. (2013) reported an activation of components of the reward pathway, including areas like the nucleus accumbens, praecuneus, SMA, caudate, and thalamus, in connection to the DMN [ 22 ]. The increased FC of the limbic and reward networks have been confirmed to be a major biomarker for IA [ 45 , 46 ]. The increased reinforcement in these networks increases the strength of reward stimuli and makes it more difficult for other networks, namely the ECN, to down-regulate the increased attention [ 29 ] (See Fig 5 ).

Executive control network (ECN).

The numerous IA-affected components in the ECN have a role in a variety of behaviours that are connected to both response inhibition and emotional regulation [ 47 ]. For instance, brain regions like the striatum, which are linked to impulsivity and the reward system, are heavily involved in the act of playing online games [ 47 ]. Online game play activates the striatum, which suppresses the left DLPFC in ECN [ 48 ]. As a result, people with IA may find it difficult to control their want to play online games [ 48 ]. This system thus causes impulsive and protracted gaming conduct, lack of inhibitory control leading to the continued use of internet in an overt manner despite a variety of negative effects, personal distress, and signs of psychological dependence [ 33 ] (See Fig 5 ).

Wang et al. (2017) report that disruptions in cognitive control networks within the ECN are frequently linked to characteristics of substance addiction [ 24 ]. With samples that were addicted to heroin and cocaine, previous studies discovered abnormal FC in the ECN and the PFC [ 49 ]. Electronic gaming is known to promote striatal dopamine release, similar to drug addiction [ 50 ]. According to Drgonova and Walther (2016), it is hypothesised that dopamine could stimulate the reward system of the striatum in the brain, leading to a loss of impulse control and a failure of prefrontal lobe executive inhibitory control [ 51 ]. In the end, IA’s resemblance to drug use disorders may point to vital biomarkers or underlying mechanisms that explain how cognitive control and impulsive behaviour are related.

A task-related fMRI study found that the decrease in FC between the left DLPFC and dorsal striatum was congruent with an increase in impulsivity in adolescents with IA [ 26 ]. The lack of response inhibition from the ECN results in a loss of control over internet usage and a reduced capacity to display goal-directed behaviour [ 33 ]. Previous studies have linked the alteration of the ECN in IA with higher cue reactivity and impaired ability to self-regulate internet specific stimuli [ 52 ].

Salience network (SN)/ other networks.

Xing et al. (2014) investigated the significance of the SN regarding cognitive control in teenagers with IA [ 21 ]. The SN, which is composed of the ACC and insula, has been demonstrated to control dynamic changes in other networks to modify cognitive performance [ 21 ]. The ACC is engaged in conflict monitoring and cognitive control, according to previous neuroimaging research [ 53 ]. The insula is a region that integrates interoceptive states into conscious feelings [ 54 ]. The results from Xing et al. (2014) showed declines in the SN regarding its structural connectivity and fractional anisotropy, even though they did not observe any appreciable change in FC in the IA participants [ 21 ]. Due to the small sample size, the results may have indicated that FC methods are not sensitive enough to detect the significant functional changes [ 21 ]. However, task performance behaviours associated with impaired cognitive control in adolescents with IA were correlated with these findings [ 21 ]. Our comprehension of the SN’s broader function in IA can be enhanced by this relationship.

Research study supports the idea that different psychological issues are caused by the functional reorganisation of expansive brain networks, such that strong association between SN and DMN may provide neurological underpinnings at the system level for the uncontrollable character of internet-using behaviours [ 24 ]. In the study by Wang et al. (2017), the decreased interconnectivity between the SN and DMN, comprising regions such the DLPFC and the insula, suggests that adolescents with IA may struggle to effectively inhibit DMN activity during internally focused processing, leading to poorly managed desires or preoccupations to use the internet [ 24 ] (See Fig 5 ). Subsequently, this may cause a failure to inhibit DMN activity as well as a restriction of ECN functionality [ 55 ]. As a result, the adolescent experiences an increased salience and sensitivity towards internet addicting cues making it difficult to avoid these triggers [ 56 ].

The primary aim of this review was to present a summary of how internet addiction impacts on the functional connectivity of adolescent brain. Subsequently, the influence of IA on the adolescent brain was compartmentalised into three sections: alterations of FC at various brain regions, specific FC relationships, and behavioural/developmental changes. Overall, the specific effects of IA on the adolescent brain were not completely clear, given the variety of FC changes. However, there were overarching behavioural, network and developmental trends that were supported that provided insight on adolescent development.

The first hypothesis that was held about this question was that IA was widespread and would be regionally similar to substance-use and gambling addiction. After conducting a review of the information in the chosen articles, the hypothesis was predictably supported. The regions of the brain affected by IA are widespread and influence multiple networks, mainly DMN, ECN, SN and reward pathway. In the DMN, there was a complex mix of increases and decreases within the network. However, in the ECN, the alterations of FC were more unilaterally decreased, but the findings of SN and reward pathway were not quite clear. Overall, the FC changes within adolescents with IA are very much network specific and lay a solid foundation from which to understand the subsequent behaviour changes that arise from the disorder.

The second hypothesis placed emphasis on the importance of between network interactions and within network interactions in the continuation of IA and the development of its behavioural symptoms. The results from the findings involving the networks, DMN, SN, ECN and reward system, support this hypothesis (see Fig 5 ). Studies confirm the influence of all these neural networks on reward valuation, impulsivity, salience to stimuli, cue reactivity and other changes that alter behaviour towards the internet use. Many of these changes are connected to the inherent nature of the adolescent brain.

There are multiple explanations that underlie the vulnerability of the adolescent brain towards IA related urges. Several of them have to do with the inherent nature and underlying mechanisms of the adolescent brain. Children’s emotional, social, and cognitive capacities grow exponentially during childhood and adolescence [ 57 ]. Early teenagers go through a process called “social reorientation” that is characterised by heightened sensitivity to social cues and peer connections [ 58 ]. Adolescents’ improvements in their social skills coincide with changes in their brains’ anatomical and functional organisation [ 59 ]. Functional hubs exhibit growing connectivity strength [ 60 ], suggesting increased functional integration during development. During this time, the brain’s functional networks change from an anatomically dominant structure to a scattered architecture [ 60 ].

The adolescent brain is very responsive to synaptic reorganisation and experience cues [ 61 ]. As a result, one of the distinguishing traits of the maturation of adolescent brains is the variation in neural network trajectory [ 62 ]. Important weaknesses of the adolescent brain that may explain the neurobiological change brought on by external stimuli are illustrated by features like the functional gaps between networks and the inadequate segregation of networks [ 62 ].

The implications of these findings towards adolescent behaviour are significant. Although the exact changes and mechanisms are not fully clear, the observed changes in functional connectivity have the capacity of influencing several aspects of adolescent development. For example, functional connectivity has been utilised to investigate attachment styles in adolescents [ 63 ]. It was observed that adolescent attachment styles were negatively associated with caudate-prefrontal connectivity, but positively with the putamen-visual area connectivity [ 63 ]. Both named areas were also influenced by the onset of internet addiction, possibly providing a connection between the two. Another study associated neighbourhood/socioeconomic disadvantage with functional connectivity alterations in the DMN and dorsal attention network [ 64 ]. The study also found multivariate brain behaviour relationships between the altered/disadvantaged functional connectivity and mental health and cognition [ 64 ]. This conclusion supports the notion that the functional connectivity alterations observed in IA are associated with specific adolescent behaviours as well as the fact that functional connectivity can be utilised as a platform onto which to compare various neurologic conditions.

Limitations/strengths

There were several limitations that were related to the conduction of the review as well as the data extracted from the articles. Firstly, the study followed a systematic literature review design when analysing the fMRI studies. The data pulled from these imaging studies were namely qualitative and were subject to bias contrasting the quantitative nature of statistical analysis. Components of the study, such as sample sizes, effect sizes, and demographics were not weighted or controlled. The second limitation brought up by a similar review was the lack of a universal consensus of terminology given IA [ 47 ]. Globally, authors writing about this topic use an array of terminology including online gaming addiction, internet addiction, internet gaming disorder, and problematic internet use. Often, authors use multiple terms interchangeably which makes it difficult to depict the subtle similarities and differences between the terms.

Reviewing the explicit limitations in each of the included studies, two major limitations were brought up in many of the articles. One was relating to the cross-sectional nature of the included studies. Due to the inherent qualities of a cross-sectional study, the studies did not provide clear evidence that IA played a causal role towards the development of the adolescent brain. While several biopsychosocial factors mediate these interactions, task-based measures that combine executive functions with imaging results reinforce the assumed connection between the two that is utilised by the papers studying IA. Another limitation regarded the small sample size of the included studies, which averaged to around 20 participants. The small sample size can influence the generalisation of the results as well as the effectiveness of statistical analyses. Ultimately, both included study specific limitations illustrate the need for future studies to clarify the causal relationship between the alterations of FC and the development of IA.

Another vital limitation was the limited number of studies applying imaging techniques for investigations on IA in adolescents were a uniformly Far East collection of studies. The reason for this was because the studies included in this review were the only fMRI studies that were found that adhered to the strict adolescent age restriction. The adolescent age range given by the WHO (10–19 years old) [ 65 ] was strictly followed. It is important to note that a multitude of studies found in the initial search utilised an older adolescent demographic that was slightly higher than the WHO age range and had a mean age that was outside of the limitations. As a result, the results of this review are biased and based on the 12 studies that met the inclusion and exclusion criteria.

Regarding the global nature of the research, although the journals that the studies were published in were all established western journals, the collection of studies were found to all originate from Asian countries, namely China and Korea. Subsequently, it pulls into question if the results and measures from these studies are generalisable towards a western population. As stated previously, Asian countries have a higher prevalence of IA, which may be the reasoning to why the majority of studies are from there [ 8 ]. However, in an additional search including other age groups, it was found that a high majority of all FC studies on IA were done in Asian countries. Interestingly, western papers studying fMRI FC were primarily focused on gambling and substance-use addiction disorders. The western papers on IA were less focused on fMRI FC but more on other components of IA such as sleep, game-genre, and other non-imaging related factors. This demonstrated an overall lack of western fMRI studies on IA. It is important to note that both western and eastern fMRI studies on IA presented an overall lack on children and adolescents in general.

Despite the several limitations, this review provided a clear reflection on the state of the data. The strengths of the review include the strict inclusion/exclusion criteria that filtered through studies and only included ones that contained a purely adolescent sample. As a result, the information presented in this review was specific to the review’s aims. Given the sparse nature of adolescent specific fMRI studies on the FC changes in IA, this review successfully provided a much-needed niche representation of adolescent specific results. Furthermore, the review provided a thorough functional explanation of the DMN, ECN, SN and reward pathway making it accessible to readers new to the topic.

Future directions and implications

Through the search process of the review, there were more imaging studies focused on older adolescence and adulthood. Furthermore, finding a review that covered a strictly adolescent population, focused on FC changes, and was specifically depicting IA, was proven difficult. Many related reviews, such as Tereshchenko and Kasparov (2019), looked at risk factors related to the biopsychosocial model, but did not tackle specific alterations in specific structural or functional changes in the brain [ 66 ]. Weinstein (2017) found similar structural and functional results as well as the role IA has in altering response inhibition and reward valuation in adolescents with IA [ 47 ]. Overall, the accumulated findings only paint an emerging pattern which aligns with similar substance-use and gambling disorders. Future studies require more specificity in depicting the interactions between neural networks, as well as more literature on adolescent and comorbid populations. One future field of interest is the incorporation of more task-based fMRI data. Advances in resting-state fMRI methods have yet to be reflected or confirmed in task-based fMRI methods [ 62 ]. Due to the fact that network connectivity is shaped by different tasks, it is critical to confirm that the findings of the resting state fMRI studies also apply to the task based ones [ 62 ]. Subsequently, work in this area will confirm if intrinsic connectivity networks function in resting state will function similarly during goal directed behaviour [ 62 ]. An elevated focus on adolescent populations as well as task-based fMRI methodology will help uncover to what extent adolescent network connectivity maturation facilitates behavioural and cognitive development [ 62 ].

