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What are systematic reviews?

Watch this video from   Cochrane Consumers and Communication to learn what systematic reviews are, how researchers prepare them, and why they’re an important part of making informed decisions about health - for everyone. 

Cochrane evidence, including our systematic reviews, provides a powerful tool to enhance your healthcare knowledge and decision making. This video from Cochrane Sweden explains a bit about how we create health evidence and what Cochrane does. 

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1.2.2  What is a systematic review?

A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question.  It  uses explicit, systematic methods that are selected with a view to minimizing bias, thus providing more reliable findings from which conclusions can be drawn and decisions made (Antman 1992, Oxman 1993) . The key characteristics of a systematic review are:

a clearly stated set of objectives with pre-defined eligibility criteria for studies;

an explicit, reproducible methodology;

a systematic search that attempts to identify all studies that would meet the eligibility criteria;

an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and

a systematic presentation, and synthesis, of the characteristics and findings of the included studies.

Many systematic reviews contain meta-analyses. Meta-analysis is the use of statistical methods to summarize the results of independent studies (Glass 1976). By combining information from all relevant studies, meta-analyses can provide more precise estimates of the effects of health care than those derived from the individual studies included within a review (see Chapter 9, Section 9.1.3 ). They also facilitate investigations of the consistency of evidence across studies, and the exploration of differences across studies.

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Cochrane handbook for systematic reviews of interventions.

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Methodological Expectations for Cochrane Intervention Reviews (MECIR)

Contact the editors, how to cite the handbook, permission to re-use material from the handbook, previous versions, access the cochrane handbook  for systematic reviews of interventions.

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About the Handbook

The Cochrane Handbook for Systematic Reviews of Interventions is the official guide that describes in detail the process of preparing and maintaining Cochrane systematic reviews on the effects of healthcare interventions. All authors should consult the Handbook for guidance on the methods used in Cochrane systematic reviews. The Handbook includes guidance on the standard methods applicable to every review (planning a review, searching and selecting studies, data collection, risk of bias assessment, statistical analysis, GRADE and interpreting results), as well as more specialised topics (non-randomized studies, adverse effects, complex interventions, equity, economics, patient-reported outcomes, individual patient data, prospective meta-analysis, and qualitative research).

Last updated: 22 August, 2023

Key aspects of Handbook guidance are collated as the Methodological Expectations for Cochrane Intervention Reviews (MECIR). These provide core standards that are generally expected of Cochrane reviews. Each MECIR item includes a link to a relevant Handbook chapter.

For further information and for any Handbook enquiries please contact: [email protected] .

The Handbook editorial team includes: Julian Higgins and James Thomas (Senior Scientific Editors); Jacqueline Chandler, Miranda Cumpston,  Tianjing Li , Matthew Page and Vivian Welch (Associate Scientific Editors); Ella Flemyng (Managing Editor).

To cite the full Handbook online, please use:

Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.4 (updated August 2023). Cochrane, 2023. Available from www.training.cochrane.org/handbook.

To cite the print edition of the Handbook,  please use:

Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions . 2nd Edition. Chichester (UK): John Wiley & Sons, 2019.

Details of how to cite individual chapters in either of these versions are available in each chapter.

Academic or other non-commercial re-use of Handbook material You do not need to request permission to use short quotations (though these must be appropriately cited), or to cite the Handbook as a source. See How to cite the Handbook . If you intend to reproduce material from the Handbook using screenshots, including exact figures or tables from the Handbook or including lengthy direct quotations (more than 5 lines of text), then please fill in this form to request permission to re-use material from the Handbook . This will be sent to the Cochrane Support team who will notify Julian Higgins or James Thomas, the Handbook Senior Editors, as appropriate. If approved, these requests will be granted free of charge on condition that the source is acknowledged.

Commercial re-use of Handbook material Commercial re-use includes any use of the Handbook that will be used in a product for which there is a monetary fee, and/or where it is associated in any way with any product or service. For all enquiries related to the commercial re-use of Handbook material please contact Wiley Global Permissions , John Wiley & Sons, Ltd.

Details on how the Handbook has changed compared to previous versions can be found on the Versions and changes   page. More information on the process for updating the Handbook can be found here . 

Archived copies of the following previous versions of the Handbook are available:

• Version 6.3 : February 2022 [browsable] 
• Version 6.2 : February 2021 [browsable] 
• Version 6.1 : September 2020 [browsable]
• Version 6.0 : July 2019 [browsable]
• Version 5.2 : June 2017 [PDF]
• Version 5.1: March 2011 [browsable]
• Version 5.0.2: September 2009 [browsable]
• Version 5.0.0: February 2008 [browsable]
• Version 4.2.6: September 2006 [PDF] 2.8MB
• Version 4.2.1 : December 2003 [PDF]

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• Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy

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What are systematic reviews.

 "What are systematic reviews?" If you’re a Cochrane contributor and have ever attempted to explain Cochrane’s work to someone, chances are you’ve tried to answer this question. And if you’re reading this because you’re new to Cochrane and the work we do, you may be wondering about this too.

Thanks to a team of creative colleagues from Cochrane Consumers and Communication , we’re pleased to share a video resource which answers this question clearly and simply for people who may not be familiar with the concept of systematic reviews: what they are, how researchers prepare them, and why they’re an important part of making informed decisions about health - for everyone. You can find this video on Cochrane’s YouTube channel , and we hope you’ll share and spread the word about the importance of evidence!

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