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Cannabis use associated with lower mortality among hospitalized Covid-19 patients using the national inpatient sample: an epidemiological study

Prior reports indicate that modulation of the endocannabinoid system (ECS) may have a protective benefit for Covid-19 patients. However, associations between cannabis use (CU) or CU not in remission (active ca...

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State licenses for medical marijuana dispensaries: neighborhood-level determinants of applicant quality in Missouri

When state governments impose quotas on commercial marijuana licenses, regulatory commissions use an application process to assess the feasibility of prospective businesses. Decisions on license applications a...

Effect of organic biostimulants on cannabis productivity and soil microbial activity under outdoor conditions

In 2019 and 2020, we investigated the individual and combined effects of two biofertilizers (manure tea and bioinoculant) and one humic acid (HA) product on cannabis biochemical and physiological parameters an...

Neuroimaging studies of cannabidiol and potential neurobiological mechanisms relevant for alcohol use disorders: a systematic review

The underlying neurobiological mechanisms of cannabidiol’s (CBD) management of alcohol use disorder (AUD) remains elusive.

A narrative review of the therapeutic and remedial prospects of cannabidiol with emphasis on neurological and neuropsychiatric disorders

The treatment of diverse diseases using plant-derived products is actively encouraged. In the past few years, cannabidiol (CBD) has emerged as a potent cannabis-derived drug capable of managing various debilit...

Comment on “Hall et al., Topical cannabidiol is well tolerated in individuals with a history of elite physical performance and chronic lower extremity pain”

A national study of clinical discussions about cannabis use among veteran patients prescribed opioids.

The Veterans Health Administration tracks urine drug tests (UDTs) among patients on long-term opioid therapy (LTOT) and recommends discussing the health effects of cannabis use.

Evaluation of dispensaries’ cannabis flowers for accuracy of labeling of cannabinoids content

Cannabis policies have changed drastically over the last few years with many states enacting medical cannabis laws, and some authorizing recreational use; all against federal laws. As a result, cannabis produc...

Oral Cannabis consumption and intraperitoneal THC:CBD dosing results in changes in brain and plasma neurochemicals and endocannabinoids in mice

While the use of orally consumed Cannabis, cannabidiol (CBD) and tetrahydrocannabinol (THC) containing products, i.e. “edibles”, has expanded, the health consequences are still largely unknown. This study examine...

Recent advances in the development of portable technologies and commercial products to detect Δ 9 -tetrahydrocannabinol in biofluids: a systematic review

The primary components driving the current commercial fascination with cannabis products are phytocannabinoids, a diverse group of over 100 lipophilic secondary metabolites derived from the cannabis plant. Alt...

Associations between simultaneous use of alcohol and cannabis and cannabis-related problems in 2014–2016: evidence from the Washington panel survey

To address the research question of how simultaneous users of alcohol and cannabis differ from concurrent users in risk of cannabis use problems after the recreational marijuana legalization in Washington State.

Characteristics of patients with non-cancer pain and long-term prescription opioid use who have used medical versus recreational marijuana

Marijuana use is increasingly common among patients with chronic non-cancer pain (CNCP) and long-term opioid therapy (LTOT). We determined if lifetime recreational and medical marijuana use were associated wit...

Cannabis use, decision making, and perceptions of risk among breastfeeding individuals: the Lactation and Cannabis (LAC) Study

Our primary objective was to understand breastfeeding individuals’ decisions to use cannabis. Specifically, we investigated reasons for cannabis use, experiences with healthcare providers regarding use, and po...

Distribution of legal retail cannabis stores in Canada by neighbourhood deprivation

In legal cannabis markets, the distribution of retail stores has the potential to influence transitions from illegal to legal sources as well as consumer patterns of use. The current study examined the distrib...

Examining attributes of retailers that influence where cannabis is purchased: a discrete choice experiment

With the legalization of cannabis in Canada, consumers are presented with numerous purchase options. Licensed retailers are limited by the Cannabis Act and provincial regulations with respect to offering sales...

Effects of acute cannabis inhalation on reaction time, decision-making, and memory using a tablet-based application

Acute cannabis use has been demonstrated to slow reaction time and affect decision-making and short-term memory. These effects may have utility in identifying impairment associated with recent use. However, th...

Analysis of social media compliance with cannabis advertising regulations: evidence from recreational dispensaries in Illinois 1-year post-legalization

In the USA, an increasing number of states have legalized commercial recreational cannabis markets, allowing a private industry to sell cannabis to those 21 and older at retail locations known as dispensaries....

Comparison of perceptions in Canada and USA regarding cannabis and edibles

Canada took a national approach to recreational cannabis that resulted in official legalization on October 17, 2018. In the United States (US), the approach has been more piecemeal, with individual states pass...

Attitudes of Swiss psychiatrists towards cannabis regulation and medical use in psychiatry: a cross-sectional study

Changes in regulation for cannabis for nonmedical use (CNMU) are underway worldwide. Switzerland amended the law in 2021 allowing pilot trials evaluating regulative models for cannabis production and distribut...

Cannabis and pathologies in dogs and cats: first survey of phytocannabinoid use in veterinary medicine in Argentina

In animals, the endocannabinoid system regulates multiple physiological functions. Like humans, animals respond to preparations containing phytocannabinoids for treating several conditions. In Argentina, laws ...

The holistic effects of medical cannabis compared to opioids on pain experience in Finnish patients with chronic pain

Medical cannabis (MC) is increasingly used for chronic pain, but it is unclear how it aids in pain management. Previous literature suggests that MC could holistically alter the pain experience instead of only ...

The potential for Ghana to become a leader in the African hemp industry

Global interest in hemp cultivation and utilization is on the rise, presenting both challenges and opportunities for African countries. This article focuses on Ghana’s potential to establish a thriving hemp se...

Cannabinoid hyperemesis syndrome presenting with ventricular bigeminy

The is a case of a 28-year-old male presenting to an emergency department (ED) via emergency medical services (EMS) with a chief complaint of “gastritis.” He was noted to have bigeminy on the pre-arrival EMS e...

Driving-related behaviors, attitudes, and perceptions among Australian medical cannabis users: results from the CAMS 20 survey

Road safety is an important concern amidst expanding worldwide access to legal cannabis. The present study reports on the driving-related subsection of the Cannabis as Medicine Survey 2020 (CAMS-20) which surv...

High levels of pesticides found in illicit cannabis inflorescence compared to licensed samples in Canadian study using expanded 327 pesticides multiresidue method

As Cannabis was legalised in Canada for recreational use in 2018 with the implementation of the Cannabis Act , Regulations were put in place to ensure safety and consistency across the cannabis industry. This incl...

Correction: Potency and safety analysis of hemp delta-9 products: the hemp vs. cannabis demarcation problem

The original article was published in Journal of Cannabis Research 2023 5 :29

Cannabis use for exercise recovery in trained individuals: a survey study

Cannabis use, be it either cannabidiol (CBD) use and/or delta-9-tetrahydrocannabinol (THC) use, shows promise to enhance exercise recovery. The present study aimed to determine if individuals are using CBD and...

The COVID-19 pandemic and cannabis use in Canada―a scoping review

Since the start of the COVID-19 pandemic in Canada, the cannabis industry has adapted to public health emergency orders which had direct and indirect consequences on cannabis consumption. The objective of this...

DMSO potentiates the suppressive effect of dronabinol on sleep apnea and REM sleep in rats

Dimethyl sulfoxide (DMSO) is an amphipathic molecule with innate biological activity that also is used to dissolve both polar and nonpolar compounds in preclinical and clinical studies. Recent investigations o...

Potency and safety analysis of hemp delta-9 products: the hemp vs. cannabis demarcation problem

Hemp-derived delta-9 tetrahydrocannabinol (∆ 9 THC) products are freely available for sale across much of the USA, but the federal legislation allowing their sale places only minimal requirements on companies. Pro...

The Correction to this article has been published in Journal of Cannabis Research 2023 5 :33

A comparison of advertised versus actual cannabidiol (CBD) content of oils, aqueous tinctures, e-liquids and drinks purchased in the UK

Cannabidiol (CBD)-containing products are sold widely in consumer stores, but concerns have been raised regarding their quality, with notable discrepancies between advertised and actual CBD content. Informatio...

Cannabis sativa demonstrates anti-hepatocellular carcinoma potentials in animal model: in silico and in vivo studies of the involvement of Akt

Targeting protein kinase B (Akt) and its downstream signaling proteins are promising options in designing novel and potent drug candidates against hepatocellular carcinoma (HCC). The present study explores the...

Conflicting forces in the implementation of medicinal cannabis regulation in Uruguay

Uruguay is widely known as a pioneer country regarding cannabis regulation policies, as it was the first state to regulate the cannabis market for both recreational and medicinal purposes in 2013. However, not...

Why a distinct medical stream is necessary to support patients using cannabis for medical purposes

Since 2001, Canadians have been able to obtain cannabis for medical purposes, initially through the Access to Cannabis for Medical Purposes Regulations (ACMPR). The Cannabis Act (Bill C-45) came into force on ...

Propylene glycol and Kolliphor as solvents for systemic delivery of cannabinoids via intraperitoneal and subcutaneous routes in preclinical studies: a comparative technical note

Substance administration to laboratory animals necessitates careful consideration and planning in order to enhance agent distribution while reducing any harmful effects from the technique. There are numerous m...

No difference in COVID-19 treatment outcomes among current methamphetamine, cannabis and alcohol users

Poor outcomes of COVID-19 have been reported in older males with medical comorbidities including substance use disorder. However, it is unknown whether there is a difference in COVID-19 treatment outcomes betw...

Cannabis for morning sickness: areas for intervention to decrease cannabis consumption during pregnancy

Cannabis use during pregnancy is increasing, with 19–22% of patients testing positive at delivery in Colorado and California. Patients report using cannabis to alleviate their nausea and vomiting, anxiety, and...

The therapeutic potential of purified cannabidiol

The use of cannabidiol (CBD) for therapeutic purposes is receiving considerable attention, with speculation that CBD can be useful in a wide range of conditions. Only one product, a purified form of plant-deri...