A treatment implication is the potential usage of bupropion for the treatment of IA. Bupropion has been previously used to treat patients with gambling disorder and has been effective in decreasing overall gambling behaviour as well as money spent while gambling [ 67 ]. Bae et al. (2018) found a decrease in clinical symptoms of IA in line with a 12-week bupropion treatment [ 31 ]. The study found that bupropion altered the FC of both the DMN and ECN which in turn decreased impulsivity and attentional deficits for the individuals with IA [ 31 ]. Interventions like bupropion illustrate the importance of understanding the fundamental mechanisms that underlie disorders like IA.

The goal for this review was to summarise the current literature on functional connectivity changes in adolescents with internet addiction. The findings answered the primary research questions that were directed at FC alterations within several networks of the adolescent brain and how that influenced their behaviour and development. Overall, the research demonstrated several wide-ranging effects that influenced the DMN, SN, ECN, and reward centres. Additionally, the findings gave ground to important details such as the maturation of the adolescent brain, the high prevalence of Asian originated studies, and the importance of task-based studies in this field. The process of making this review allowed for a thorough understanding IA and adolescent brain interactions.

Given the influx of technology and media in the lives and education of children and adolescents, an increase in prevalence and focus on internet related behavioural changes is imperative towards future children/adolescent mental health. Events such as COVID-19 act to expose the consequences of extended internet usage on the development and lifestyle of specifically young people. While it is important for parents and older generations to be wary of these changes, it is important for them to develop a base understanding of the issue and not dismiss it as an all-bad or all-good scenario. Future research on IA will aim to better understand the causal relationship between IA and psychological symptoms that coincide with it. The current literature regarding functional connectivity changes in adolescents is limited and requires future studies to test with larger sample sizes, comorbid populations, and populations outside Far East Asia.

This review aimed to demonstrate the inner workings of how IA alters the connection between the primary behavioural networks in the adolescent brain. Predictably, the present answers merely paint an unfinished picture that does not necessarily depict internet usage as overwhelmingly positive or negative. Alternatively, the research points towards emerging patterns that can direct individuals on the consequences of certain variables or risk factors. A clearer depiction of the mechanisms of IA would allow physicians to screen and treat the onset of IA more effectively. Clinically, this could be in the form of more streamlined and accurate sessions of CBT or family therapy, targeting key symptoms of IA. Alternatively clinicians could potentially prescribe treatment such as bupropion to target FC in certain regions of the brain. Furthermore, parental education on IA is another possible avenue of prevention from a public health standpoint. Parents who are aware of the early signs and onset of IA will more effectively handle screen time, impulsivity, and minimize the risk factors surrounding IA.

Additionally, an increased attention towards internet related fMRI research is needed in the West, as mentioned previously. Despite cultural differences, Western countries may hold similarities to the eastern countries with a high prevalence of IA, like China and Korea, regarding the implications of the internet and IA. The increasing influence of the internet on the world may contribute to an overall increase in the global prevalence of IA. Nonetheless, the high saturation of eastern studies in this field should be replicated with a Western sample to determine if the same FC alterations occur. A growing interest in internet related research and education within the West will hopefully lead to the knowledge of healthier internet habits and coping strategies among parents with children and adolescents. Furthermore, IA research has the potential to become a crucial proxy for which to study adolescent brain maturation and development.

Supporting information

S1 checklist. prisma checklist..

https://doi.org/10.1371/journal.pmen.0000022.s001

S1 Appendix. Search strategies with all the terms.

https://doi.org/10.1371/journal.pmen.0000022.s002

S1 Data. Article screening records with details of categorized content.

https://doi.org/10.1371/journal.pmen.0000022.s003

Acknowledgments

The authors thank https://www.stockio.com/free-clipart/brain-01 (with attribution to Stockio.com); and https://www.rawpixel.com/image/6442258/png-sticker-vintage for the free images used to create Figs 2 – 4 .

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• Introduction
• Conclusions
• Article Information

Evidence reviews for the US Preventive Services Task Force (USPSTF) use an analytic framework to visually display the key questions that the review will address to allow the USPSTF to evaluate the effectiveness and safety of a preventive service. The questions are depicted by linkages that relate interventions and outcomes. A dashed line indicates a health outcome that immediately follows an intermediate outcome. The contextual questions (CQs) are also listed; they were not a part of this systematic review. They are intended to provide additional background information. For additional information, see the USPSTF Procedure Manual. 12 BMI indicates body mass index; FPG, fasting plasma glucose; HbA 1c , hemoglobin A 1c .

a Eligible interventions included pharmacotherapy and primary care–relevant counseling focused on healthy diet and nutrition, physical activity, or both.

KQ indicates key question.

a Number of studies per KQ sums to more than the total number of studies because some studies were applicable to multiple KQs.

eIntroduction

eTable 1. Classification of Diabetes

eTable 2. Criteria for the Diagnosis of Type 2 Diabetes and Prediabetes

eTable 3. Eligibility Criteria

eTable 4. Quality Assessment of Randomized Controlled Clinical Trials (All KQs)

eTable 5. Quality Assessment of Randomized Controlled Clinical Trials (All KQs)

eTable 6. Quality Assessment of Randomized Controlled Clinical Trials: Additional Questions for Studies Reporting Harms (KQ2 and KQ4 only)

eContextual Questions

eTable 7. Studies That Compared Agreement among Screening Tests, by Comparison

eReferences

• USPSTF Recommendation: Screening for Prediabetes and Diabetes in Children and Adolescents JAMA US Preventive Services Task Force September 13, 2022 This 2022 Recommendation Statement from the US Preventive Services Task Force concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for type 2 diabetes in children and adolescents (I statement). US Preventive Services Task Force; Carol M. Mangione, MD, MSPH; Michael J. Barry, MD; Wanda K. Nicholson, MD, MPH, MBA; Michael Cabana, MD, MA, MPH; David Chelmow, MD; Tumaini Rucker Coker, MD, MBA; Karina W. Davidson, PhD, MASc; Esa M. Davis, MD, MPH; Katrina E. Donahue, MD, MPH; Carlos Roberto Jaén, MD, PhD, MS; Martha Kubik, PhD, RN; Li Li, MD, PhD, MPH; Gbenga Ogedegbe, MD, MPH; Lori Pbert, PhD; John M. Ruiz, PhD; James Stevermer, MD, MSPH; Chien-Wen Tseng, MD, MPH, MSEE; John B. Wong, MD
• Recommendations for Screening Children and Adolescents for Prediabetes and Type 2 Diabetes JAMA Editorial September 13, 2022 Elvira Isganaitis, MD, MPH; Lori Laffel, MD, MPH
• Patient Information: Screening for Type 2 Diabetes in Children and Adolescents JAMA JAMA Patient Page September 13, 2022 This JAMA Patient Page summarizes the US Preventive Services Task Force’s recent recommendations on screening for type 2 diabetes in children and adolescents. Jill Jin, MD, MPH
• Broader Screening for Youth-Onset Type 2 Diabetes JAMA Network Open Editorial September 13, 2022 Amy S. Shah, MD, MS; Kristen J. Nadeau, MD, MS; Megan M. Kelsey, MD, MS

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Jonas DE , Vander Schaaf EB , Riley S, et al. Screening for Prediabetes and Type 2 Diabetes in Children and Adolescents : Evidence Report and Systematic Review for the US Preventive Services Task Force . JAMA. 2022;328(10):968–979. doi:10.1001/jama.2022.7957

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Screening for Prediabetes and Type 2 Diabetes in Children and Adolescents : Evidence Report and Systematic Review for the US Preventive Services Task Force

• 1 RTI International–University of North Carolina at Chapel Hill Evidence-based Practice Center
• 2 Department of Internal Medicine, The Ohio State University, Columbus
• 3 Department of Pediatrics, University of North Carolina School of Medicine, Chapel Hill
• 4 Cecil G. Sheps Center for Health Services Research, University of North Carolina at Chapel Hill
• 5 RTI International, Research Triangle Park, North Carolina
• 6 Kaiser Permanente Center for Health Research, Portland, Oregon
• Editorial Recommendations for Screening Children and Adolescents for Prediabetes and Type 2 Diabetes Elvira Isganaitis, MD, MPH; Lori Laffel, MD, MPH JAMA
• Editorial Broader Screening for Youth-Onset Type 2 Diabetes Amy S. Shah, MD, MS; Kristen J. Nadeau, MD, MS; Megan M. Kelsey, MD, MS JAMA Network Open
• US Preventive Services Task Force USPSTF Recommendation: Screening for Prediabetes and Diabetes in Children and Adolescents US Preventive Services Task Force; Carol M. Mangione, MD, MSPH; Michael J. Barry, MD; Wanda K. Nicholson, MD, MPH, MBA; Michael Cabana, MD, MA, MPH; David Chelmow, MD; Tumaini Rucker Coker, MD, MBA; Karina W. Davidson, PhD, MASc; Esa M. Davis, MD, MPH; Katrina E. Donahue, MD, MPH; Carlos Roberto Jaén, MD, PhD, MS; Martha Kubik, PhD, RN; Li Li, MD, PhD, MPH; Gbenga Ogedegbe, MD, MPH; Lori Pbert, PhD; John M. Ruiz, PhD; James Stevermer, MD, MSPH; Chien-Wen Tseng, MD, MPH, MSEE; John B. Wong, MD JAMA
• JAMA Patient Page Patient Information: Screening for Type 2 Diabetes in Children and Adolescents Jill Jin, MD, MPH JAMA

Importance   Of youths diagnosed with type 2 diabetes, many develop microvascular complications by young adulthood.

Objective   To review the evidence on benefits and harms of screening children and adolescents for prediabetes and type 2 diabetes to inform the US Preventive Services Task Force (USPSTF).

Data Sources   PubMed/MEDLINE, Cochrane Library, and trial registries through May 3, 2021; references; experts; literature surveillance through July 22, 2022.

Study Selection   English-language controlled studies evaluating screening or interventions for prediabetes or type 2 diabetes that was screen detected or recently diagnosed.

Data Extraction and Synthesis   Dual review of abstracts, full-text articles, and study quality; qualitative synthesis of findings.

Main Outcomes and Measures   Mortality, cardiovascular morbidity, diabetes-related morbidity, development of diabetes, quality of life, and harms.

Results   This review included 8 publications (856 participants; mean age, 14 years [range, 10-17 years]). Of those, 6 were from the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) study. No eligible studies directly evaluated the benefits or harms of screening. One randomized clinical trial (RCT) (TODAY; n = 699 adolescents with obesity; mean age, 14 years) comparing metformin, metformin plus rosiglitazone, and metformin plus lifestyle intervention reported that 2 youths with recently diagnosed diabetes developed kidney impairment (0 vs 1 vs 1, respectively; P  > .99) and 11 developed diabetic ketoacidosis (5 vs 3 vs 3, respectively; P  = .70). One RCT of 75 adolescents (mean age, 13 years) with obesity with prediabetes compared an intensive lifestyle intervention with standard care and reported that no participants in either group developed diabetes, although follow-up was only 6 months. Regarding harms of interventions, 2 RCTs assessing different comparisons enrolled youths with recently diagnosed diabetes. Major hypoglycemic events were reported by less than 1% of participants. Minor hypoglycemic events were more common among youths treated with metformin plus rosiglitazone than among those treated with metformin or metformin plus lifestyle intervention in TODAY (8.2% vs 4.3% vs 3.4%, P  = .05). In 1 study, gastrointestinal adverse events were more commonly reported by those taking metformin than by those taking placebo (abdominal pain: 25% vs 12%; nausea/vomiting: 17% vs 10%; P not reported).

Conclusions and Relevance   No eligible studies directly evaluated the benefits or harms of screening for prediabetes and type 2 diabetes in children and adolescents. For youths with prediabetes or recently diagnosed (not screen-detected) diabetes, the only eligible trials reported few health outcomes and found no difference between groups, although evidence was limited by substantial imprecision and a duration of follow-up likely insufficient to assess health outcomes.