Naturalistic examination of the anxiolytic effects of medical cannabis and associated gender and age differences in a Canadian cohort

The aim of the current study was to examine patterns of medical cannabis use in those using it to treat anxiety and to investigate if the anxiolytic effects of cannabis were impacted by gender and/or age.

The Desert Whale: the boom and bust of hemp in Arizona

This paper examines the factors that led to the collapse of hemp grown for cannabidiol (CBD) in Arizona, the United States of America (USA), and particularly in Yuma County, which is a well-established agricul...

Reasonable access: important characteristics and perceived quality of legal and illegal sources of cannabis for medical purposes in Canada

Throughout the past two decades of legal medical cannabis in Canada, individuals have experienced challenges related to accessing legal sources of cannabis for medical purposes. The objective of our study was ...

The reintroduction of hemp in the USA: a content analysis of state and tribal hemp production plans

The reintroduction of Cannabis sativa L . in the form of hemp (< 0.3% THC by dry weight) into the US agricultural sector has been complex and remains confounded by its association with cannabis (> 0.3% THC by dry ...

The Cannabis sativa genetics and therapeutics relationship network: automatically associating cannabis-related genes to therapeutic properties through chemicals from cannabis literature

Understanding the genome of Cannabis sativa holds significant scientific value due to the multi-faceted therapeutic nature of the plant. Links from cannabis gene to therapeutic property are important to establish...

Self-reported adverse events associated with ∆ 8 - Tetrahydrocannabinol (Delta-8-THC) Use

There is an expanding unregulated market for a psychotropic compound called ∆ 8 -Tetrahydrocannabinol (delta-8-THC) that is being derived from hemp, but a summary of adverse events related to delta-8-THC has not be...

The safety of lookalikes: a new THC beverage enhancer and a non-THC counterpart

A new tetrahydrocannabinol (THC) beverage enhancer is available to medical and recreational cannabis consumers across the US. Beverage enhancers that do not contain THC, but instead contain flavored concentrat...

Modeling a pesticide remediation strategy for preparative liquid chromatography using high-performance liquid chromatography

Cannabis sativa L. also known as industrial hemp, is primarily cultivated as source material for cannabinoids cannabidiol (CBD) and ∆9-tetrahydrocannabinol (∆9-THC). Pesticide contamination during plant growth is...

Glandular trichome development, morphology, and maturation are influenced by plant age and genotype in high THC-containing cannabis ( Cannabis sativa L.) inflorescences

Glandular capitate trichomes which form on bract tissues of female inflorescences of high THC-containing Cannabis sativa L. plants are important sources of terpenes and cannabinoids. The influence of plant age an...

Topical cannabidiol is well tolerated in individuals with a history of elite physical performance and chronic lower extremity pain

Cannabidiol (CBD) is a potential therapeutic for pain management. Yet, there exists a dearth of studies of its tolerability and efficacy, especially in special populations. Former elite athletes are a special ...

“It doesn’t make any sense to even try”: the disruptive impact of COVID-19’s first wave on people with chronic pain using medical cannabis in New York

The COVID-19 pandemic disrupted health care but it is unknown how it impacted the lives of people using medical cannabis for chronic pain.

Unintentional ingestion of putative delta-8 tetrahydrocannabinol by two youth requiring critical care: a case report

Delta-8 tetrahydrocannabinol (THC) is a psychoactive cannabinoid from the cannabis plant that can be synthetically converted from cannabidiol (CBD). Most states permit the full or restricted sale of hemp and h...

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• 17 October 2018

The wide world of weed research

• Elie Dolgin 0

Elie Dolgin is a Canadian-born science journalist in Somerville, Massachusetts.

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Canada has just become the second country in the world, after Uruguay, to legalize cannabis for all uses — a move that has prompted a flood of funding for basic research into cultivation of the plant, and a clamour for scientists with expertise in genetics, bioengineering and growing practices .

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doi: https://doi.org/10.1038/d41586-018-07081-x

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Mechoulam, R. & Shvo, Y. Tetrahedron 19, 2073–2078 (1963).

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After 50 Years, U.S. Opens The Door To More Cannabis Crops For Scientists

More than 30 states have medical marijuana programs — yet scientists are only allowed to use cannabis plants from one U.S. source for their research. That's set to change, as the federal government begins to add more growers to the mix. Drew Angerer/Getty Images hide caption

More than 30 states have medical marijuana programs — yet scientists are only allowed to use cannabis plants from one U.S. source for their research. That's set to change, as the federal government begins to add more growers to the mix.

After more than 50 years, the federal government is lifting a roadblock to cannabis research that scientists and advocates say has hindered rigorous studies of the plant and possible drug development.

Since 1968, U.S. researchers have been allowed to use cannabis from only one domestic source : a facility based at the University of Mississippi, through a contract with the National Institute on Drug Abuse (NIDA).

That changed earlier this month, when the Drug Enforcement Administration announced it's in the process of registering several additional American companies to produce cannabis for medical and scientific purposes.

It's a move that promises to accelerate understanding of the plant's health effects and possible therapies for treating conditions — chronic pain, the side effects of chemotherapy, multiple sclerosis and mental illness, among many others — that are yet to be well studied .

Shots - Health News

How one boy's fight with epilepsy led to the first marijuana-derived pharmaceutical.

"This is a momentous decision," says Rick Doblin, executive director of the Multidisciplinary Association for Psychedelic Studies (MAPS), which has spearheaded research into other Schedule 1 drugs — the most restrictive class of controlled substance, which the federal government defines as "drugs with no currently accepted medical use."

"This is the last political obstruction of research with Schedule 1 drugs," he says.

About one-third of Americans currently live in a state where recreational marijuana is legal — and more than 30 states have medical marijuana programs . Yet scientists still aren't allowed to simply use the cannabis sold at state-licensed dispensaries for their clinical research because cannabis remains illegal under federal law.

Medical Marijuana's 'Catch-22': Limits On Research Hinder Patient Relief

"It is a big disconnect," says Dr. Igor Grant , a psychiatry professor and director of the Center for Medicinal Cannabis Research at University of California, San Diego.

The new DEA decision doesn't resolve the conflict between federal and state laws, but it does offer researchers a new, federally sanctioned pipeline for more products and strains of cannabis.

"We'll see a decade or more of explosive cannabis research and potential new therapies," says Dr. Steve Groff, founder and chairman of Groff North America , one of three companies that has publicly announced it has preliminary approval from the federal government to cultivate cannabis for research.

A long-running fight to overturn federal "monopoly"

Despite their efforts, scientists have encountered administrative and legal hurdles to growing pharmaceutical-grade cannabis for decades.

In 2001, Dr. Lyle Craker, a prominent plant biologist, first applied for a license to cultivate marijuana for research — only to encounter years of delay that kicked off a prolonged court battle with the DEA, which has to greenlight research into Schedule 1 drugs like cannabis.

"There's thousands of different cannabis varieties that all have unique chemical profiles and produce unique clinical effects, but we didn't have access to that normal diversity," says Dr. Sue Sisley , a cannabis researcher and president of the Scottsdale Research Institute, which also received preliminary DEA approval to produce cannabis for research.

Only in 2016 did the federal government signal a change in policy that would open the door for new growers, but applications to do so languished for years. Craker and others ended up suing the federal government over the delay.

Psychiatrist Explores Possible Benefits Of Treating PTSD With Ecstasy Or Cannabis

Sisley has long taken issue with the supply of cannabis coming from the NIDA facility in Mississippi — in particular, how it's processed. She used cannabis produced there in her recently published clinical trial on treating PTSD in military veterans.

She describes the product as an "anemic" greenish powder.

"It's very difficult to overcome the placebo effect when you have something that diluted," she says.

The 76-person study, which took 10 years to complete, concluded that smoked cannabis was generally well tolerated and did not lead to deleterious effects in this group. But it also did not find any statistically significant difference in abating the symptoms of PTSD when compared to a placebo.

For Grant of UCSD, the problem with the long-standing supply of cannabis isn't so much the quality, but the lack of different products like edibles and oils and of cannabis strains with varying concentrations of CBD and THC, the plant's main psychoactive ingredient.

"We don't have enough research on the kind of marijuana products that people in the real world are using," he says.

As CBD Oils Become More Popular, The FDA Considers Whether To Set New Rules

Because of the limited domestic supply, some researchers have resorted to importing cannabis from outside the U.S. — a legal but wildly counterintuitive arrangement that is "arduous" and prone to hiccups, says Sisley.

The constraints on research cannabis also has impeded the pathway to drug development because the NIDA facility's cannabis could only be used for academic research, not for prescription drug development . A drug studied in phase 3 clinical trials — what's required before submitting for approval from the Food and Drug Administration — must be the same as what's later marketed.

"The NIDA monopoly has primarily been why we have medical marijuana in the states, but we don't have medical marijuana through the FDA," says Doblin of MAPS. "It's a fundamental change that we can now have drug development with domestic supplies."

A few barriers still remain

The few companies that will soon land DEA spots to cultivate cannabis have an eager marketplace of researchers who are "clamoring" for the chance to study the scientific properties and medical potential of the plant, says Groff, whose company is up for DEA approval and who also has an FDA project to study the antimicrobial properties of cannabis for killing dangerous bacteria like MRSA .

By the end of next year, Groff anticipates his company will be producing up to 5,000 pounds of marijuana per year, offering researchers a "full menu of customizable options."

Biopharmaceutical Research Company — a third company that will soon cultivate cannabis with a DEA license — already has dozens of agreements in place with U.S. researchers and is hearing from more academic institutions, drugmakers and biotech companies in the wake of the change in policy, says CEO George Hodgin.

"Now there's a very clear, approved and legal path for them to legally enter the cannabis space in the United States," says Hodgin.

The Coronavirus Crisis

'illegal to essential': how the coronavirus is boosting the legal cannabis industry.

Washington State University's Center for Cannabis Policy, Research and Outreach is one of the places that expects to eventually procure cannabis from Hodgin's business.

"It's definitely a big step in the right direction because the industry is moving much faster than we are in research," says Michael McDonell , an associate professor of medicine and director of the university's cannabis center.

But he also points out that even with more growers coming online, it's still by no means easy to study cannabis, because researchers need a special license when working with a Schedule 1 drug and grants to conduct these studies are hard to come by.

Despite the widespread use of marijuana in the U.S., research into the medical potential of other Schedule 1 drugs like MDMA (ecstasy) is much further along than cannabis .

UCSD's Grant says the biggest leap forward for research would come from moving cannabis out of the Schedule 1 drug classification. "If that were to happen," he says, "that would solve a lot of these problems that we've been talking about."

• medical cannabis
• medical marijuana

March 1, 2024

Is Marijuana Bad for Health? Here’s What We Know So Far

Marijuana’s health impacts—good and bad—are coming into focus

By Jesse Greenspan

Cappi Thompson/Getty Images

With decades of legal and social opprobrium fading fast, marijuana has become an extremely popular commercial product with more than 48 million users across the U.S. Health concerns, once exaggerated, now often seem to be downplayed or overlooked. For example, pregnant patients “often tell me they had no idea there's any risk,” says University of Utah obstetrician Torri Metz, lead author of a recent paper in the Journal of the American Medical Association on cannabis and adverse pregnancy outcomes.

Fortunately, legal reforms are also gradually making it easier to study marijuana's health effects by giving U.S. scientists more access to the drug and a wider population of users to study. Although much research remains in “early stages,” the number of studies has finally been increasing, says Tiffany Sanchez, an environmental health scientist at Columbia University. As new results accumulate, they offer a long-overdue update on what science really knows about the drug.

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In addition to minor side effects that many users joke about—such as short-term memory loss—recent studies have linked marijuana to adverse health outcomes involving the lungs, heart, brain and gonads. For example, heavy marijuana consumption seems to increase the risk of clogged arteries and heart failure , and it may impact male fertility . Smoking weed likewise can lead to chronic bronchitis and other respiratory ailments (although, unlike tobacco, it hasn't been definitively tied to lung cancer). And cannabis plants hyperaccumulate metal pollutants, such as lead, which Sanchez found can enter users' bloodstreams .

Developing adolescent brains, particularly those predisposed to mental illness, may be most at risk from overconsumption. Although psychiatric effects are hotly debated , studies suggest that heavy weed use exacerbates—or may trigger— schizophrenia , psychosis and depression in youths and that it affects behavior and academic performance. “From a safety viewpoint, young people should definitely stay away from it,” says University of Ottawa psychiatrist Marco Solmi, lead author of a recent review of cannabis and health in the British Medical Journal .

24 states have legalized recreational marijuana, with 38 allowing medical use

Moreover, the drug can cross over to fetuses during pregnancy. Several studies have linked it to low birth weights , and researchers suspect it raises the likelihood of neonatal intensive care unit admissions and stillbirths . Some cannabis dispensaries have advertised their products as a cure for morning sickness, but Metz emphasizes that safer alternatives exist.

Of course, many adults use marijuana responsibly for pleasure and relaxation. Unlike with, say, opioids, there's effectively zero risk of life-threatening overdose. Plus, “people get addicted with tobacco way faster,” says Columbia University epidemiologist Silvia Martins, who studies substance use and related laws.

Cannabis, and its derivatives, also may help alleviate pain—although some researchers contend that it performs little better than a placebo . It may also decrease chemotherapy-induced nausea, calm epileptic seizures , ease the symptoms of multiple sclerosis and serve as a sleep aid .

Recent studies have hinted that the drug might slightly reduce opioid dependency rates, although this, too, is disputed . There's some evidence that weed users tend to be more empathetic , and researchers found that elderly mice get a mental boost from the drug. Still, experts caution against self-medicating: “You should ask your doctor,” Solmi says.

Some of the recent research into marijuana is more lighthearted. One study, for instance, found that, just like people, nematode worms dosed with cannabis get the munchies .

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Benefits and harms of medical cannabis: a scoping review of systematic reviews

Misty pratt.

1 Knowledge Synthesis Group, Ottawa Methods Centre, Ottawa Hospital Research Institute, The Ottawa Hospital, General Campus, 501 Smyth Road, Ottawa, Ontario K1H 8 L6 Canada

Adrienne Stevens

2 TRIBE Graduate Program, University of Split School of Medicine, Split, Croatia

Micere Thuku

Claire butler.

3 Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3A 2B4 Canada

Becky Skidmore

4 Ottawa, Canada

L. Susan Wieland

5 Center for Integrative Medicine, University of Maryland School of Medicine, Baltimore, MD USA

Mark Clemons

6 School of Epidemiology and Public Health, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8 M5 Canada

7 Division of Medical Oncology and Department of Medicine, University of Ottawa, Ottawa, Canada

Salmaan Kanji

8 Department of Pharmacy, The Ottawa Hospital, Ottawa, Canada

9 Clinical Epidemiology Program, The Ottawa Hospital Research Institute, Ottawa, Canada

Brian Hutton

Associated data.

All data generated or analyzed during this study are included in this published article (and its supplementary information files).

There has been increased interest in the role of cannabis for treating medical conditions. The availability of different cannabis-based products can make the side effects of exposure unpredictable. We sought to conduct a scoping review of systematic reviews assessing benefits and harms of cannabis-based medicines for any condition.

A protocol was followed throughout the conduct of this scoping review. A protocol-guided scoping review conduct. Searches of bibliographic databases (e.g., MEDLINE®, Embase, PsycINFO, the Cochrane Library) and gray literature were performed. Two people selected and charted data from systematic reviews. Categorizations emerged during data synthesis. The reporting of results from systematic reviews was performed at a high level appropriate for a scoping review.

After screening 1975 citations, 72 systematic reviews were included. The reviews covered many conditions, the most common being pain management. Several reviews focused on management of pain as a symptom of conditions such as multiple sclerosis (MS), injury, and cancer. After pain, the most common symptoms treated were spasticity in MS, movement disturbances, nausea/vomiting, and mental health symptoms. An assessment of review findings lends to the understanding that, although in a small number of reviews results showed a benefit for reducing pain, the analysis approach and reporting in other reviews was sub-optimal, making it difficult to know how consistent findings are when considering pain in general. Adverse effects were reported in most reviews comparing cannabis with placebo (49/59, 83%) and in 20/24 (83%) of the reviews comparing cannabis to active drugs. Minor adverse effects (e.g., drowsiness, dizziness) were common and reported in over half of the reviews. Serious harms were not as common, but were reported in 21/59 (36%) reviews that reported on adverse effects. Overall, safety data was generally reported study-by-study, with few reviews synthesizing data. Only one review was rated as high quality, while the remaining were rated of moderate ( n = 36) or low/critically low ( n = 35) quality.

Conclusions

Results from the included reviews were mixed, with most reporting an inability to draw conclusions due to inconsistent findings and a lack of rigorous evidence. Mild harms were frequently reported, and it is possible the harms of cannabis-based medicines may outweigh benefits.

Systematic review registration

The protocol for this scoping review was posted in the Open Access ( https://ruor.uottawa.ca/handle/10393/37247 ).

Interest in medical applications of marijuana ( Cannabis sativa ) has increased dramatically during the past 20 years. A 1999 report from the National Academies of Sciences, Engineering, and Medicine supported the use of marijuana in medicine, leading to a number of regulatory medical colleges providing recommendations for its prescription to patients [ 1 ]. An updated report in 2017 called for a national research agenda, improvement of research quality, improvement in data collection and surveillance efforts, and strategies for addressing barriers in advancing the cannabis agenda [ 2 ].

Proponents of medical cannabis support its use for a highly varied range of medical conditions, most notably in the fields of pain management [ 3 ] and multiple sclerosis [ 4 ]. Marijuana can be consumed by patients in a variety of ways including smoking, vaporizing, ingesting, or administering sublingually or rectally. The plant consists of more than 100 known cannabinoids, the main ones of relevance to medical applications being tetrahydrocannabinol (THC) and cannabidiol (CBD) [ 5 ]. Synthetic forms of marijuana such as dronabinol and nabilone are also available as prescriptions in the USA and Canada [ 6 ].

Over the last decade, there has been an increased interest in the use of medical cannabis products in North America. It is estimated that over 3.5 million people in the USA are legally using medical marijuana, and a total of USD$6.7 billion was spent in North America on legal marijuana in 2016 [ 7 ]. The number of Canadian residents with prescriptions to purchase medical marijuana from Health Canada–approved growers tripled from 30,537 in 2015 to near 100,000 in 2016 [ 8 ]. With the legalization of recreational-use marijuana in parts of the USA and in Canada in October 2018, the number of patients using marijuana for therapeutic purposes may become more difficult to track. The likely increase in the numbers of individuals consuming cannabis also necessitates a greater awareness of its potential benefits and harms.

Plant-based and plant-derived cannabis products are not monitored as more traditional medicines are, thereby increasing the uncertainty regarding its potential health risks to patients [ 3 ]. While synthetic forms of cannabis are available by prescription, different cannabis plants and products contain varied concentrations of THC and CBD, making the effects of exposure unpredictable [ 9 ]. While short-lasting side effects including drowsiness, loss of short-term memory, and dizziness are relatively well known and may be considered minor, other possible effects (e.g., psychosis, paranoia, anxiety, infection, withdrawal) may be more harmful to patients.

There remains a considerable degree of clinical equipoise as to the benefits and harms of marijuana use for medical purposes [ 10 – 13 ]. To understand the extent of synthesized evidence underlying this issue, we conducted a scoping review [ 14 ] of systematic reviews evaluating the benefits and/or harms of cannabis (plant-based, plant-derived, and synthetic forms) for any medical condition. We located and mapped systematic reviews to summarize research that is available for consideration for practice or policy questions in relation to medical marijuana.

A scoping review protocol was prepared and posted to the University of Ottawa Health Sciences Library’s online repository ( https://ruor.uottawa.ca/handle/10393/37247 ). We used the PRISMA for Scoping Reviews checklist to guide the reporting of this report (see Additional file 1 ) [ 15 ].

Literature search and process of study selection

An experienced medical information specialist developed and tested the search strategy using an iterative process in consultation with the review team. Another senior information specialist peer-reviewed the strategy prior to execution using the PRESS Checklist [ 16 ]. We searched seven Ovid databases: MEDLINE®, including Epub Ahead of Print and In-Process & Other Non-Indexed Citations, Embase, Allied and Complementary Medicine Database, PsycINFO, the Cochrane Database of Systematic Reviews, the Database of Abstracts of Reviews of Effects, and the Health Technology Assessment Database. The final peer-reviewed search strategy for MEDLINE was translated to the other databases (see Additional file 2 ). We performed the searches on November 3, 2017.