An estimated 210 000 US children and adolescents (2.5 per 1000) had diabetes in 2018, of whom approximately 23 000 had type 2 diabetes (0.24 per 1000). 1 Prevalence estimates for prediabetes from 2005 to 2016 indicated that almost 20% of those aged 12 to 18 years had prediabetes. 2 Data indicate that the prevalence and incidence of type 2 diabetes are increasing. 3 , 4 Risk factors include overweight and obesity, age (most pediatric cases occur after age 10 years, with the peak occurring at midpuberty), and family history. 5 Prevalence estimates are highest in American Indian/Alaska Native, Black, and Hispanic youth. 6 Differences in the frequencies of type 2 diabetes by socioeconomic position, area of residence, and environmental factors have also been described; the relative contributions of various factors to racial and ethnic differences are largely unknown, but structural factors that disproportionately affect racial and ethnic minority populations (eg, quality of and access to health care, toxic stress, structural racism) may contribute significantly. 7 , 8

The major acute complications of type 2 diabetes in youth are diabetic ketoacidosis and hyperglycemic hyperosmolar state. 9 Long-term morbidity is due to both macrovascular disease (atherosclerosis) and microvascular disease (retinopathy, nephropathy, and neuropathy). Among those with type 2 diabetes diagnosed during childhood and adolescence, many develop complications of kidney disease, retinopathy, and peripheral neuropathy during teenage years and young adulthood. 10 , 11

In 2021, the US Preventive Services Task Force (USPSTF) recommended screening for prediabetes and type 2 diabetes in adults aged 35 to 70 years with overweight or obesity (B recommendation). The USPSTF has not previously issued a recommendation on this topic for children and adolescents. This review evaluated the evidence on screening children and adolescents for prediabetes and type 2 diabetes for populations and settings relevant to primary care in the US to inform an updated recommendation by the USPSTF.

Detailed methods are available in the full evidence review. 5  Figure 1 shows the analytic framework, the key questions (KQs) that guided the systematic review, and the contextual questions intended to provide additional background information. In addition to addressing the KQs, this review looked for evidence related to 5 contextual questions that focused on progression from prediabetes to diabetes (natural history of prediabetes), whether screening or interventions change intermediate outcomes, agreement among screening tests, and risk assessment tools.

eTable 1 in the Supplement shows general categories and definitions of diabetes. 13 Three tests can be used to identify prediabetes and type 2 diabetes: hemoglobin A 1c (HbA 1c ) level, fasting plasma glucose level, or an oral glucose tolerance test (OGTT) (eTable 2 in the Supplement ).

PubMed/MEDLINE and the Cochrane Library were searched for English-language articles published through May 3, 2021. Search strategies are listed in the eMethods in the Supplement . Clinical trial registries were searched for unpublished studies. To supplement electronic searches, investigators reviewed reference lists of pertinent articles, studies suggested by reviewers, and comments received during public commenting periods. Since May 2021, ongoing surveillance was conducted through article alerts and targeted searches of journals to identify major studies published in the interim that may affect the conclusions or understanding of the evidence and the related USPSTF recommendation. The last surveillance was conducted on July 22, 2022.

Two investigators independently reviewed titles, abstracts, and full-text articles to determine eligibility using prespecified criteria (eTable 3 in the Supplement ). Disagreements were resolved by discussion and consensus. English-language studies of asymptomatic, nonpregnant persons younger than 18 years conducted in countries categorized as very high on the Human Development Index 14 and rated as fair or good quality were included. For all KQs, randomized clinical trials (RCTs) and nonrandomized controlled intervention studies were eligible. Controlled prospective cohort studies were also eligible for KQs on harms (KQ2 and KQ4) and the change in health outcomes after reduction in type 2 diabetes incidence (KQ6); case-control studies were eligible for KQs on harms (KQ2 and KQ4). For KQ1 and KQ2 (direct evidence of benefits and harms of screening), studies that compared screening with HbA 1c , fasting glucose, or OGTT with no screening or alternative screening strategies were eligible. For KQs 3 through 6 (benefits and harms of interventions), studies that evaluated primary care–relevant behavioral counseling interventions or pharmacologic interventions for glycemic control for prediabetes or diabetes were eligible.

For each included study, 1 investigator extracted pertinent information about the populations, tests or treatments, comparators, outcomes, settings, and designs, and a second investigator reviewed this information for completeness and accuracy. Two independent investigators assessed the quality of studies as good, fair, or poor, using predefined criteria (eTables 4-6 in the Supplement ) developed by the USPSTF and adapted for this topic. 12 Disagreements were resolved by discussion.

Findings for each KQ were summarized in tabular and narrative format. The overall strength of the evidence for each KQ was assessed as high, moderate, low, or insufficient based on the overall quality of the studies, consistency of results between studies, precision of findings, risk of reporting bias, and limitations of the body of evidence, using methods developed for the USPSTF (and the Evidence-based Practice Center program). 12 Additionally, the applicability of the findings to US primary care populations and settings was assessed. Discrepancies were resolved through consensus discussion.

The appropriateness of meta-analyses was determined using established guidance to assess the clinical and methodological heterogeneity of the studies. 15 The populations, tests, treatments, comparators, outcomes, and study designs were assessed qualitatively, looking for similarities and differences. Because of the limited number of similar studies for each KQ, meta-analyses were not conducted.

A total of 8 publications were included ( Figure 2 ). Individual study quality ratings are reported in eTables 4-6 in the Supplement . The 8 publications reported on 3 RCTs and included a total of 856 participants with a mean age of 14 years (range, 10-17 years).

Key Question 1. Is there direct evidence that screening for type 2 diabetes and prediabetes in asymptomatic children and adolescents improves health outcomes?

No eligible studies addressed this question.

Key Question 2. What are the harms of screening for type 2 diabetes and prediabetes in asymptomatic children and adolescents?

Key Question 3a. Do interventions for screen-detected type 2 diabetes and prediabetes provide an incremental benefit in health outcomes when delivered at the time of detection compared with initiating interventions later, after clinical diagnosis?

Key Question 3b. Do interventions for screen-detected type 2 diabetes and prediabetes improve health outcomes compared with no intervention, usual care, or interventions with different treatment targets?

Key Question 3c. Do interventions for recently diagnosed type 2 diabetes improve health outcomes compared with no intervention, usual care, or interventions with different treatment targets?

In summary, no eligible studies addressed KQ3a or KQ3b; 2 RCTs were eligible for KQ3c.

The review included 2 RCTs (described in 7 articles) ( Table 1 ). 16 - 22 One was rated as good quality and 1 was rated as fair quality. The 1 good-quality RCT (described in 6 articles), the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) study, enrolled 699 participants and evaluated interventions for recently diagnosed diabetes. 17 - 22 The TODAY study was a 15-site multicenter trial conducted in the US. The trial randomized adolescents with obesity (body mass index [BMI] ≥85th percentile for age and sex) and recently diagnosed diabetes to receive metformin monotherapy, metformin plus rosiglitazone, or metformin plus a lifestyle intervention. Prior to randomization, all participants completed a run-in of 2 to 6 months that involved weaning from nonstudy diabetes medications, initiating metformin at a dose of up to 1000 mg twice daily, attaining glycemic control with metformin alone (HbA 1c <8.0%), providing standard diabetes education and ensuring the participants’ mastery of the material, and confirming adherence. The mean age of participants was 14 years; mean BMI was 35 (calculated as weight in kilograms divided by height in meters squared); mean baseline HbA 1c values were 7.0% to 7.3% across the 3 study groups; 65.0% were female; 32.5% were non-Hispanic Black, 39.7% were Hispanic, and 20.3% were non-Hispanic White. The duration of follow-up ranged from 2 to 6.5 years (mean, 3.8 years). The lifestyle intervention focused on diet/nutrition, physical activity, and family support. The program included 3 phases of in-person contacts: once weekly for the first 6 to 8 months, twice weekly for months 6 to 8 through months 12 to 16, and then once monthly until the end of the study. The primary outcome of the trial was loss of glycemic control, defined as an HbA 1c level of at least 8% for 6 months or sustained metabolic decompensation requiring insulin, and the study focused largely on intermediate outcomes (eg, glycemic control, BMI) rather than on health outcomes.

The second trial 16 compared metformin and placebo in 82 treatment-naive adolescents aged 10 to 16 years with previous or newly diagnosed diabetes. 16 It was a 16-week double-blind placebo-controlled trial of 82 adolescents recruited from 44 sites in multiple countries, including the US, Russia, Belarus, Ukraine, and Poland. Most participants were from the US sites. The intervention group received up to 2000 mg daily of metformin for 16 weeks. The mean age of participants was 14 years; mean BMI was 34; mean baseline HbA 1c values were 8.3% to 9.0% across the study groups; 69.0% were female; and 37.0% were White. The primary outcome was change in fasting plasma glucose level from baseline.

The TODAY study reported 2 cases of kidney impairment, defined as an estimated creatinine clearance of less than 70 mL/min/1.73 m 2 (1.17 mL/s/m 2 ) or a serum creatinine level of more than 1.5 mg/dL (132.6 μmol/L) ( Table 2 ). One case was in the metformin plus rosiglitazone group, and 1 was in the metformin plus lifestyle intervention group ( P  > .99).

The TODAY study reported that 11 participants developed diabetic ketoacidosis. There was no statistically significant difference across treatment groups (5 [2.1%] for metformin monotherapy vs 3 [1.3%] for metformin plus rosiglitazone vs 3 [1.3%] for metformin plus lifestyle intervention, P  = .70). The smaller trial reported that 0 participants in the metformin group and 1 person in the control group developed diabetic ketoacidosis.

No eligible studies reported other health outcomes, including mortality, cardiovascular morbidity (including myocardial infarction, stroke, congestive heart failure), amputation, skin ulcers, visual impairment (including blindness), neuropathy, and quality of life.

Key Question 4. What are the harms of interventions for prediabetes, screen-detected type 2 diabetes, or recently diagnosed type 2 diabetes?

Overall, 2 RCTs (described in 7 articles) that enrolled a total of 781 youths (mean age, 14 years) with recently diagnosed type 2 diabetes were eligible. 16 - 22 The 2 trials assessed different comparisons. Major hypoglycemic events were reported by less than 1% of participants. Minor hypoglycemic events were more common among youths treated with metformin plus rosiglitazone than among those treated with metformin or metformin plus lifestyle intervention. In 1 study, gastrointestinal adverse events were more commonly reported by those taking metformin than by those taking placebo. Gastrointestinal adverse events, infections, and muscle aches and pains were less common among youths treated with metformin plus rosiglitazone than with metformin alone or metformin plus a lifestyle intervention. No eligible studies assessed harms for youths with screen-detected diabetes or prediabetes, and no eligible studies reported on harms of lifestyle interventions provided without pharmacotherapy.

Two RCTs (described in 7 articles) reported on harms of interventions for recently diagnosed type 2 diabetes ( Table 1 ). 16 - 22 The TODAY trial was described above in KQ3; it compared metformin monotherapy, metformin plus rosiglitazone, or metformin plus a lifestyle intervention. The second trial 16 was also described in KQ3; it reported on harms related to metformin (up to 2000 mg daily) compared with placebo in treatment-naive adolescents aged 10 to 16 years with previous or newly diagnosed type 2 diabetes. 16 The duration of follow-up ranged from 16 weeks 16 to a mean of 3.8 years (TODAY). Both studies reported on withdrawals, hypoglycemic events requiring medical attention, gastrointestinal adverse events, and lactic acidosis ( Table 3 ). The TODAY study reported on other adverse events, including rash, infection, sprain or fracture, muscle ache or pain, anemia, and edema. The TODAY study reported 0 deaths during the trial.

Serious hypoglycemic events requiring medical attention were reported in both trials and were rare ( Table 3 ). The TODAY study reported that 4 youths had severe hypoglycemia (1 [0.4%] for metformin monotherapy vs 1 [0.4%] for metformin plus rosiglitazone vs 2 [0.8%] for metformin plus lifestyle intervention, P  > .99). It also reported that more youths had repeated mild hypoglycemia in the group that received metformin plus rosiglitazone (10 [4.3%] for metformin monotherapy vs 19 [8.2%] for metformin plus rosiglitazone vs 8 [3.4%] for metformin plus lifestyle intervention, P  = .05). The 16-week trial 16 comparing metformin monotherapy with placebo reported 0 hypoglycemic events requiring medical attention in either study group.