The search strategy incorporated controlled vocabulary (e.g., “Cannabis,” “Cannabinoids,” “Medical Marijuana”) and keywords (e.g., “marijuana,” “hashish,” “tetrahydrocannabinol”) and applied a broad systematic review filter where applicable. Vocabulary and syntax were adjusted across the databases and where possible animal-only and opinion pieces were removed, from the search results.

Gray literature searching was limited to relevant drug and mental health databases, as well as HTA (Health Technology Assessment) and systematic review databases. Searching was guided by the Canadian Agency for Drugs and Technologies in Health’s (CADTH) checklist for health-related gray literature (see Additional file 3 ). We performed searches between January and February 2018. Reference lists of overviews were searched for relevant systematic reviews, and we searched for full-text publications of abstracts or protocols.

Management of all screening was performed using Distiller SR Software ® (Evidence Partners Inc., Ottawa, Canada). Citations from the literature search were collated and de-duplicated in Reference Manager (Thomson Reuters: Reference Manager 12 [Computer Program]. New York: Thomson Reuters 2011), and then uploaded to Distiller. The review team used Distiller for Levels 1 (titles and abstracts) and 2 (full-text) screening. Pilot testing of screening questions for both levels were completed prior to implementation. All titles and abstracts were screened in duplicate by two independent reviewers (MT and MP) using the liberal accelerated method [ 17 ]. This method requires only one reviewer to assess an abstract as eligible for full-text screening, and requires two reviewers to deem the abstract irrelevant. Two independent reviewers (MT and MP) assessed full-text reports for eligibility. Disagreements during full-text screening were resolved through consensus, or by a third team member (AS). The process of review selection was summarized using a PRISMA flow diagram (Fig. ​ (Fig.1) 1 ) [ 18 ].

PRISMA-style flow diagram of the review selection process

Review selection criteria

English-language systematic reviews were included if they reported that they investigated harms and/or benefits of medical or therapeutic use of cannabis for adults and children for any indication. Definitions related to medical cannabis/marijuana are provided in Table ​ Table1. 1 . We also included synthetic cannabis products, which are prescribed medicines with specified doses of THC and CBD. Reviews of solely observational designs were included only in relation to adverse effects data, in order to focus on the most robust evidence available. We considered studies to be systematic reviews if at least one database was searched with search dates reported, at least one eligibility criterion was reported, the authors had assessed the quality of included studies, and there was a narrative or quantitative synthesis of the evidence. Reviews assessing multiple interventions (both pharmacological and complementary and alternative medicine (CAM) interventions) were included if the data for marijuana studies was reported separately. Published and unpublished guidelines were included if they conducted a systematic review encompassing the criteria listed above.

Context for the use of cannabis-related terms during the review selection process

We excluded overviews of systematic reviews, reviews in abstract form only, and review protocols. We further excluded systematic reviews focusing on recreational, accidental, acute, or general cannabis use/abuse and interventions such as synthetic cannabinoids not approved for therapeutic use (e.g., K2 or Spice).

Data collection and quality assessment

All data were collected electronically in a pre-developed form using Microsoft Excel software (Microsoft Corporation, Seattle, USA). The form was pilot tested on three included reviews by three people. One reviewer (MP or CB) independently extracted all data, and a second reviewer (MT) verified all of the items collected and checked for any omitted data. Disagreements were resolved by consensus and consultation with a third reviewer if necessary. A data extraction form with the list of included variables is provided in Additional file 4 . All collected data has also been made available in the online supplemental materials associated with this report.

Quality assessment of systematic reviews was performed using the AMSTAR-2 [ 20 ] tool. One reviewer (MP or CB) independently assessed quality, while a second reviewer (MT) verified the assessments. Disagreements were resolved by consensus and consultation with a third reviewer if necessary. The tool consists of 16 items in total, with four critical domains and 12 non-critical domains. The AMSTAR-2 tool is not intended to generate an overall score, and instead allows for an overall rating based on weaknesses in critical domains. Reviews were rated as high (no critical flaws with zero or one non-critical flaw), moderate (no critical flaws with ≥ 1 non-critical flaw), low (one critical flaw with/without non-critical weakness), or critically low (> 1 critical flaw with/without non-critical weakness) quality.

Evidence synthesis

We used a directed content analytic approach [ 21 ] with an initial deductive framework [ 22 ] that allowed flexibility for inductive analysis if refinement or development of new categorization was needed. The framework used to categorize outcome data results is outlined in Table ​ Table2. 2 . Where reviews had a mix of narrative and quantitative data, results from meta-analyses were prioritized over count data or study-by-study data. The extraction and reporting of data results was performed at a high level and did not involve an in-depth evaluation, which is appropriate for a scoping review [ 14 ]. Review authors’ conclusions and/or recommendations were extracted and reported narratively.

Outcome result categorization

Changes from the study protocol

For feasibility, we decided to limit the inclusion of systematic reviews of only observational study designs to those that addressed adverse events data. All other steps of the review were performed as planned.

Search findings

The PRISMA flow diagram describing the process of review selection is presented in Fig. ​ Fig.1. 1 . After duplicates were removed, the search identified a total of 1925 titles and abstracts, of which 47 references were located through the gray literature search. Of the total 1925 citations assessed during Level 1 screening, 1285 were deemed irrelevant. We reviewed full-text reports for the 640 reviews of potential relevance, and of these, 567 were subsequently excluded, leaving a total of 72 systematic reviews that were included; the associated data collected are provided in Additional file 5 . A listing of the reports excluded during full-text review is provided in Additional file 6 .

Characteristics of included reviews

There were 63 systematic reviews [ 4 , 19 , 23 – 83 ] and nine guidelines with systematic reviews [ 84 – 92 ]. Overall, 27 reviews were performed by researchers in Europe, 16 in the USA, 15 in Canada, eight in Australia, two in Brazil, and one each in Israel, Singapore, South Africa, and China. Funding was not reported in 29 (40%) of the reviews, and the remaining reviews received funding from non-profit or academic ( n = 20; 28%), government ( n = 14; 19%), industry ( n = 3; 4%), and mixed ( n = 1; 1%) sources. Five reviews reported that they did not receive any funding for the systematic review. Tables ​ Tables3, 3 , ​ ,4, 4 , ​ ,5, 5 , ​ ,6, 6 , ​ ,7, 7 , ​ ,8, 8 , ​ ,9, 9 , ​ ,10, 10 , ​ ,11, 11 , ​ ,12, 12 , and ​ and13 13 provide an overview of the characteristics of the 72 included systematic reviews.

Multiple sclerosis

MS multiple sclerosis, NICE National Institute for Health and Care Excellence, No . number, NR not reported, NRS numerical rating scale, QoL quality of life, RMI Rivermead Mobility Index, SBS study-by-study, VAS visual analog scale

*A colon indicates that there were separate analyses for each comparator

Movement disorders

HD Huntington’s disease, MS multiple sclerosis, NR not reported, PD Parkinson’s disease, SBS study-by-study, SCL-90R Symptoms Checklist-90 Revised, QoL quality of life, STSSS Shapiro Tourette Syndrome Severity Scale, THC tetrahydrocannabinol, TS-CGI Tourette Syndrome Clinical Global Impressions, TSSL Tourette’s Syndrome Symptom List (patient rated), VAS visual analog scale, YGTSS Yale Global Tic Severity Scale

AE : adverse effect, NICE National Institute for Health and Care Excellence, NNT numbers needed to treat, NP neuropathic pain, NR not reported, QoL quality of life, QST quantitative sensory testing, SBS study-by-study, VAS visual analog scale

*A colon indicates that there were separate analyses for each comparator; a “+” sign indicates placebo was combined with another comparator

AE adverse effect, NP neuropathic pain, NR not reported, NRS numerical rating scale, QoL quality of life, THC tetrahydrocannabinol, SIGN Scottish Intercollegiate Guidelines Network, SBS study-by-study

Rheumatic disease

AE adverse event, FM fibromyalgia, NR not reported, NRS numerical rating scale, OA osteoarthritis, RA rheumatoid arthritis, SBS study-by-study

NP neuropathic pain, NR not reported, QoL quality of life, SBS study-by-study

Mental health

PTSD posttraumatic stress disorder, SBS study-by-study

NP neuropathic pain, NR not reported, SBS study-by-study

Neurological conditions

AE adverse effect, ALS amyotrophic lateral sclerosis, CADTH Canadian Agency for Drugs and Technologies in Health, NR not reported

Various conditions

AE adverse effect, AD Alzheimer’s disease, ALS amyotrophic lateral sclerosis, CADTH Canadian Agency for Drugs and Technologies in Health, CGI-C Clinical Global Impression of Change scale, COPD Chronic Obstructive Pulmonary Disease, FIQ fibromyalgia impact questionnaire, FM fibromyalgia, HD Huntington’s disease, IBD inflammatory bowel disease, MS multiple sclerosis, NP neuropathic pain, NR not reported, PD Parkinson’s disease, PTSD posttraumatic stress disorder, RA rheumatoid arthritis, SBS study-by-study, SCI spinal cord injury

Other conditions

CADTH Canadian Agency for Drugs and Technologies in Health, IBS irritable bowel syndrome, NR not reported, QoL quality of life, SBS study-by-study, VAS visual analog scale

The reviews were published between 2000 and 2018 (median year 2014), and almost half (47%) were focused solely on medical cannabis. Four (6%) reviews covered both medical and other cannabis use (recreational and substance abuse), 19 (26%) reported multiple pharmaceutical interventions (cannabis being one), six (8%) reported various CAM interventions (cannabis being one), and nine (13%) were mixed pharmaceutical and CAM interventions (cannabis being one). Multiple databases were searched by almost all of the reviews (97%), with Medline/PubMed or Embase common to all.

Cannabis use

Figure ​ Figure2 2 illustrates the different cannabis-based interventions covered by the included reviews. Plant-based cannabis consists of whole plant products such as marijuana or hashish. Plant-derived cannabinoids are active constituents of the cannabis plant, such as tetrahydrocannabinol (THC), cannabidiol (CBD), or a combination of THC:CBD (also called nabiximols, under the brand name Sativex) [ 3 ]. Synthetic cannabinoids are manufactured rather than extracted from the plant and include drugs such as nabilone and dronabinol.

Review coverage of the various cannabis-based interventions

Twenty-seven reviews included solely interventions from plant-derived cannabinoids, 10 studied solely synthetic cannabinoids, and eight included solely studies on plant-based cannabis products. Twenty-four reviews covered a combination of different types of cannabis, and the remaining three systematic reviews did not report which type of cannabinoid was administered in the included studies.

The systematic reviews covered a wide range of conditions and illnesses, the most notable being pain management. Seventeen reviews looked at specific types of pain including neuropathic [ 31 , 42 , 62 , 69 , 85 , 90 ], chronic [ 26 , 32 , 52 , 58 , 80 ], cancer [ 84 , 87 ], non-cancer [ 41 , 68 ], and acute [ 38 ] types of pain (one review covered all types of pain) [ 65 ]. Twenty-seven reviews (38%) also focused on management of pain as a symptom of conditions such as multiple sclerosis (MS) [ 6 , 23 , 27 , 43 , 46 , 52 , 63 , 85 , 92 ], injury [ 29 , 35 , 36 , 69 ], cancer [ 37 , 43 , 65 , 88 ], inflammatory bowel disease (IBD) [ 28 ], rheumatic disease (RD) [ 49 , 51 , 73 ], diabetes [ 68 – 70 ], and HIV [ 48 , 53 , 67 ]. In Fig. ​ Fig.3, 3 , the types of illnesses addressed by the set of included reviews are graphically represented, with overlap between various conditions and pain. Some systematic reviews covered multiple diseases, and therefore the total number of conditions represented in Fig. ​ Fig.3 3 is greater than the total number of included reviews.

Conditions or symptoms across reviews that were treated with cannabis. IBD inflammatory bowel disease, MS multiple sclerosis, RD rheumatic disease

One review included a pediatric-only population, in the evaluation of marijuana for nausea and vomiting following chemotherapy [ 54 ]. Although trials in both adult and child populations were eligible for thirteen (18%) reviews, only two additional reviews included studies in children; these reviews evaluated cannabis in cancer [ 60 ] and a variety of conditions [ 25 ]. Many of the reviews ( n = 25, 35%) included only adults ≥ 18 years of age. Almost half of the reviews ( n = 33, 46%) did not report a specific population for inclusion.

Cannabis was prescribed for a wide range of medical issues. The indication for cannabis use is illustrated in Fig. ​ Fig.4. 4 . Pain management ( n = 27) was the most common indication for cannabis use. A number of reviews sought to address multiple disease symptoms ( n = 12) or explored a more holistic treatment for the disease itself ( n = 11). After pain, the most common symptoms being treated with cannabis were spasticity in MS, movement disturbances (such as dyskinesia, tics, and spasms), weight or nausea/vomiting, and mental health symptoms.

Indications for cannabis use across included reviews

Figure ​ Figure5 5 summarizes the breadth of outcomes analyzed in the included reviews. The most commonly addressed outcomes were withdrawal due to adverse effects, “other pain,” neuropathic pain, spasticity, and the global impression of the change in clinical status. Many outcomes were reported using a variety of measures across reviews. For example, spasticity was measured both objectively (using the Ashworth scale) and subjectively (using a visual analog scale [VAS] or numerical rating scale [NRS]). Similarily, outcomes for pain included VAS or NRS scales, reduction in pain, pain relief, analgesia, pain intensity, and patient assessment of change in pain.

Quality of the systematic reviews

Quality assessments of the included reviews based upon AMSTAR-2 are detailed in Additional file 7 and Additional file 8 . Only one review was rated as high quality [ 45 ]. All other reviews were deemed to be of moderate ( n = 36) or low/critically low ( n = 35) methodological quality. Assessments for the domains deemed of critical importance for determining quality ratings are described below.

Only 20% of reviews used a comprehensive search strategy; another 47% were given a partial score because they had not searched the reference lists of the included reviews, trial registries, gray literature, and/or the search date was older than 2 years. The remaining reviews did not report a comprehensive search strategy.

Over half of the reviews (51%) used a satisfactory technique for assessing risk of bias (ROB) of the individual included studies, while 35% were partially satisfactory because they had not reported whether allocation sequence was truly random and/or they had not assessed selective reporting. The remaining reviews did not report a satisfactory technique for assessing ROB.

Most reviews (71%) could not be assessed for an appropriate statistical method for combining results in a meta-analysis, as they synthesized study data narratively. Approximately 19% of reviews used an appropriate meta-analytical approach, leaving 10% that used inappropriate methods.

The final critical domain for the AMSTAR-2 determines whether review authors accounted for ROB in individual studies when discussing or interpreting the results of the review. The majority of reviews (83%) did so in some capacity.

Mapping results of included systematic reviews

We mapped reviews according to authors’ comparisons, the conditions or symptoms they were evaluating, and the categorization of the results (see Table ​ Table2). 2 ). In some cases, reviews contributed to more than one comparison (e.g., cannabis versus placebo or active drug). As pain was the most commonly addressed outcome, we mapped this outcome separately from all other endpoints. This information is shown for all reviews and then restricted to reviews of moderate-to-high quality (as determined using the AMSTAR-2 criteria): cannabis versus placebo (Figs. ​ (Figs.6 6 and ​ and7), 7 ), cannabis versus active drugs (Figs. ​ (Figs.8 8 and ​ and9), 9 ), cannabis versus a combination of placebo and active drug (Figs. ​ (Figs.10 10 and ​ and11), 11 ), one cannabis formulation versus other (Figs. ​ (Figs.12 12 and ​ and13), 13 ), and cannabis analyzed against all other comparators (Fig. ​ (Fig.14). 14 ). Details on how to read the figures are provided in the corresponding figure legends. The median number of included studies across reviews was four, and ranged from one to seventy-nine (not shown in figures).

Cannabis vs. placebo. Authors’ presentations of the findings were mapped using the categorization shown in Table ​ Table2. 2 . According to the reviews’ intended scope for the condition being treated, outcomes were mapped into “pain,” “non-pain outcomes,” and “adverse events.” For each condition and outcome pair (i.e., each row in the grid), the number of reviews reporting findings is shown according to the results categorization. For pain, reviews numbered in different categories signal discordant findings across those reviews. For non-pain outcomes, reviews presenting findings in the different categories would signal different results for different outcomes, as well as discordant findings within and across reviews. Adverse events are grouped as a whole and “favors intervention” would be interpreted as a decrease in events with cannabis when compared with the control group. Favors int = favors intervention; Favors Ctrl = favors control; Not stat sig = not statistically significant

Cannabis vs. placebo, high and moderate quality reviews. Authors’ presentations of the findings were mapped using the categorizations shown in Table ​ Table2. 2 . According to the reviews’ intended scope for the condition being treated, outcomes were mapped into “pain,” “non-pain outcomes,” and “adverse events.” For each condition and outcome pair (i.e., each row in the grid), the number of reviews reporting findings is shown according to the results categorization. For pain, reviews numbered in different categories signal discordant findings across those reviews. For non-pain outcomes, reviews presenting findings in the different categories would signal different results for different outcomes, as well as discordant findings within and across reviews. Adverse events are grouped as a whole and “favors intervention” would be interpreted as a decrease in events with cannabis when compared with the control group. Favors int = favors intervention; Favors Ctrl = favors control; Not stat sig = not statistically significant

Cannabis vs. active drugs. Authors’ presentations of the findings were mapped using the categorizations shown in Table ​ Table2. 2 . According to the reviews’ intended scope for the condition being treated, outcomes were mapped into “pain,” “non-pain outcomes,” and “adverse events.” For each condition and outcome pair (i.e., each row in the grid), the number of reviews reporting findings is shown according to the results categorization. For pain, reviews numbered in different categories signal discordant findings across those reviews. For non-pain outcomes, reviews presenting findings in the different categories would signal different results for different outcomes, as well as discordant findings within and across reviews. Adverse events are grouped as a whole and “favors intervention” would be interpreted as a decrease in events with cannabis when compared with the control group. Favors int = favors intervention; Favors Ctrl = favors control; Not stat sig = not statistically significant

Cannabis vs. active drugs, high and moderate quality reviews. Authors’ presentations of the findings were mapped using the categorizations shown in Table ​ Table2. 2 . According to the reviews’ intended scope for the condition being treated, outcomes were mapped into “pain,” “non-pain outcomes,” and “adverse events.” For each condition and outcome pair (i.e., each row in the grid), the number of reviews reporting findings is shown according to the results categorization. For pain, reviews numbered in different categories signal discordant findings across those reviews. For non-pain outcomes, reviews presenting findings in the different categories would signal different results for different outcomes, as well as discordant findings within and across reviews. Adverse events are grouped as a whole and “favors intervention” would be interpreted as a decrease in events with cannabis when compared with the control group. Favors int = favors intervention; Favors Ctrl = favors control; Not stat sig = not statistically significant

Cannabis vs. placebo + active drug. Authors’ presentations of the findings were mapped using the categorizations shown in Table ​ Table2. 2 . According to the reviews’ intended scope for the condition being treated, outcomes were mapped into “pain,” “non-pain outcomes,” and “adverse events.” For each condition and outcome pair (i.e., each row in the grid), the number of reviews reporting findings is shown according to the results categorization. For pain, reviews numbered in different categories signal discordant findings across those reviews. For non-pain outcomes, reviews presenting findings in the different categories would signal different results for different outcomes, as well as discordant findings within and across reviews. Adverse events are grouped as a whole and “favors intervention” would be interpreted as a decrease in events with cannabis when compared with the control group. Favors int = favors intervention; Favors Ctrl = favors control; Not stat sig = not statistically significant