Gastrointestinal adverse events were common in both studies. The TODAY study reported lower rates of gastrointestinal symptoms in the metformin plus rosiglitazone group (100 [42.9%]) than in the metformin monotherapy (129 [55.6%]) or metformin plus lifestyle intervention (136 [58.1%]) groups ( P  = .002). The 16-week trial 16 reported that more youths treated with metformin than with placebo had abdominal pain (25% vs 12%, P value not reported) and nausea or vomiting (17% vs 10%, P value not reported).

Both studies reported other adverse events; types of events reported (and definitions) varied, and most found no difference between groups or reported that no adverse events were attributed to study interventions ( Table 3 ). The TODAY study found higher rates of infection (64.2% vs 64.5% vs 51.5%, P  = .005) and muscle ache or pain (29.3% vs 32.9% vs 22.7%, P  = .05) in the metformin monotherapy and metformin plus lifestyle intervention groups than in the metformin plus rosiglitazone group. The TODAY study reported on rash, sprain or fracture, anemia, and edema but found no statistically significant differences between groups. The TODAY study reported that 1 participant in the metformin plus rosiglitazone group developed heart failure and 1 participant in the metformin monotherapy group developed lactic acidosis. The 16-week trial 16 reported that few participants had serious adverse events, all deemed unrelated to the study drug.

Key Question 5. Do interventions for prediabetes delay or prevent progression to type 2 diabetes?

The review included 1 fair-quality RCT (75 participants) that compared the Bright Bodies Healthy Lifestyle Program with standard care for adolescents with obesity (BMI >95th percentile) aged 10 to 16 years with prediabetes ( Table 1 ). 23 The trial was conducted in the US in a pediatric obesity clinic starting in September 2009. Regarding prediabetes ascertainment, the trial focused on impaired glucose tolerance for participant eligibility, defined as an elevated 2-hour OGTT (after a glucose load of 1.75 g/kg [maximum, 75 g]) result between 130 and 199 mg/dL (7.21-11.04 mmol/L) (using a range that was slightly wider than the current prediabetes criterion of 140 to 199 mg/dL [7.77-11.04 mmol/L]). The mean age of participants was 13 years, mean BMI was 33, mean baseline HbA 1c level was 5.6% to 5.7% across the groups, 64% were female, and 69% were White. The duration of follow-up was 6 months. The lifestyle program focused on both diet/nutrition and physical activity. The high-contact program included twice-weekly 50-minute exercise classes, a once-weekly weigh-in, and a 1-time 40-minute nutrition/behavior modification class (all administered in group settings). Participants were encouraged to exercise 3 additional days per week and record the duration and type of exercise. The study used raffle tickets for gift cards to motivate participants; tickets could be earned if weight stayed the same or decreased and, in some cases, if participants returned their weekly exercise log. The trial was rated as fair quality mainly because of the overall attrition (of 23%) and because some participants withdrew because they started metformin.

The primary outcome of the trial was the 6-month change in plasma glucose level 2 hours after OGTT (intermediate outcomes are described in the Contextual Questions [ Supplement ]). The trial reported that 0 participants developed diabetes during the trial.

Key Question 6. After interventions for prediabetes are provided, what is the magnitude of change in health outcomes that results from the reduction in type 2 diabetes incidence?

The details for the Contextual Questions are reported in the Supplement . In summary, Contextual Question 1 focuses on the natural history of prediabetes and found that 22% to 52% of children and adolescents with prediabetes returned to normal glycemia or normal glucose tolerance without intervention over 6 months to 2 years.

Contextual Questions 2 and 3 in the Supplement address whether interventions change intermediate outcomes for children and adolescents with screen-detected or recently diagnosed type 2 diabetes. In summary, Contextual Question 2 found that, among those recently diagnosed with type 2 diabetes, lifestyle and pharmacological interventions (metformin, rosiglitazone, liraglutide) improved glycemia, but data were limited or lacking about the effect of these interventions on other intermediate outcomes (microalbuminuria, subclinical retinopathy, subclinical neuropathy). Contextual Question 3 found that, for those with diabetes, metformin alone and metformin plus a lifestyle intervention were associated with decreases in BMI and weight when compared with metformin plus rosiglitazone in TODAY, 17 , 24 - 26 but another study reported that metformin was not associated with significant changes when compared with control. 16

Contextual Questions 2 and 3 in the Supplement also address whether interventions change intermediate outcomes for children and adolescents with prediabetes. In summary, Contextual Question 2 found that, among those with prediabetes, lifestyle interventions improved 2-hour glucose level (after OGTT), but not levels of fasting glucose or HbA 1c , in 1 trial, and data on rosiglitazone were inconclusive because of early trial discontinuation. Contextual Question 3 found that lifestyle interventions for children and adolescents with prediabetes improved weight and BMI compared with controls in 1 study 23 and that prediabetes identification was associated with decreases in BMI in adolescents with obesity and overweight, although evidence was from a retrospective cohort study with many limitations and a medium to high risk of bias. 27

Contextual Question 4 in the Supplement summarizes studies reporting on the frequency of agreement among screening tests (eTable 7 in the Supplement ). Contextual Question 5 in the Supplement describes 2 risk assessment tools for predicting risk of type 2 diabetes or prediabetes that have been validated in US children or adolescents: 1 using an automated computer system based on American Diabetes Association guidelines and 1 that adapted the Tool for Assessing Glucose Impairment (TAG-IT) adult risk assessment tool for pediatrics.

This study reviewed the evidence on benefits and harms of screening for prediabetes and type 2 prediabetes in children and adolescents. Table 4 provides a summary of the main findings in this evidence review organized by KQ, along with a description of consistency, precision, quality, limitations, strength of evidence, and applicability. Overall, limited data were eligible for this review, and the strength of evidence was graded as insufficient or low for all KQs. No eligible studies directly addressed the overarching question (ie, no studies evaluated screening for prediabetes or type 2 diabetes among asymptomatic youths compared with no screening or alternative screening strategies), and none enrolled children and adolescents with screen-detected diabetes.

For youths with recently diagnosed diabetes, the strength of evidence was graded as insufficient because of unknown consistency, substantial imprecision, and a duration of follow-up likely insufficient to assess health outcomes. For youths with prediabetes, this review found 1 eligible trial that assessed whether lifestyle interventions for prediabetes can help prevent progression to type 2 diabetes. However, the strength of evidence was graded as insufficient because follow-up was only 6 months, results were imprecise (with 0 events in either group), consistency is unknown (single study), and the study had high attrition. Among adults with obesity and overweight, recent meta-analyses for the USPSTF found high strength of evidence that lifestyle interventions were associated with reduction in the incidence of diabetes in trials with follow-up ranging from less than 1 year to 30 years (pooled relative risk, 0.78 [95% CI, 0.69-0.88]; 23 trials, 12 915 participants). 28

For harms of interventions for prediabetes or type 2 diabetes, low strength of evidence from the 2 included trials indicates that minor hypoglycemic events were more common among youths treated with metformin plus rosiglitazone than among those treated with metformin or metformin plus lifestyle intervention; gastrointestinal adverse effects were commonly associated with metformin; and gastrointestinal adverse events, infections, and muscle aches and pains were more common among youths treated with metformin or metformin plus a lifestyle intervention than with metformin plus rosiglitazone. The strength of evidence was downgraded to low because of imprecision and unknown consistency (studies assessed different comparisons), and 1 study was rated as having medium risk of bias.

This review has several limitations. First, non–English-language articles were excluded. Second, the review was limited to asymptomatic children and focused on the overarching question of screening for prediabetes or type 2 diabetes. It did not evaluate diagnostic testing of symptomatic children or those with signs of insulin resistance, diagnostic testing of children with conditions associated with insulin resistance, or screening for type 1 diabetes. Third, the review excluded studies limited to or predominately comprising adults or pregnant women and children and adolescents with symptomatic diabetes (eg, weight loss, polyuria, blurred vision, headache). In addition, studies of children and adolescents who had diabetes for more than 1 year or with more advanced diabetes were excluded, aiming to identify the studies with good applicability to a screen-detected population. Fourth, the review did not evaluate accuracy of screening tests because there is not a reference standard available for comparison; instead, studies reporting on the frequency of agreement among screening tests were evaluated in Contextual Question 4.

No eligible studies directly evaluated the benefits or harms of screening for prediabetes and type 2 diabetes in children and adolescents. For youths with prediabetes or recently diagnosed (not screen-detected) diabetes, the only eligible trials reported few health outcomes and found no difference between groups, although evidence was limited by substantial imprecision and a duration of follow-up likely insufficient to assess health outcomes.

Corresponding Author: Daniel E. Jonas, MD, MPH, Division of General Internal Medicine, Department of Internal Medicine, The Ohio State University, 2050 Kenny Rd, Columbus, OH 43221 ( [email protected] ).

Accepted for Publication: April 26, 2022.

Author Contributions: Dr Jonas had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Jonas, Vander Schaaf, Allison, LeBlanc.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: All authors.

Critical revision of the manuscript for important intellectual content: Jonas, Vander Schaaf, Allison, Ali, LeBlanc.

Statistical analysis: Jonas.

Obtained funding: Jonas.

Administrative, technical, or material support: Jonas, Riley, Middleton, Baker, Voisin.

Supervision: Jonas.

Conflict of Interest Disclosures: Dr Vander Schaaf reported receiving grants from The Duke Endowment to support collaboration to address food insecurity and participating on national committees of the American Academy of Pediatrics, which has position statements on pediatric screening. Dr LeBlanc reported that Dexcom donated continuous glucose monitoring devices for a multicenter National Institutes of Health study on which she is an investigator. No other disclosures were reported.

Funding/Support: This research was funded under contract HHSA290201500007I, Task Order 9, from the Agency for Healthcare Research and Quality (AHRQ), US Department of Health and Human Services, under a contract to support the USPSTF.

Role of the Funder/Sponsor: Investigators worked with USPSTF members and AHRQ staff to develop the scope, analytic framework, and key questions for this review. AHRQ had no role in study selection, quality assessment, or synthesis. AHRQ staff provided project oversight, reviewed the evidence review to ensure that the analysis met methodological standards, and distributed the draft for public comment and review by federal partners. Otherwise, AHRQ had no role in the conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript findings. The opinions expressed in this document are those of the authors and do not reflect the official position of AHRQ or the US Department of Health and Human Services.

Additional Contributions: We gratefully acknowledge the following individuals for their contributions to this project, including AHRQ staff (Justin Mills, MD, MPH, and Tracy Wolff, MD, MPH) and RTI International—University of North Carolina–Chapel Hill Evidence-based Practice Center staff (Carol Woodell, BSPH, Sharon Barrell, MA, and Loraine Monroe). The USPSTF members, peer reviewers, and federal partner reviewers did not receive financial compensation for their contributions. Ms Woodell, Ms Barrell, and Ms Monroe received compensation for their role in this project.

Additional Information: A draft version of the full evidence review underwent external peer review from 3 content experts (Callie L. Brown, MD, MPH, Wake Forest University School of Medicine; Sheela N. Magge, MD, MSCE, Johns Hopkins University School of Medicine; Hanna Xu, MD, Cook County Health, Illinois) and 3 federal partner reviewers (Centers for Disease Control and Prevention, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institute of Diabetes and Digestive and Kidney Diseases). Comments from reviewers were presented to the USPSTF during its deliberation of the evidence and were considered in preparing the final evidence review. USPSTF members and peer reviewers did not receive financial compensation for their contributions.

Editorial Disclaimer: This evidence review is presented as a document in support of the accompanying USPSTF Recommendation Statement. It did not undergo additional peer review after submission to JAMA .

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• Published: 30 May 2024

Barriers and facilitators to mental health treatment access and engagement for LGBTQA+ people with psychosis: a scoping review protocol

• Cláudia C. Gonçalves   ORCID: orcid.org/0000-0001-6767-0920 1 ,
• Zoe Waters 2 ,
• Shae E. Quirk 1 ,
• Peter M. Haddad 1 , 3 ,
• Ashleigh Lin 4 ,
• Lana J. Williams 1 &
• Alison R. Yung 1 , 5  

Systematic Reviews volume  13 , Article number:  143 ( 2024 ) Cite this article

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The prevalence of psychosis has been shown to be disproportionately high amongst sexual and gender minority individuals. However, there is currently little consideration of the unique needs of this population in mental health treatment, with LGBTQA+ individuals facing barriers in accessing timely and non-stigmatising support for psychotic experiences. This issue deserves attention as delays to help-seeking and poor engagement with treatment predict worsened clinical and functional outcomes for people with psychosis. The present protocol describes the methodology for a scoping review which will aim to identify barriers and facilitators faced by LGBTQA+ individuals across the psychosis spectrum in help-seeking and accessing mental health support.

A comprehensive search strategy will be used to search Medline, PsycINFO, Embase, Scopus, LGBTQ+ Source, and grey literature. Original studies of any design, setting, and publication date will be included if they discuss barriers and facilitators to mental health treatment access and engagement for LGBTQA+ people with experiences of psychosis. Two reviewers will independently screen titles/abstracts and full-text articles for inclusion in the review. Both reviewers will then extract the relevant data according to pre-determined criteria, and study quality will be assessed using the Joanna Briggs Institute (JBI) critical appraisal checklists. Key data from included studies will be synthesised in narrative form according to the Guidance on the Conduct of Narrative Synthesis in Systematic Reviews.

The results of this review will provide a comprehensive account of the current and historical barriers and facilitators to mental healthcare faced by LGBTQA+ people with psychotic symptoms and experiences. It is anticipated that the findings from this review will be relevant to clinical and community services and inform future research. Findings will be disseminated through publication in a peer-reviewed journal and presented at conferences.

Scoping review registration

This protocol is registered in Open Science Framework Registries ( https://doi.org/10.17605/OSF.IO/AT6FC ).

Peer Review reports

The prevalence of psychotic disorders in the general population has been estimated to be around 0.27–0.75% [ 1 , 2 ], with the lifetime prevalence of ever having a psychotic experience being estimated at 5.8% [ 3 ]. However, rates of psychotic symptoms and experiences are disproportionately high amongst LGBTQA+ populations, with non-heterosexual individuals estimated to be 1.99–3.75 times more likely to experience psychosis than their heterosexual peers [ 4 , 5 , 6 , 7 ]. Additionally, it has been estimated that transgender or gender non-conforming (henceforth trans) individuals are 2.46–49.7 times more likely than their cisgender peers (i.e. individuals whose gender identity is the same as their birth registered sex) to receive a psychotic disorder diagnosis [ 8 , 9 ]. The increased rates of psychotic experiences noted amongst gender and sexual minorities may be explained by evidence indicating that LGBTQA+ people are also exposed to risk factors for psychosis at a far greater rate than members of the general population, such as childhood adversity [ 10 , 11 , 12 ], minority stress [ 13 ], discrimination [ 14 ], and stigma [ 15 , 16 ]. Furthermore, there is added potential for diagnostic biases leading to over-diagnosing psychosis in gender diverse individuals, whose gender expression and dysphoria may be pathologized by mental health service providers [ 8 ].

Despite these concerning statistics, there is very little research examining the experiences of LGBTQA+ people with psychosis, and limited consideration of the unique needs these individuals may have in accessing and engaging with mental health services. While timely access to treatment has consistently been associated with better symptomatic and functional outcomes for people with psychosis [ 17 , 18 ], there are often delays to treatment initiation which are worsened for LGBTQA+ individuals [ 19 , 20 ]. These individuals face additional barriers to accessing adequate mental health support compared to cisgender/heterosexual people [ 19 ] and may need to experiment with several mental health services before finding culturally competent care [ 20 ]. This in turn may lead to longer duration of untreated psychosis. Additionally, there seems to be a lack of targeted support for this population from healthcare providers, with LGBTQA+ individuals with serious mental health concerns reporting higher rates of dissatisfaction with psychiatric services than their cisgender and heterosexual counterparts [ 7 , 14 , 21 ]. However, the extent of these differences varies across contexts [ 22 ], potentially due to improved education around stigma and LGBTQA+ issues within a subset of mental health services.

Nonetheless, stigma remains one of the highest cited barriers to help-seeking for mental health problems, particularly with regard to concerns around disclosure [ 23 ], which can be particularly challenging for people experiencing psychosis [ 24 , 25 ]. Stigma stress in young people at risk for psychosis is associated with less positive attitudes towards help-seeking regarding both psychiatric medication and psychotherapy [ 26 ], potentially partly due to fears of judgement and being treated differently by service providers [ 27 ]. This issue may be compounded for people who also belong to minoritized groups [ 23 , 28 ], particularly as LGBTQA+ individuals have reported experiencing frequent stigma and encountering uninformed staff when accessing mental healthcare [ 7 , 29 ]. Furthermore, stigma-fuelled hesitance to access services may be heightened for trans people [ 30 ] whose identities have historically been pathologized and conflated with experiences of psychosis [ 31 ].

Even when individuals manage to overcome barriers to access support, there are added challenges to maintaining adequate treatment engagement. In a large online study, half of trans and nearly one third of LGB participants reported having stopped using mental health services in the past because of negative experiences related to their gender identity or sexuality [ 20 ]. This can be particularly problematic as experiences of stigma predict poorer medication adherence in psychosis [ 32 ] which subsequently multiplies the risk for relapse and suicide [ 33 ]. While no research to date has explored non-adherence rates in people with psychosis who are LGBTQA+, concerns around suicidality are heightened for individuals who are gender and sexuality diverse [ 34 , 35 , 36 ].

Generally, there is rising demand for mental healthcare that specifically addresses the needs of gender and sexual minority individuals and promotes respect for diversity, equity, and inclusion [ 29 , 37 ]. This is particularly salient as positive relationships with staff are associated with better medication adherence for people with psychosis [ 38 ] and healthcare providers with LGBTQA+-specific mandates have demonstrated higher satisfaction rates for LGBTQA+ individuals [ 20 ]. Mental health services need to adapt treatment options to acknowledge minority stress factors for those with stigmatised identities and, perhaps more importantly, how these intersect and interact to increase inequalities in people from minoritized groups accessing and benefiting from treatment [ 37 , 39 ].

Additionally, gender affirming care needs to be recognised as an important facet of mental health treatment for many trans individuals, as it is associated with positive outcomes such as improvements in quality of life and psychological functioning [ 40 , 41 , 42 ] and reductions in psychiatric symptom severity and need for subsequent mental health treatment [ 8 , 43 ]. While there are additional barriers in access to gender affirming care for individuals with psychosis, this treatment has shown success in parallel with treatment to address psychosis symptom stabilisation [ 19 , 44 ]. The importance of affirmation is echoed by the finding that many negative experiences of LGBTQA+ participants with mental health services could be avoided simply by respecting people’s pronouns and using gender-neutral language [ 20 ].

To ensure timely access to appropriate treatment for LGBTQA+ people with psychosis, there is a need for improved understanding of the factors which challenge and facilitate help-seeking and engagement with mental health support. A preliminary search of Google Scholar, Medline, the Cochrane Database of Systematic Reviews, and PROSPERO was conducted and revealed no existing or planned reviews exploring benefits and/or obstacles to mental health treatment specific to this population. Therefore, the proposed review seeks to comprehensively search and appraise the existing literature to identify and summarise a range of barriers and facilitators to adequate mental health support faced by LGBTQA+ people with experiences of psychosis. This will allow for the mapping of the types of evidence available and identification of any knowledge gaps. Moreover, we hope to guide future decision-making in mental healthcare to improve service accessibility for LGBTQA+ individuals with psychosis and to set the foundations for future research that centres this marginalised population. Based on published guidance [ 45 , 46 , 47 ], a scoping review methodology was identified as the most appropriate approach to address these aims.

Selection criteria

This scoping review protocol has been developed in compliance with the JBI Manual for Evidence Synthesis [ 48 ] and, where relevant, the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) checklist [ 49 ] (see Additional file 1). In the event of protocol amendments, the date, justification, and description for each amendment will be provided.

Due to the limited literature around the topic of this review, any primary original study design, setting, and publication date will be considered for inclusion. Publications written in English will be included, and articles in other languages may be considered pending time and cost constraints around translation. Publications will be excluded if the full text is not available upon request from authors.

The PCC (Population, Concept, Context) framework was used to develop the inclusion criteria for this scoping review:

This review will include individuals of any age who are LGBTQA+ and have had experiences of psychosis. For the purposes of this review, ‘LGBTQA+ individuals’ will be broadly defined as any individual that is not heterosexual and/or cisgender or anyone who engages in same-gender sexual behaviour. Studies may include participants who are cisgender and heterosexual if they separately report outcomes for LGBTQA+ individuals. Within this review, the term ‘psychosis’ includes (i) any diagnosis of a psychotic disorder, such as schizophrenia spectrum disorders, mood disorders with psychotic features, delusional disorders, and drug-induced psychotic disorders, (ii) sub-threshold psychotic symptoms, such as those present in ultra-high risk (UHR), clinical high risk (CHR), or at risk mental state (ARMS) individuals, and (iii) any psychotic-like symptoms or experiences. Studies may include participants with multiple diagnoses if they separately report outcomes for individuals on the psychosis spectrum.

This review will include publications which discuss potential barriers and/or facilitators to mental health help-seeking and/or engagement with mental health treatment. ‘Barriers’ will be operationalised as any factors which may delay or prevent individuals from accessing and engaging with appropriate mental health support. These may include lack of mental health education, experienced or internalised stigma, experiences of discrimination from health services, and lack of inclusivity in health services. ‘Facilitators’ will be operationalised as any factors which may promote timely help-seeking and engagement with sources of support. These may include improved access to mental health education, positive sources of social support, and welcoming and inclusive services. Mental health help-seeking will be broadly defined as any attempt to seek and access formal or informal support to address a mental health concern related to experiences of psychosis (e.g. making an initial appointment with a service provider, seeking help from a friend). Mental health treatment engagement will be broadly defined as adherence and active participation in the treatment that is offered by a source of support (e.g. attending scheduled appointments, taking medication as prescribed, openly communicating with service providers).

This review may include research encompassing any setting in which mental healthcare is provided. This is likely to include formal healthcare settings such as community mental health teams or inpatient clinics as well as informal settings such as LGBTQA+ spaces or informal peer support. Studies will be excluded if they focus exclusively on physical health treatment.

Search strategy

Database searches will be conducted in Medline, PsycINFO, Embase, Scopus, and LGBTQ+ Source. The full search strategy for this protocol is available (see Additional file 2). This strategy has been collaboratively developed and evaluated by a scholarly services health librarian. Searches will include subject headings relevant to each database and title/abstract keywords relating to three main concepts: (i) LGBTQA+ identity, (ii) experiences of psychosis, and (iii) mental health treatment. Keywords for each concept will be combined using the Boolean operator ‘OR’, and the three concepts will be combined using ‘AND’. This search strategy was appropriately translated for each of the selected databases. There will be no limitations on language or publication date at this stage to maximise the breadth of the literature captured. Publications returned from these searches will be exported to EndNote. Searches will be re-run prior to the final analysis to capture any newly published studies.

The database searches will be supplemented by searching the grey literature as per the eligibility criteria detailed above. These may include theses and dissertations, conference proceedings, reports from mental health services, and policy documents from LGBTQA+ groups. Google and Google Scholar will be searched using a combination of clauses for psychosis (Psychosis OR psychotic OR schizophrenia OR schizoaffective), treatment (treatment or “help-seeking”), and queer identity. The latter concept will have three clauses for three separate searches, with one including broad queer identity (LGBT), one specific to non-heterosexual individuals (gay OR lesbian OR homosexual OR bisexual OR queer OR asexual), and one specific to trans individuals (transgender OR transsexual OR transexual OR “non-binary” OR “gender minority”). Additionally, reference lists and citing literature will be manually searched for each paper included in the review to capture any articles and policy documents not previously identified.