Cannabis vs. placebo + active drug, high and moderate quality reviews. Authors’ presentations of the findings were mapped using the categorizations shown in Table ​ Table2. 2 . According to the reviews’ intended scope for the condition being treated, outcomes were mapped into “pain,” “non-pain outcomes,” and “adverse events.” For each condition and outcome pair (i.e., each row in the grid), the number of reviews reporting findings is shown according to the results categorization. For pain, reviews numbered in different categories signal discordant findings across those reviews. For non-pain outcomes, reviews presenting findings in the different categories would signal different results for different outcomes, as well as discordant findings within and across reviews. Adverse events are grouped as a whole and “favors intervention” would be interpreted as a decrease in events with cannabis when compared with the control group. Favors int = favors intervention; Favors Ctrl = favors control; Not stat sig = not statistically significant

One cannabis formulation vs. other. Authors’ presentations of the findings were mapped using the categorizations shown in Table ​ Table2. 2 . According to the reviews’ intended scope for the condition being treated, outcomes were mapped into “pain,” “non-pain outcomes,” and “adverse events.” For each condition and outcome pair (i.e., each row in the grid), the number of reviews reporting findings is shown according to the results categorization. For pain, reviews numbered in different categories signal discordant findings across those reviews. For non-pain outcomes, reviews presenting findings in the different categories would signal different results for different outcomes, as well as discordant findings within and across reviews. Adverse events are grouped as a whole and “favors intervention” would be interpreted as a decrease in events with cannabis when compared with the control group. Favors int = favors intervention; Favors Ctrl = favors control; Not stat sig = not statistically significant

One cannabis formulation vs. other, high and moderate quality reviews. Authors’ presentations of the findings were mapped using the categorizations shown in Table ​ Table2. 2 . According to the reviews’ intended scope for the condition being treated, outcomes were mapped into “pain,” “non-pain outcomes,” and “adverse events.” For each condition and outcome pair (i.e., each row in the grid), the number of reviews reporting findings is shown according to the results categorization. For pain, reviews numbered in different categories signal discordant findings across those reviews. For non-pain outcomes, reviews presenting findings in the different categories would signal different results for different outcomes, as well as discordant findings within and across reviews. Adverse events are grouped as a whole and “favors intervention” would be interpreted as a decrease in events with cannabis when compared with the control group. Favors int = favors intervention; Favors Ctrl = favors control; Not stat sig = not statistically significant

Cannabis vs. all comparators combined. Authors’ presentations of the findings were mapped using the categorizations shown in Table ​ Table2. 2 . According to the reviews’ intended scope for the condition being treated, outcomes were mapped into “pain,” “non-pain outcomes,” and “adverse events.” For each condition and outcome pair (i.e., each row in the grid), the number of reviews reporting findings is shown according to the results categorization. For pain, reviews numbered in different categories signal discordant findings across those reviews. For non-pain outcomes, reviews presenting findings in the different categories would signal different results for different outcomes, as well as discordant findings within and across reviews. Adverse events are grouped as a whole and “favors intervention” would be interpreted as a decrease in events with cannabis when compared with the control group. Favors int = favors intervention; Favors Ctrl = favors control; Not stat sig = not statistically significant

Cannabis versus placebo

Most reviews (59/72, 82%) compared cannabis with placebo. Of these reviews, 34 (58%) addressed pain outcomes and 47 (80%) addressed non-pain outcomes, with most outcomes addressed by three reviews or fewer (Fig. ​ (Fig.6). 6 ). Some reviews had a mix of quantitative syntheses and study-by-study data reported (13/59, 22%), while another group of reviews (14/59, 24%) only reported results study-by-study. Overall, 24% (14/59) of the cannabis versus placebo reviews had only one included study.

• i. Reviews focused on addressing pain across conditions. In most cases, findings were discordant across reviews for the pain outcomes measured. For chronic non-cancer pain, however, two reviews favored cannabis over placebo for decreasing pain. One review assessing acute pain for postoperative pain relief found no difference between various cannabinoid medications and placebo. The distribution of findings was similar when restricting to moderate-to-high-quality reviews.
• ii. Reviews focused on treating a condition or family of related conditions . Various results were observed for pain. For MS and HIV/AIDS, one review each reported quantitative results favoring cannabis for decreased pain but with other reviews reporting results study-by-study, it is difficult to know, broadly, how consistent those findings are. For cancer, two reviews reported results favoring cannabis for decreased pain. For rheumatic disease, findings are discordant between two reviews, and another two reviews reported results study-by-study. One review that included studies of MS or paraplegia found no difference in pain between groups. For treating injury, one review showed that the placebo group had less pain and one review reported data study-by-study. No reviews addressed pain in movement disorders, neurological conditions, and IBD.

For those reviews assessing pain as part of a focus on treating a range of conditions, two showed cannabis reduced pain [ 43 , 52 ], but one showed mixed results depending on how pain was measured [ 43 ]. These reviews covered several different conditions, including injury, chronic pain, rheumatoid arthritis, osteoarthritis, fibromyalgia, HIV/AIDS, cancer, and MS or paraplegia.

When restricting to moderate-to-high-quality reviews, only one review each in multiple sclerosis and HIV/AIDS with a study-by-study analysis on pain remained. One review on cancer favored cannabis for pain reduction. Findings remained the same for MS or paraplegia and rheumatic disease. No review for injury and paint outcomes was of higher quality.

• 2. Non-pain outcomes

The types of non-pain outcomes included in the reviews varied by condition/illness. The most commonly reported outcomes (see Fig. ​ Fig.5 5 for overall outcomes) when comparing cannabis to placebo included muscle- or movement-related outcomes ( n = 20), quality of life ( n = 14), and sleep outcomes ( n = 10).

There was no consistent pattern for non-pain outcomes either within or across medical conditions. Many ( n = 24, 33%) reviews assessing non-pain outcomes reported the results of those analyses study-by-study. Conflicting results are observed in some cases due to the use of different measures, such as different ways of quantifying spasticity in patients with multiple sclerosis [ 56 , 91 ]. One review each addressing neurological conditions [ 50 ] (outcome: muscle cramps) and MS/paraplegia [ 27 ] (outcomes: spasticity, spasm, cognitive function, daily activities, motricity, and bladder function) showed no difference between groups.

• 3. Adverse effects

Adverse effects were reported in most reviews comparing cannabis with placebo (49/59, 83%). Most adverse events were reported study-by-study, with few reviews ( n = 16/59, 27%) conducting a narrative or quantitative synthesis. Serious adverse effects were reported in 21/59 (36%) reviews, and minor adverse effects were reported in 30/59 (51%) reviews. The remaining reviews did not define the difference between serious and minor adverse events. The most commonly reported serious adverse events included psychotic symptoms ( n = 6), severe dysphoric reactions ( n = 3), seizure ( n = 3), and urinary tract infection ( n = 2). The most commonly reported minor adverse events included somnolence/drowsiness ( n = 28), dizziness ( n = 27), dry mouth ( n = 20), and nausea ( n = 18). Many reviews ( n = 37/59, 63%) comparing cannabis to placebo reported both neurocognitive and non-cognitive adverse effects. Withdrawals due to adverse events were reported in 22 (37%) reviews.

Of the moderate-/high-quality reviews, adverse effect analyses were reported in reviews on pain, multiple sclerosis, cancer, HIV/AIDS, movement disorders, rheumatic disease, and several other conditions. Two reviews on pain showed fewer adverse events with cannabis for euphoria, events linked to alternations in perception, motor function, and cognitive function, withdrawal due to adverse events, sleep, and dizziness or vertigo [ 58 , 90 ]. One review on MS showed that there was no statistically significant difference between cannabis and placebo for adverse effects such as nausea, weakness, somnolence, and fatigue [ 91 ], while another review on MS/paraplegia reported fewer events in the placebo group for dizziness, somnolence, nausea, and dry mouth [ 27 ]. Within cancer reviews, one review found no statistically significant difference between cannabis and placebo for dysphoria or sedation but reported fewer events with placebo for “feeling high,” and fewer events with cannabis for withdrawal due to adverse effects [ 40 ]. In rheumatic disease, one review reported fewer total adverse events with cannabis and found no statistically significant difference between cannabis and placebo for withdrawal due to adverse events [ 51 ].

Cannabis versus other drugs

Relatively fewer reviews compared cannabis with active drugs ( n = 23/72, 32%) (Fig. ​ (Fig.8). 8 ). Many of the reviews did not synthesize studies quantitatively, and results were reported study-by-study. The most common conditions in reviews comparing cannabis to active drugs were pain, cancer, and rheumatic disease. Comparators included ibuprofen, codeine, diphenhydramine, amitriptyline, secobarbital, prochlorperazine, domperidone, metoclopramide, amisulpride, neuroleptics, isoproterenol, megestrol acetate, pregabalin, gabapentin, and opioids.

• i. Reviews focused on addressing pain across conditions. When comparing across reviews, a mix of results are observed (see Fig. ​ Fig.8), 8 ), and some were reported study-by-study. One review found no statistically significant difference between cannabinoids and codeine for nociceptive pain, postoperative pain, and cancer pain [ 65 ]. Another review favored “other drugs” (amitriptyline and pregabalin) over cannabinoids for neuropathic pain [ 90 ]. The distribution of findings was similar when restricting to moderate-to-high-quality reviews.
• ii. Reviews focused on treating a condition or family of related conditions. One review on cancer compared cannabinoids and codeine or secobarbital and reported pain results study-by-study. Another review on fibromyalgia comparing synthetic cannabinoids with amitriptyline also reported pain data study-by-study [ 39 ].
• Non-pain outcomes

Two reviews on cancer favored cannabinoids over active drugs (prochlorperazine, domperidone, metoclopramide, and neuroleptics) for patient preference and anti-emetic efficacy [ 40 , 60 ]. Non-pain outcomes were reported study-by-study for the outcome of sleep in neuropathic pain [ 90 ] and rheumatic disease [ 39 , 49 ]. In a review covering various conditions (pain, MS, anorexia, cancer, and immune deficiency), results were unclear or indeterminate for subjective measures of sleep [ 46 ].

Adverse effects were reported in 20/24 (83%) of the reviews comparing cannabis to active drugs, and only 6/20 (30%) reported a narrative or quantitative synthesis. Many reviews that reported narrative data did not specify whether adverse effects could be attributed to a placebo or active drug comparator.