Data selection

Search results will be imported into Covidence using EndNote, and duplicates will be eliminated. Titles and abstracts will be screened by the first and second authors according to pre-defined screening criteria, which will be discussed by the authors and piloted prior to screening. These criteria will consider whether the articles included LGBTQA+ participants with experiences of psychosis (as operationalised above) in relation to mental health help-seeking and/or treatment. Full texts of relevant articles will then be obtained and screened by the first and second reviewer in accordance with the full inclusion and exclusion criteria after initial piloting to maximise inter-rater reliability. Decisions on inclusion and exclusion will be blinded and recorded on Covidence. Potential discrepancies will be resolved through discussion, and when consensus cannot be reached, these will be resolved by the supervising author. The process of study selection will be documented using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram [ 50 ].

Data extraction

Data extraction will be performed independently by two reviewers using Covidence. Prior to beginning final extraction, both reviewers will independently pilot the extraction tool using a sample of five included studies and discuss any necessary changes. Information extracted is planned to include the following: title, author name(s), year of publication, country in which the study was conducted, study design, sample size, population of focus (i.e. sexual minorities, gender minorities, or both), sample demographics (i.e. age, gender identity, and sexual orientation), setting (e.g. early intervention service, community mental health team, etc.), psychosis characteristics (e.g. diagnoses included, severity of symptoms, etc.), type of treatment (e.g. cognitive behavioural therapy, antipsychotic medication, etc.), and any barriers and/or facilitators identified according to the aforementioned operationalised definitions. Disagreements will be resolved through discussion between the two reviewers and, when necessary, final decisions will be made by a senior supervisor. Once extracted, information will be recorded in Excel. Lead authors of papers will be contacted by the primary review author in cases where there is missing or insufficient data.

Quality assessment

Due to the expected heterogeneity in the types of studies that may be included in this review (e.g. qualitative studies, randomised controlled trials, case control studies, case reports), the relevant revised Joanna Briggs Institute (JBI) critical appraisal checklists [ 51 ] will be used to assess risk of bias and study quality for each study design. Two reviewers will independently use these checklists to assess each paper that is included following the full-text screening. If there are discrepancies in article ratings, these will be resolved through discussion between the two authors. If no consensus is reached, discrepancies will be resolved by a senior supervisor. In line with the scoping nature of this review, low-quality studies will not be excluded from the synthesis.

Evidence synthesis

Data from included studies will be synthesised using a narrative synthesis approach in accordance with the Guidance on the Conduct of Narrative Synthesis in Systematic Reviews [ 52 ]. A preliminary descriptive synthesis will be conducted by tabulating the extracted data elements from each study alongside quality assessment results and developing an initial description of the barriers and facilitators to (1) accessing and (2) engaging with mental health support that are identified in the literature. This initial synthesis will then be interrogated and refined to contextualise these barriers and facilitators in the setting, population, and methodology of each study to form the basis for an interpretative synthesis.

This review will not use a pre-existing thematic framework to categorise barriers and facilitators as it is expected that the factors identified will not neatly fit into existing criteria. Instead, these will be conceptualised according to overarching themes as interrelated factors, so that potentially complex interactions between barriers and facilitators within and across relevant studies may be explored through concept mapping. If most of the studies included are qualitative, there may also be scope for a partial meta-synthesis. To avoid oversimplifying the concept of ‘barriers and facilitators’ (see criticism by Bach-Mortensen & Verboom [ 53 ]), this data synthesis will be followed by a critical reflection of the findings through the lens of the socio-political contexts which may give rise to the barriers and facilitators identified, exploring the complexities necessary for any changes to be implemented in mental health services.

If the extracted data indicate that gender minority and sexual minority individuals experience unique or different barriers and/or facilitators to each other, these population groups will be analysed separately as opposed to findings being generalised across the LGBTQA+ spectrum. Furthermore, if there is scope to do so, analyses may be conducted to investigate how perceived barriers and facilitators for this population may have changed over time (i.e. according to publication date) as definitions of psychosis evolve and LGBTQA+ individuals gain visibility in clinical services.

The proposed review will add to the literature around mental health treatment for LGBTQA+ people with psychosis. It will provide a thorough account of the barriers and facilitators to accessing and engaging with support faced by this population and may inform future research and clinical practice.

In terms of limitations, this review will be constrained by the existing literature and may therefore not be sufficiently comprehensive in reflecting the barriers and facilitators experienced by subgroups within the broader LGBTQA+ community. Additionally, although broad inclusion criteria are necessary to capture the full breadth of research conducted in this topic, included studies are likely to be heterogeneous and varied in terms of their methodology and population which may complicate data synthesis.

Nonetheless, it is anticipated that the findings from this review will provide the most comprehensive synthesis to date of the issues driving low help-seeking and treatment engagement in people across the psychosis spectrum who are LGBTQA+. This review will likely also identify gaps in the literature which may inform avenues for future research, and the factors identified in this review will be considered in subsequent research by the authors.

Additionally, findings will be relevant to healthcare providers that offer support to people with psychosis who may have intersecting LGBTQA+ identities as well as LGBTQA+ organisations which offer support to LGBTQA+ people who may be experiencing distressing psychotic experiences. These services are likely to benefit from an increased awareness of the factors which may improve or hinder accessibility for these subsets of their target populations. Therefore, results from this review may inform decision-making around the implementation of service-wide policy changes.

The findings of this review will be disseminated through the publication of an article in a peer-reviewed journal and presented at relevant conferences in Australia and/or internationally. Additionally, the completed review will form part of the lead author’s doctoral thesis.

Availability of data and materials

Not applicable for this protocol.

Abbreviations

• At risk mental state

Clinical high risk for psychosis

Joanna Briggs Institute

Lesbian, gay, and bisexual

Lesbian, gay, bisexual, transgender, queer or questioning, asexual or aromantic, and more

Population, Concept, Context

Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols

Ultra-high risk for psychosis

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Acknowledgements

The authors would like to acknowledge the support of Ms Olivia Larobina, Scholarly Services Librarian (STEMM) at Deakin University, in the development of the search strategy.

CCG is funded by a Deakin University Postgraduate Research (DUPR) Scholarship. ZW is funded by a University of Western Australia Research Training Program (RTP) Scholarship. AL is supported by a National Health and Medical Research Council (NHMRC) Emerging Leaders Fellowship (2010063). LJW is supported by a NHMRC Emerging Leaders Fellowship (1174060). ARY is supported by a NHMRC Principal Research Fellowship (1136829). The funding providers had no role in the design and conduct of the study, or in the preparation, review, or approval of this manuscript.

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Cláudia C. Gonçalves, Shae E. Quirk, Peter M. Haddad, Lana J. Williams & Alison R. Yung

Telethon Kids Institute, University of Western Australia, Perth, WA, 6009, Australia

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CCG is the guarantor. CCG conceptualised the review, developed the study design, and drafted the manuscript. CCG, ZW, and SQ collaborated with OL (Scholarly Services Librarian) to develop the search strategy. All authors critically reviewed the manuscript. All authors read and approved the final manuscript.

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Correspondence to Cláudia C. Gonçalves .

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In the last 3 years, PMH has received honoraria for lecturing from Janssen, NewBridge Pharmaceuticals, and Otsuka and royalties from edited textbooks (Cambridge University Press, Oxford University Press).

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Supplementary Information

Additional file 1. prisma-p 2015 checklist. completed prisma-p checklist for this systematic review protocol., 13643_2024_2566_moesm2_esm.docx.

Additional file 2. Search Strategy. Detailed search strategy for this systematic review, including search terms and relevant controlled vocabulary terms for each included database.

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Gonçalves, C.C., Waters, Z., Quirk, S.E. et al. Barriers and facilitators to mental health treatment access and engagement for LGBTQA+ people with psychosis: a scoping review protocol. Syst Rev 13 , 143 (2024). https://doi.org/10.1186/s13643-024-02566-5

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• Assessing health outcomes: a systematic review of electronic patient-reported outcomes in oncology
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• http://orcid.org/0000-0003-1880-5731 Mikel Urretavizcaya 1 ,
• Karen Álvarez 2 ,
• Olatz Olariaga 1 ,
• Maria Jose Tames 1 ,
• Ainhoa Asensio 1 ,
• Gerardo Cajaraville 1 ,
• http://orcid.org/0000-0002-8986-0247 Ana Cristina Riestra 1 , 3
• 1 Pharmacy Department , Onkologikoa , San Sebastian , País Vasco , Spain
• 2 Pharmacy Department , Nuestra Senora de la Candelaria University Hospital , Santa Cruz de Tenerife , Canarias , Spain
• 3 Medicine Department , University of Deusto , Bilbao , País Vasco , Spain
• Correspondence to Mikel Urretavizcaya, Pharmacy Department, Onkologikoa, San Sebastian, País Vasco, Spain; urretabizkaia.mikel{at}gmail.com

Purpose This study investigates the clinical impact of electronic patient-reported outcome (ePRO) monitoring apps/web interfaces, aimed at symptom-management, in cancer patients undergoing outpatient systemic antineoplastic treatment. Additionally, it explores the advantages offered by these applications, including their functionalities and healthcare team-initiated follow-up programmes.

Methods A systematic literature review was conducted using a predefined search strategy in MEDLINE. Inclusion criteria encompassed primary studies assessing symptom burden through at-home ePRO surveys in adult cancer patients receiving outpatient systemic antineoplastic treatment, whenever health outcomes were evaluated. Exclusion criteria excluded telemedicine-based interventions other than ePRO questionnaires and non-primary articles or study protocols. To evaluate the potential bias in the included studies, an exhaustive quality assessment was conducted, as an additional inclusion filter.

Results Among 246 identified articles, 227 were excluded for non-compliance with inclusion/exclusion criteria. Of the remaining 19 articles, only eight met the rigorous validity assessment and were included for detailed examination and data extraction, presented in attached tables.

Conclusion This review provides compelling evidence of ePRO monitoring’s positive clinical impact across diverse cancer settings, encompassing various cancer types, including early and metastatic stages. These systems are crucial in enabling timely interventions and reducing communication barriers, among other functionalities. While areas for future ePRO innovation are identified, the primary limitation lies in comparing clinical outcomes of reviewed articles, due to scale variability and study population heterogeneity. To conclude, our results reaffirm the transformative potential of ePRO apps in oncology and their pivotal role in shaping the future of cancer care.

• Patient Reported Outcomes
• Adverse Drug Reaction Reporting Systems
• Antineoplastic agents
• MEDICAL ONCOLOGY
• Quality of Life
• Outcome Assessment, Health Care

Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information. As this study is a systematic review, no new data were generated or analysed. All data used in this review are publicly available in the cited sources, and the comprehensive list of references is provided in the manuscript. The authors confirm that they had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

https://doi.org/10.1136/ejhpharm-2023-004072

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WHAT IS ALREADY KNOWN ON THIS TOPIC

Previous studies acknowledge that ePRO monitoring holds promise for timely symptom care and improved health-related quality of life (HRQL) in cancer treatment. However, its widespread adoption remains limited.

WHAT THIS STUDY ADDS

Our review offers compelling evidence supporting the increasingly apparent clinical benefits of ePRO monitoring, including reduced symptom burden, enhanced HRQL and even overall survival benefits. Additionally, we introduce a comprehensive checklist for evaluating diverse ePRO app functionalities, identifying areas for improvement and emphasising opportunities for innovation.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

This review highlights the transformative potential of ePRO apps in oncology, entailing a step forward in implementing ePRO monitoring in clinical practice.

Introduction

Symptoms experienced by cancer patients are a common and complex facet of their journey, stemming from various sources, including the cancer itself, treatment-related side effects, and coexisting conditions. 1 Alarmingly, these symptoms often evade detection by healthcare professionals in up to half of the cases. 2 Managing symptoms presents a significant challenge to the well-being and treatment outcomes of cancer patients. Uncontrolled symptoms can result in impaired health-related quality of life (HRQL), treatment adherence issues, chemotherapy delays or dose reductions, and distressing visits to emergency departments, ultimately affecting health outcomes and even mortality. 3–6

Traditionally, the reporting of symptoms has relied on patients' retrospective recall and self-identification of severe symptoms, leading to uncertainties and delayed reporting, and often, the inability to access timely care. 6 7 This delay places patients' safety at risk and necessitates the exploration of alternative approaches.

One promising avenue is the integration of electronic systems that facilitate patient-reported outcome (PRO) surveys, enabling early symptom detection and timely clinician intervention. 8 The systematic collection of symptom information through standardised PRO questionnaires has shown potential in improving symptom control. 9 10 Numerous web-based systems exist 11 12 and have demonstrated their ability to prompt clinicians to intensify symptom management, 13 14 enhance patient-clinician communication, and improve patient satisfaction and well-being. 15–21

Despite the compelling evidence supporting the benefits of electronic symptom monitoring through PROs, its widespread adoption in cancer treatment has been limited. 8 The hesitance to adopt these systems may stem from the ongoing debate regarding whether the clinical benefits of integrating electronic patient-reported outcomes (ePRO) into routine oncology practice outweigh the associated costs and burdens. 12 15 16 This integration demands technological resources, patient engagement, staff effort, and a reconfiguration of information flow. 22

In this context, the future of ePRO monitoring depends on evidence that it actually produces clinical benefits. To gain a clearer understanding of its value, it is imperative to identify which components of web-based support systems are most beneficial for patients. Unfortunately, this attempt is complicated by the fact that it remains unclear which specific eHealth functions are responsible for the reported clinical benefits. 23 This introduces an additional layer of complexity when comparing the health results obtained from different articles that use various apps, because, as the intervention (the components of web-based support systems) varies, it is to be expected that the obtained clinical benefits do too.

In light of these challenges and opportunities, this review explores the potential of electronic PRO systems to revolutionise the management of cancer-related symptoms, with a particular focus on their impact on health outcomes in the broadest sense. We also examine the functionalities and advantages offered by each PRO monitoring app and web interface, aiming to provide insights to the components included by web-based support systems that have demonstrated actual health benefits. Through an in-depth analysis of the existing literature, we seek to shed light on the role of electronic PRO systems in shaping the future of symptom management in cancer care.

We conducted a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines to ensure methodological quality.

Research questions

The PICO (Population, Intervention, Comparison and Outcome) model was employed to frame our clinical research questions. The following were proposed:

RQ1. Have ePRO monitoring apps/web interfaces, aimed at symptom assessment, demonstrated positive health results when applied to adult cancer outpatients receiving systemic antineoplastic agents?

RQ2. What kind of advantages do these applications offer to patients, both through their functionalities and through the follow-up programmes that the healthcare team offers?

Search strategy

The search was conducted in March 2023. The MEDLINE Public Library of Medicine (PubMed) database was explored for relevant studies using the following search terms, limited to the period from 2010 to present:

‘Patient Reported Outcome Measures’ OR ‘Patient Outcome Assessment’ OR ‘Healthcare Surveys’

‘Mobile Applications’ OR ‘Telemedicine’ OR ‘Tablet’

‘Neoplasms’

‘Drug-Related Side Effects and Adverse Reactions’ OR ‘Quality of Life’ OR ‘Self Care’ OR ‘Patient Satisfaction’

All search terms were combined using the Boolean operator ‘AND,’ resulting in the following search expression: A AND B AND C AND D.

The search was replicated in May 2024 to update the results in case of finding relevant articles.

Inclusion and exclusion criteria

Titles and abstracts were independently reviewed by two researchers to ensure eligibility to the predefined criteria. In case of disagreement, a third author reviewed to confirm inclusion or exclusion.

Studies meeting the following criteria were included: (i) primary studies assessing symptom burden, at least weekly, through at-home ePRO questionnaires; (ii) developed with adult cancer outpatients receiving systemic antineoplastic treatment; and (iii) whenever health outcomes were evaluated. The exclusion criteria were: (i) studies with telemedicine-based interventions other than the use of electronic questionnaires for the PRO registration; and (ii) articles describing study protocols, systematic reviews, editorials, doctoral theses, opinion articles, abstracts, posters or conference presentations.

Validity assessment

The extent to which a review can draw meaningful conclusions about the effects of an intervention depends on whether the data and results from the included studies are valid. Hence, we developed a novel method to systematically evaluate the validity of each individual study chosen based on our inclusion and exclusion criteria. We established seven quality criteria (QC) to create a scoring system for assessing both internal and external validity.

External validity refers to whether the study is asking an appropriate research question. To assess this, three predefined QC were employed to evaluate if the research questions in the reviewed studies were pertinent to answering the research questions posed in our review (QC5 to QC7).

Internal validity refers to whether a study appropriately answers its research question, which is closely linked to its methodological quality. Given that this review aimed to compile information from articles assessing the impact on health outcomes, it was assumed that the research questions should be related to health outcomes. Therefore, we evaluated their methodological ability to demonstrate valid and reliable differences in health outcomes, where present.

This capacity depends on various factors, including the use of appropriate methods for quantifying health outcomes, presenting them in comparison to a control group, and conducting statistical analyses to verify the statistical significance of observed differences. These principles, along with whether the study’s limitations were acknowledged, constituted the internal validity quality criteria (QC1 to QC4).

These QC were used to form a scoring system to determine the inclusion or exclusion of articles in this review, based on their validity. We set a minimum threshold of 3 out of 4 points for internal validity and 2 out of 3 points for external validity as the criteria for inclusion.

Quality criteria compliance was independently assessed by two researchers. In cases of disagreement, a third author reviewed the articles to confirm inclusion or exclusion.

Internal validity criteria

QC1 . Are health outcome obtaining methods well described?

1 point if well described, using validated scales.

0.5 points if adequately described but not using validated scales.

0 points if poorly described.

QC2 . Are health outcomes expressed relative to a control group with no ePRO symptom assessment (pre-post or parallel control group)?

1 point if affirmative.

0 points if negative.

QC3 . Is a statistical significance analysis performed for the obtained health outcomes?

QC4 . Are the study limitations presented?

1 point if the study limitations were detailed.

0.5 points if approached superficially.

0 points if not addressed.

External validity criteria

QC5 . Do the research objectives explicitly include patient-reported health outcomes as either primary or secondary measures?

1 point if main objectives involve patient-reported health outcome measures.

0.5 points if secondary objectives involve patient-reported health outcome measures.

QC6 . Does it address the methods by which patients receive advice for managing their symptoms?

1 point if well addressed.

0.5 points if superficially addressed.

QC7 . Does the article provide information that answers the proposed research questions?

1 point if the article contributed to answering the research questions.

0.5 points if it partially contributed.

0 points if it did not contribute to solving the research questions.

Study variables and data extraction

Data extraction, which served as the basis for our discussion and results, was carried out using a comparative table that included various variables: author name, publication year, study population, sample size, used app/web-interface, intended health-related endpoints, health results obtained by the intervention group compared with the control group, used scales and subscales, mean differences and statistical data.

Additionally, the authors collaboratively established a set of features that, in their collective perspective, an ideal symptom-management-focused Patient-Reported Outcome Measure (PROM) app/web interface should encompass. These features were documented in a 21-item checklist, and the extent to which the reviewed articles' apps complied with these criteria was assessed.

All authors collectively reviewed the data contained in these tables through group discussions and individual reviews.

Out of the initial 246 articles identified through our search strategy, 227 were excluded for not meeting the predetermined inclusion and exclusion criteria based on the title and abstract review. Subsequently, the remaining 19 articles underwent a thorough full-text evaluation and validity assessment (see figure 1 ). Among these, 11 were discarded as they did not meet our specified validity criteria, primarily due to external validity. 24–34 In other words, they did not contribute to addressing the research questions outlined in our review and did not meet the minimum external validity threshold (refer to table 1 for details). In no way does this imply that the scientific merit of the excluded studies is being questioned. They were excluded solely based on our predetermined criteria, which were established with the aim of providing an objective method for assessing validity.

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Quantitative results of the search protocol and study selection.

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Quality criteria compliance degree

Consequently, the remaining eight articles were included in our review, being subjected to detailed examination and data extraction. 1 7 8 35–39 A search update conducted in May 2024 confirmed that no further articles meeting the pre-specified inclusion and exclusion criteria had been found up to that date.

Attending to the design, all studies were controlled clinical trials including patients on a voluntary basis. None of the authors described a widespread adoption of ePRO monitoring apps in the routine oncology practice; hence, giving access to these apps was the cornerstone of the initiative carried out in the intervention group, as compared with the control group, who continued with the usual clinical care.

Table 2 and the online supplemental table encapsulate the information gleaned from these articles. The online supplemental table contains essential data to address the first research question concerning the health outcomes demonstrated through ePRO monitoring. It is evident that these studies consistently demonstrate improvements in symptom burden and overall symptom distress. 7 8 35 38 Notably, enhancements in HRQL and their impact on process of care measures are also noteworthy. 7 8 37 The most remarkable results, however, pertain to the improvements in overall survival. 37 40

Supplemental material

Included apps′ functionalities and healthcare team-initiated follow-up programmes

Table 2 compiles pertinent information to answer the second research question regarding the advantages provided by these applications and monitoring programmes to patients, and their contributions to improved health outcomes. The collected data suggests that these systems play a pivotal role in enabling timely interventions, more frequent than conventional practices, and in reducing communication barriers. 7 8 35 38 39

Notably, the reviewed literature did not provide information regarding the approval status of these apps by national regulatory agencies in their respective countries.

Through a meticulous analysis of existing literature, this review contributes valuable insights to the ongoing debate surrounding the integration of ePROs into routine oncology practice.

In this review, we pose two significant research queries regarding the clinical impact and operational capabilities of ePRO monitoring apps and web interfaces. Next, we delve into a comprehensive discussion of the insights gathered from the systematic review, structured in alignment with the research questions specified in the study protocol.

Research query 1: Have ePRO monitoring apps/web interfaces, aimed at symptom assessment, demonstrated positive health results when applied to adult cancer outpatients receiving systemic antineoplastic agents?

Our review of the literature indicates that ePRO monitoring apps designed for symptom control show positive impacts on health-related outcomes when applied to cancer patients undergoing systemic antineoplastic treatment on an outpatient basis. The reviewed data encompass studies involving a wide range of cancer types, including breast, colorectal, genitourinary, gynaecological, pancreatic, Hodgkin’s lymphoma, and non-Hodgkin's lymphoma, spanning both early and metastatic stages.

✓ Early or non-metastatic stage

Consistent improvements in symptom burden and overall symptom distress are observed in various studies, as measured by the Memorial Symptom Assessment Scale. 7 35 38 Enhancements in physical well-being are reported within a few weeks after the initiation of chemotherapy 1 and a reduction in the prevalence of symptoms is observed in both neoadjuvant 38 and adjuvant settings. 39 Some studies also note a reduction in anxiety and depression symptoms over time 35 ; other, however, fail to observe significant differences in symptom severity and interference. 36

HRQL outcomes are less consistent. Larger studies, such as the one conducted by Maguire et al. , report significant improvements in global HRQL across all cycles, as well as in physical and functional domains, as measured by the FACT-G scale. 7 In contrast, medium-sized and smaller studies do not consistently observe significant differences in global HRQL. 1 36 38 39 However, these studies do identify enhancements in specific HRQL domains, such as the QLQ-C30 emotional functioning subscale 38 39 and favourable changes on the EuroQol EQ-5D Visual Analogue Scale. 1

Additional outcomes include improvements in various supportive care needs 7 and self-efficacy domains. 1 7 39 Furthermore, a noteworthy finding is an enhanced adherence rate to oral therapies among patients who reported baseline adherence issues and elevated anxiety symptoms. 36

✓ Metastatic setting

Basch et al, demonstrate that ePRO monitoring leads to improvement in physical function, symptom control and HRQL in the metastatic setting. It also impacts on process of care measures, reducing emergency department visits, hospitalisations, and prolonging the time patients remain on chemotherapy. 8 37

The most significant results, however, are those that reveal an increase in overall survival (OS). In the study by Basch et al., the percentage of patients alive at 1 year increased by 6%. 37 Furthermore, a post-hoc analysis confirms that these benefits are sustained over time, with a median 7 year follow-up showing a mean 5 month OS improvement, 40 underscoring the durability of the initially observed benefits.