Of the moderate-to-high-quality reviews, two pain reviews found no statistically significant difference for cannabis compared to codeine or amitriptyline for withdrawals due to adverse events [ 65 , 90 ]. Results from one cancer review were mixed, with fewer adverse events for cannabis (compared to prochlorperazine, domperidone, or metoclopramide) or no difference between groups, depending on the type of subgroup analysis that was conducted [ 40 ].

Cannabis + active drugs versus placebo + active drugs

Two reviews compared cannabis with placebo cannabis in combination with an active drug (opioids and gabapentin) (Figs. ​ (Figs.10 10 and ​ and11). 11 ). Both were scored to be of moderate quality. Although one review showed that cannabis plus opioids decreased chronic pain [ 80 ], another review on pain in MS included only a single study [ 81 ], precluding the ability to determine concordance of results. Cannabis displayed varied effects on non-pain outcomes, including superiority of placebo over cannabis for some outcomes. One review reported withdrawal due to adverse events study-by-study and also reported that side effects such as nausea, drowsiness, and dizziness were more frequent with higher doses of cannabinoids (data from two included studies) [ 80 ].

Cannabis versus other cannabis comparisons

Six (8%) reviews compared different cannabis formulations or doses (Figs. ​ (Figs.12 12 and ​ and13). 13 ). Almost all were reported as study-by-study results, with two reviews including only one RCT. One review for PTSD found only observational data [ 33 ] and another review on anxiety and depression combined data from one RCT with cross-sectional study data [ 19 ]. A single review on MS reported a narrative synthesis that found a benefit for spasticity. However, it was unclear if the comparator was placebo or THC alone [ 56 ]. Four reviews reported adverse effects study-by-study, with a single review comparing side effects from different dosages; in this review, combined extracts of THC and CBD were better tolerated than extracts of THC alone [ 56 ].

Cannabis versus all comparators

One review combined all comparators for the evaluation (Fig. ​ (Fig.14). 14 ). The review (combining non-users, placebo and ibuprofen) covered a range of medical conditions and was rated as low quality [ 30 ]. No adverse effects were evaluated for this comparison.

Mapping the use of quality assessment and frameworks to interpret the strength of evidence

Although 83% of reviews incorporated risk of bias assessments in their interpretation of the evidence, only 11 (15%) reviews used a framework such as GRADE to evaluate important domains other than risk of bias that would inform the strength of the evidence.

Mapping authors’ conclusions or recommendations

Most reviews (43/72 60%) indicated an inability to draw conclusions, whether due to uncertainty, inconsistent findings, lack of (high quality) evidence, or focusing their conclusion statement on the need for more research. Almost 15% of reviews (10/72) reported recommendations or conclusions that included some uncertainty. One review (1%) provided a statement of the extent of the strength of the evidence, which differed according to outcome.

Eleven reviews provided clearer conclusions (14%). Four indicated that cannabis was not effective or not cost-effective compared to placebo in relation to multiple sclerosis, acute pain, cancer, and injury. Three reviews addressing various conditions provided varying conclusions: one stated cannabis was not effective, one indicated it was modestly safe and effective, and one concluded that cannabis was safe and efficacious as short-term treatment; all reviews were of low quality. The three remaining reviews stated moderate or modest effects for improving chronic pain, compared with placebo or other analgesia; two of those reviews were of medium AMSTAR-2 quality, and one used the GRADE framework for interpreting the strength of the evidence.

The eight remaining included reviews (11%) did not provide a clear conclusion statement or reported only limitations.

Mapping authors’ limitations of the research

Several of the reviews indicated that few studies, small sample sizes, short duration of treatment, and issues related to outcomes (e.g., definition, timing, and types) were drawbacks to the literature. Some reviews noted methodological issues with and heterogeneity among studies as limitations. A few authors stated that restricting eligibility to randomized trials, English-language studies, or full publications may have affected their review results.

With the increasing use of medical cannabis, an understanding of the landscape of available evidence syntheses is needed to support evidence-informed decision-making, policy development, and to inform a research agenda. In this scoping review, we identified 72 systematic reviews evaluating medical cannabis for a range of conditions and illnesses. Half of the reviews were evaluated as being of moderate quality, with only one review scoring high on the AMSTAR-2 assessment tool.

There was disparity in the reported results across reviews, including non-synthesized (study-by-study) data, and many were unable to provide a definitive statement regarding the effectiveness of cannabis (as measured by pain reduction or other relevant outcomes), nor the extent of increased side effects and harms. This is consistent with the limitations declared in general across reviews, such as the small numbers of relevant studies, small sample sizes of individual studies, and methodological weaknesses of available studies. This common theme in review conclusions suggests that while systematic reviews may have been conducted with moderate or high methodological quality, the strength of their conclusions are driven by the availability and quality of the relevant underlying evidence, which was often found to be limited.

Relatively fewer reviews addressed adverse effects associated with cannabis, except to narratively summarize study level data. Although information was provided for placebo-controlled comparisons, none of the comparative effectiveness reviews quantitatively assessed adverse effects data. For the placebo-controlled data, although the majority of adverse effects were mild, the number of reviews reporting serious adverse effects such as psychotic symptoms [ 25 , 42 ] and suicidal ideation [ 68 , 85 ] warrants caution.

A mix of reviews supporting and not supporting the use of cannabis, according to authors’ conclusions, was identified. Readers may wish to consider the quality of the reviews, the use of differing quality assessment tools, additional considerations covered by the GRADE framework, and the potential for spin as possible reasons for these inconsistencies. It is also possible that cannabis has differing effects depending on its type (e.g., synthetic), dose, indication, the type of pain being evaluated (e.g., neuropathic), and the tools used for outcome assessment, which can be dependent on variations in condition. Of potential interest to readers may be a closer examination of the reviews evaluating chronic pain, in order to locate the source(s) of discordance. For example, one review was deemed of moderate quality, used the GRADE framework, and rated the quality of evidence for the effectiveness of cannabis for reducing neuropathic pain as moderate, suggesting that further investigation of cannabis for neuropathic pain may be warranted [ 80 ]. The exploration aspects outlined in this paragraph are beyond the purview of scoping review methodology; a detailed assessment of the reviews, including determining the overlap of included studies among similar reviews, potential reasons for the observed discordance of findings, what re-analysis of study-by-study analyses would yield, and an undertaking of missing GRADE assessments would fall outside the bounds of a scoping review and require the use of overview methodology [ 14 ].

Our findings are consistent with a recently published summary of cannabis-based medicines for chronic pain management [ 3 ]. This report found inconsistent results in systematic reviews of cannabis-based medicines compared to placebo for chronic neuropathic pain, pain management in rheumatic diseases and painful spasms in MS. The authors also concluded that cannabis was not superior to placebo in reducing cancer pain. Four out of eight included reviews scored high on the original AMSTAR tool. The variations between the two tools can be attributed to the differences in our overall assessments. Lastly, the summary report included two reviews that were not located in our original search due to language [ 93 ] and the full-text [ 94 ] of an abstract [ 95 ] that was not located in our search.

This scoping review has identified a plethora of synthesized evidence in relation to medical cannabis. For some conditions, the extent of review replication may be wasteful. Many reviews have stated that additional trials of methodologically robust design and, where possible, of sufficient sample size for precision, are needed to add to the evidence base. This undertaking may require the coordination of multi-center studies to ensure adequate power. Future trials may also help to elucidate the effect of cannabis on different outcomes.

Given authors’ reporting of issues in relation to outcomes, future prospective trials should be guided by a standardized, “core” set of outcomes to strive for consistency across studies and ensure relevance to patient-centered care. Development of those core outcomes should be developed using the Core Outcome Measures in Effectiveness Trials (COMET) methodology [ 96 ], and further consideration will need to be made in relation to what outcomes may be common across all cannabis research and which outcomes are condition-specific. With maturity of the evidence base, future systematic reviews should seek and include non-journal-published (gray literature) reports and ideally evaluate any non-English-language papers; authors should also adequately assess risk of bias and undertake appropriate syntheses of the literature.

The strengths of this scoping review include the use of an a priori protocol, peer-reviewed search strategies, a comprehensive search for reviews, and consideration of observational designs for adverse effects data. For feasibility, we restricted to English-language reviews, and it is unknown how many of the 39 reviews in other languages that we screened would have met our eligibility criteria. The decision to limit the inclusion of reviews of observational data to adverse effects data was made during the process of full-text screening and for pragmatic reasons. We also did not consider a search of the PROSPERO database for ongoing systematic reviews; however, in preparing this report, we performed a search and found that any completed reviews were already considered for eligibility or were not available at the time of our literature search. When charting results, we took a broad perspective, which may be different than if these reviews were more formally assessed during an overview of systematic reviews.

Cannabis-based medicine is a rapidly emerging field of study, with implications for both healthcare practitioners and patients. This scoping review is intended to map and collate evidence on the harms and benefits of medical cannabis. Many reviews were unable to provide firm conclusions on the effectiveness of medical cannabis, and results of reviews were mixed. Mild adverse effects were frequently but inconsistently reported, and it is possible that harms may outweigh benefits. Evidence from longer-term, adequately powered, and methodologically sound RCTs exploring different types of cannabis-based medicines is required for conclusive recommendations.

Supplementary information

Acknowledgements.

Not applicable.

Abbreviations

Authors’ contributions.

MP, AS, and BH drafted the initial version of the report. BS designed and implemented the literature search. MP, MT, and CB contributed to review of abstracts and full texts as well as data collection. MP, AS, and BH were responsible for analyses. All authors (MP, AS, MT, CB, BS, SW, MC, SK, BH) contributed to interpretation of findings and revision of drafts and approved the final version of the manuscript.

Research reported in this publication was supported by the National Center for Complementary and Integrative Health of the National Institutes of Health under award number R24AT001293. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Availability of data and materials

Ethics approval and consent to participate, consent for publication, competing interests.

BH has previously received honoraria from Cornerstone Research Group for provision of methodologic advice related to the conduct of systematic reviews and meta-analysis. All other authors declare that they have no conflicts of interest.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Contributor Information

Misty Pratt, Email: ac.irho@ttarpim .

Adrienne Stevens, Email: ac.irho@snevetsda .

Micere Thuku, Email: ac.irho@ukuhtm .