Research query 2. What kind of advantages do these applications offer to patients, both through their functionalities and through the follow-up programmes that the healthcare team offers?

Most ePRO monitoring apps facilitate real-time symptom reporting to patients through standardised questionnaires, thereby enabling the healthcare team to continuously monitor the severity of symptoms over time. 1 7 35 37–39 Patient reports are linked to stratified alert systems, that trigger contact protocols with the healthcare team when symptom thresholds are exceeded. 1 7 8 37–39 Additionally, these apps typically provide automated and personalised feedback to patients, utilising clinical algorithms to provide specific recommendations based on reported symptom levels. 1 7 8 35 38 39

The enhancement of health outcomes is closely related to the reduction of communication barriers and the more frequent and timely interventions provided by the healthcare team, as compared with conventional practices. 7 8 35 38 39 Some studies even establish maximum response times to alerts by the healthcare team, which proves to be an interesting approach. 7 35 38 39 Equally important is the provision of hospital contact instructions to patients for urgent needs outside of alert handling hours. 1 37–39

Regular reminders sent to patients represent a widely adopted strategy aimed at motivating app usage and enhancing adherence to symptom reporting. 1 8 36–39 The reported data not only contribute to improved symptom management but also enable healthcare teams to address patients' physical and psychological needs, 1 7 8 35 38 39 and emotional and wellness support. 7 8 35 36

For patients undergoing oral therapies, some apps send regular reminders with each oral antineoplastic agent (OAA) intake, enabling patients to track OAA consumption, note any omissions, and provide reasons for non-adherence. 36 Ideally, such a system should alert the healthcare team in case of poor adherence to OAA.

The findings presented in our review offer compelling evidence that ePRO monitoring yields tangible improvements in health outcomes across diverse cancer settings, spanning both early and metastatic stages. Clinical benefits on symptom burden, HRQL, and even overall survival are becoming increasingly evident. This reinforces the idea that the clinical advantages of these systems may outweigh any associated costs or logistical challenges.

In the context of identifying the most beneficial components of web-based support systems for patients, the currently available evidence suggests that the key role played by these systems is in facilitating timely interventions, more frequent than in conventional practices, and reducing communication barriers. Additionally, these systems empower patients to actively engage in their self-care, fostering a sense of ownership and involvement in their health management.

However, our review also highlights areas for potential innovation within the ePRO landscape. It is noteworthy that several features identified by the authors as ideal for inclusion in a symptom-management-focused PROM app were not commonly found in the articles under review. These particular features have been recognised as potential areas for improvement in future apps and encompass the following.

First, among the apps examined, none have yet embraced the concept of tailoring personalised symptom-related surveys through predictive symptom and adverse effect analysis, specifically customised for distinct cancer types and treatments. This innovative approach not only streamlines the questionnaire, focusing on the most pertinent and anticipated aspects but also avoids overburdening patients with less relevant inquiries. Moreover, the potential for integrating artificial intelligence and real-world data to develop predictive, personalised, and targeted interventions represents an exciting avenue for future research, promising to further enhance patient outcomes and care efficiency.

Second, the inclusion of clinical parameter monitoring within ePRO apps has the potential to broaden their utility, facilitating a comprehensive approach to cancer care management. Wearable devices, such as smartwatches with capabilities to measure vital signs such as blood pressure, heart rate, and body temperature, could emerge as valuable components in advancing this approach.

Thirdly, a critical factor in promoting the integration of ePROs into routine clinical practice is to ensure their incorporation into electronic medical records. This would enable healthcare teams to access patient-reported outcomes effortlessly, reducing administrative burdens and consolidating all of the patient’s clinical information within a unified platform. Regrettably, our review reveals that progress in this area has been modest, indicating a clear need for streamlining these processes.

Finally, patients would highly appreciate the integration of a calendar feature that seamlessly synchronises with electronic medical records, automatically presenting all their medical appointments. The expedited processing of appointment requests for clinical consultations through the ePROs monitoring app would also be valued by patients. These enhancements have the potential to greatly enhance the overall patient experience and convenience.

Study limitations

The search strategy was limited to PubMed, potentially excluding relevant studies from other databases.

The analysis of data in this systematic review poses difficulties in making direct comparisons among the clinical outcomes reported in the reviewed articles. These challenges stem from two main factors: the significant variability in the measurement scales used to assess health outcomes and the observed heterogeneity in the study populations. The studies included in this review cover a diverse spectrum of neoplastic conditions and various stages of cancer, adding complexity to the task of drawing direct comparisons.

Furthermore, based on the findings, we are unable to provide insights into which specific components of web-based support systems offer the greatest benefits to patients. Future research should aim to explore these specific components in greater detail, seeking to establish direct connections between them and measurable health outcomes. It is important to recognise the inherent complexity in demonstrating such associations, making this a challenging endeavour for future investigations.

To conclude, our review reaffirms the transformative potential of ePRO systems in oncology. It calls for ongoing research and innovation to unlock the full spectrum of their capabilities and underscores the imperative of leveraging these technologies to enhance patient care, improve health outcomes, and drive efficiency in healthcare delivery.

Moreover, the COVID-19 pandemic has emphasised the urgency of accelerating the adoption of e-PROMs and eHealth interventions for the safe and efficient delivery of cancer care. Fortunately, governments and healthcare organisations are recognising the disruptive potential of digital health technologies and are actively adapting to this ever-evolving landscape, further highlighting that ePROs are poised to play a pivotal role in the future of cancer care.

Ethics statements

Patient consent for publication.

Not applicable.

Ethics approval

Acknowledgments.

We extend our gratitude to the scientific community for their valuable contributions to electronic symptom monitoring across different settings. Their prior work has been pivotal in shaping the context for this review.

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EAHP Statement 5: Patient Safety and Quality Assurance.

Contributors All authors contributed to the study conception and design.The process of reviewing abstracts and titles to determine their inclusion or exclusion in this study, as well as the subsequent full-text evaluation of potentially eligible articles for quality assessment, was conducted by MUA and KAT. In case of disagreement, ACRA reviewed to confirm inclusion or exclusion. Data collection and analysis were performed by MUA, KAT and ACRA. The first draft of the manuscript was written by MUA and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. ChatGPT 3.5 was used to translate content from Spanish to English and to help restructure some paragraphs, but not for creating new content.

Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests None declared.

Provenance and peer review Not commissioned; externally peer reviewed.

Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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The Best Books of the Year (So Far)

The nonfiction and novels we can’t stop thinking about.

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By The New York Times Books Staff

• May 24, 2024

Fiction | Nonfiction

We’re almost halfway through 2024 and we at The Book Review have already written about hundreds of books. Some of those titles are good. Some are very good. And then there are the following.

We suspect that some (though certainly not all) will be top of mind when we publish our end-of-year, best-of lists. For more thoughts on what to read next, head to our book recommendation page .

James , by Percival Everett

In this reworking of the “Adventures of Huckleberry Finn,” Jim, the enslaved man who accompanies Huck down the Mississippi River, is the narrator, and he recounts the classic tale in a language that is his own, with surprising details that reveal a far more resourceful, cunning and powerful character than we knew.

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Good Material , by Dolly Alderton

Alderton’s novel, about a 35-year-old struggling to make sense of a breakup, delivers the most delightful aspects of romantic comedy — snappy dialogue, realistic relationship dynamics, funny meet-cutes and misunderstandings — and leaves behind clichéd gender roles and the traditional marriage plot.

Martyr! , by Kaveh Akbar

A young Iranian American aspiring poet and recovering addict grieves his parents’ deaths while fantasizing about his own in Akbar’s remarkable first novel, which, haunted by death, also teems with life — in the inventive beauty of its sentences, the vividness of its characters and the surprising twists of its plot.

The Hunter , by Tana French

For Tana French fans, every one of the thriller writer’s twisty, ingenious books is an event. This one, a sequel to “The Searcher,” once again sees the retired Chicago cop Cal Hooper, a perennial outsider in the Irish west-country hamlet of Ardnakelty, caught up in the crimes — seen and unseen — that eat at the seemingly picturesque village.

Wandering Stars , by Tommy Orange

This follow-up to Orange’s debut, “There There,” is part prequel and part sequel; it trails the young survivor of a 19th-century massacre of Native Americans, chronicling not just his harsh fate but those of his descendants. In its second half, the novel enters 21st-century Oakland, following the family in the aftermath of a shooting.

Headshot , by Rita Bullwinkel

Set at a women’s boxing tournament in Reno, Nev., this novel centers on eight contestants, and the fights — physical and emotional — they bring to the ring. As our critic wrote: This story’s impact “lasts a long time, like a sharp fist to your shoulder.”

Beautyland , by Marie-Helene Bertino

In 1970s Philadelphia, an alien girl sent to Earth before she’s born communicates with her fellow life-forms via fax as she helps gather intel about whether our planet is habitable. This funny-sad novel follows the girl and her single mother as they find the means to persevere.

Knife: Meditations After an Attempted Murder , by Salman Rushdie

In his candid, plain-spoken and gripping new memoir, Rushdie recalls the attempted assassination he survived in 2022 during a presentation about keeping the world’s writers safe from harm. His attacker had piranhic energy. He also had a knife. Rushdie lost an eye, but he has slowly recovered thanks to the attentive care of doctors and the wife he celebrates here.

Everyone Who Is Gone Is Here: The United States, Central America, and the Making of a Crisis , by Jonathan Blitzer

This urgent and propulsive account of Latin American politics and immigration makes a persuasive case for a direct line from U.S. foreign policy in Central America to the current migrant crisis.

The Wide Wide Sea: Imperial Ambition, First Contact and the Fateful Final Voyage of Captain James Cook , by Hampton Sides

By the time he made his third Pacific voyage, the British explorer James Cook had maybe begun to lose it a little. The scientific aims of his first two trips had shifted into something darker. According to our reviewer, the historian Hampton Sides “isn’t just interested in retelling an adventure tale. He also wants to present it from a 21st-century point of view. ‘The Wide Wide Sea’ fits neatly into a growing genre that includes David Grann’s ‘ The Wager ’ and Candice Millard’s ‘ River of the Gods ,’ in which famous expeditions, once told as swashbuckling stories of adventure, are recast within the tragic history of colonialism .”

The Rebel’s Clinic: The Revolutionary Lives of Frantz Fanon , by Adam Shatz

This absorbing biography of the Black psychiatrist, writer and revolutionary Frantz Fanon highlights a side of him that’s often eclipsed by his image as a zealous partisan — that of the caring doctor, who ran a secret clinic for Algerian rebels.

Fi: A Memoir , by Alexandra Fuller

In her fifth memoir, Fuller describes the sudden death of her 21-year-old son. Devastating as this elegant and honest account may be — it’s certainly not for the faint of heart — it also leaves the reader with a sense of having known a lovely and lively young man.

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New Orleans is a thriving hub for festivals, music and Creole cuisine. The novelist Maurice Carlos Ruffin shared books that capture the city’s many cultural influences .

Joseph O’Neill’s fiction incorporates his real-world interests in ways that can surprise even him. His latest novel, “Godwin,” is about an adrift hero searching for a soccer superstar .

Keila Shaheen’s self-published best seller book, “The Shadow Work Journal,” shows how radically book sales and marketing have been changed by TikTok .

John S. Jacobs was a fugitive, an abolitionist — and the brother of the canonical author Harriet Jacobs. Now, his own fierce autobiography has re-emerged .

Each week, top authors and critics join the Book Review’s podcast to talk about the latest news in the literary world. Listen here .

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