Claire Butler, Email: ac.irho@reltublc .

Becky Skidmore, Email: moc.sregor@eromdiksb .

L. Susan Wieland, Email: moc.liamg@dnaleiwsl .

Mark Clemons, Email: ac.hot@snomelcm .

Salmaan Kanji, Email: ac.hot@ijnaks .

Brian Hutton, Email: ac.irho@nottuhb .

Supplementary information accompanies this paper at 10.1186/s13643-019-1243-x.

Marijuana and Your Health: What 20 Years of Research Reveals

People who drive under the influence of marijuana double their risk of being in a car crash, and about one in 10 daily marijuana users becomes dependent on the drug, according to a new review.

Marijuana use has become increasingly prevalent over the years, and the review of marijuana studies summarizes what researchers have learned about the drug's effects on human health and general well-being over the past two decades.

In the review, author Wayne Hall, a professor and director of the Center for Youth Substance Abuse Research at the University of Queensland in Australia, examined scientific evidence on marijuana's health effects between 1993 and 2013.

He found that adolescents who use cannabis regularly are about twice as likely as their nonuser peers to drop out of school, as well as experience cognitive impairment and psychoses as adults. Moreover, studies have also linked regular cannabis use in adolescence with the use of other illicit drugs, according to the review, published today (Oct. 6) in the journal Addiction.

Researchers in the studies still debated whether regular marijuana use might actually lead to the use of other drugs, Hall wrote in the study. However, he pointed to longer-term studies and studies of twins in which one used marijuana and the other did not as particularly strong evidence that regular cannabis use may lead to the use of other illicit drugs. [ Marijuana vs. Alcohol: Which Is Worse for Your Health? ]

The risk of a person suffering a fatal overdose from marijuana is "extremely small," and there are no reports of fatal overdoses in the scientific literature, according to the review. However, there have been case reports of deaths from heart problems in seemingly otherwise healthy young men after they smoked marijuana, the report said.

"The perception that cannabis is a safe drug is a mistaken reaction to a past history of exaggeration of its health risks," Hall told Live Science.

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However, he added that marijuana "is not as harmful as other illicit drugs such as amphetamine, cocaine and heroin, with which it is classified under the law in many countries, including the USA."

The risks of using marijuana

Marijuana use carries some of the same risks as alcohol use, such as an increased risk of accidents, dependence and psychosis, he said.

It's likely that middle-age people who smoke marijuana regularly are at an increased risk of experiencing a heart attack , according to the report. However, the drug's "effects on respiratory function and respiratory cancer remain unclear, because most cannabis smokers have smoked or still smoke tobacco," Hall wrote in the review.

Regular cannabis users also double their risk of experiencing psychotic symptoms and disorders such as disordered thinking, hallucinations and delusions — from about seven in 1,000 cases among nonusers to 14 in 1,000 among regular marijuana users, the review said. And, in a study of more than 50,000 young men in Sweden, those who had used marijuana 10 or more times by age 18 were about two times more likely to be diagnosed with schizophrenia within the next 15 years than those who had not used the drug.

Critics argue that other variables besides marijuana use may be at work in the increased risk of mental health problems, and that it's possible that people with mental health problems are more likely to use marijuana to begin with, Hall wrote in the review.

However, other studies have since attempted to sort out the findings, he wrote, citing a 27-year follow-up of the Swedish cohort, in which researchers found "a dose–response relationship between frequency of cannabis use at age 18 and risk of schizophrenia during the whole follow-up period."

In the same study, the investigators estimated that 13 percent of schizophrenia cases diagnosed in the study "could be averted if all cannabis use had been prevented in the cohort," Hall reported.

As for the effects of cannabis use in pregnant women, the drug may slightly reduce the birth weight of the baby, according to the review.

The effects of euphoria that cannabis users seek from the drug come primarily from its psychoactive ingredient, called delta-9-tetrahydrocannabinol, better known as THC , Hall wrote in the review. During the past 30 years, the THC content of marijuana in the United States has jumped from less than 2 percent in 1980 to 8.5 percent in 2006.

The THC content of the drug has also likely increased in other developed countries, Hall wrote in the report.

It is not clear, however, whether increased THC content may have an effect on users' health, the report said. [ The Drug Talk: 7 New Tips for Today's Parents ]

Some argue that there would be no increase in harm, if users adjusted their doses of the drug and used less of the more potent cannabis products to get the same psychological effects they seek, Hall said.

However, "the limited evidence suggests that users do not completely adjust dose for potency, and so probably get larger doses of THC than used to be the case," Hall said.

Studies on the use of alcohol — and, to a lesser extent, other drugs such as opioids — have also shown that more potent forms of these substances increase users' level of intoxication, as well as their risk of accidents and developing dependence, he added.

Follow Agata Blaszczak-Boxe on  Twitter .   Follow Live Science @livescience , Facebook   & Google+ . Originally published on Live Science .

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Cannabis (Marijuana) and Cannabinoids: What You Need To Know

.header_greentext{color:green!important;font-size:24px!important;font-weight:500!important;}.header_bluetext{color:blue!important;font-size:18px!important;font-weight:500!important;}.header_redtext{color:red!important;font-size:28px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;font-size:28px!important;font-weight:500!important;}.header_purpletext{color:purple!important;font-size:31px!important;font-weight:500!important;}.header_yellowtext{color:yellow!important;font-size:20px!important;font-weight:500!important;}.header_blacktext{color:black!important;font-size:22px!important;font-weight:500!important;}.header_whitetext{color:white!important;font-size:22px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;}.Green_Header{color:green!important;font-size:24px!important;font-weight:500!important;}.Blue_Header{color:blue!important;font-size:18px!important;font-weight:500!important;}.Red_Header{color:red!important;font-size:28px!important;font-weight:500!important;}.Purple_Header{color:purple!important;font-size:31px!important;font-weight:500!important;}.Yellow_Header{color:yellow!important;font-size:20px!important;font-weight:500!important;}.Black_Header{color:black!important;font-size:22px!important;font-weight:500!important;}.White_Header{color:white!important;font-size:22px!important;font-weight:500!important;} Is marijuana the same thing as cannabis?

People often use the words “cannabis” and “marijuana” interchangeably, but they don’t mean exactly the same thing.

The word “cannabis” refers to all products derived from the plant Cannabis sativa .

• The cannabis plant contains about 540 chemical substances.
• The word “marijuana” refers to parts of or products from the plant Cannabis sativa that contain substantial amounts of tetrahydrocannabinol (THC). THC is the substance that’s primarily responsible for the effects of marijuana on a person’s mental state. Some cannabis plants contain very little THC. Under U.S. law, these plants are considered “industrial hemp” rather than marijuana.

Throughout the rest of this fact sheet, we use the term “cannabis” to refer to the plant Cannabis sativa .

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Cannabinoids are a group of substances found in the cannabis plant.

.header_greentext{color:green!important;font-size:24px!important;font-weight:500!important;}.header_bluetext{color:blue!important;font-size:18px!important;font-weight:500!important;}.header_redtext{color:red!important;font-size:28px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;font-size:28px!important;font-weight:500!important;}.header_purpletext{color:purple!important;font-size:31px!important;font-weight:500!important;}.header_yellowtext{color:yellow!important;font-size:20px!important;font-weight:500!important;}.header_blacktext{color:black!important;font-size:22px!important;font-weight:500!important;}.header_whitetext{color:white!important;font-size:22px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;}.Green_Header{color:green!important;font-size:24px!important;font-weight:500!important;}.Blue_Header{color:blue!important;font-size:18px!important;font-weight:500!important;}.Red_Header{color:red!important;font-size:28px!important;font-weight:500!important;}.Purple_Header{color:purple!important;font-size:31px!important;font-weight:500!important;}.Yellow_Header{color:yellow!important;font-size:20px!important;font-weight:500!important;}.Black_Header{color:black!important;font-size:22px!important;font-weight:500!important;}.White_Header{color:white!important;font-size:22px!important;font-weight:500!important;} What are the main cannabinoids?

The main cannabinoids are THC and cannabidiol (CBD).

.header_greentext{color:green!important;font-size:24px!important;font-weight:500!important;}.header_bluetext{color:blue!important;font-size:18px!important;font-weight:500!important;}.header_redtext{color:red!important;font-size:28px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;font-size:28px!important;font-weight:500!important;}.header_purpletext{color:purple!important;font-size:31px!important;font-weight:500!important;}.header_yellowtext{color:yellow!important;font-size:20px!important;font-weight:500!important;}.header_blacktext{color:black!important;font-size:22px!important;font-weight:500!important;}.header_whitetext{color:white!important;font-size:22px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;}.Green_Header{color:green!important;font-size:24px!important;font-weight:500!important;}.Blue_Header{color:blue!important;font-size:18px!important;font-weight:500!important;}.Red_Header{color:red!important;font-size:28px!important;font-weight:500!important;}.Purple_Header{color:purple!important;font-size:31px!important;font-weight:500!important;}.Yellow_Header{color:yellow!important;font-size:20px!important;font-weight:500!important;}.Black_Header{color:black!important;font-size:22px!important;font-weight:500!important;}.White_Header{color:white!important;font-size:22px!important;font-weight:500!important;} How many cannabinoids are there?

Besides THC and CBD, more than 100 other cannabinoids have been identified.

.header_greentext{color:green!important;font-size:24px!important;font-weight:500!important;}.header_bluetext{color:blue!important;font-size:18px!important;font-weight:500!important;}.header_redtext{color:red!important;font-size:28px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;font-size:28px!important;font-weight:500!important;}.header_purpletext{color:purple!important;font-size:31px!important;font-weight:500!important;}.header_yellowtext{color:yellow!important;font-size:20px!important;font-weight:500!important;}.header_blacktext{color:black!important;font-size:22px!important;font-weight:500!important;}.header_whitetext{color:white!important;font-size:22px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;}.Green_Header{color:green!important;font-size:24px!important;font-weight:500!important;}.Blue_Header{color:blue!important;font-size:18px!important;font-weight:500!important;}.Red_Header{color:red!important;font-size:28px!important;font-weight:500!important;}.Purple_Header{color:purple!important;font-size:31px!important;font-weight:500!important;}.Yellow_Header{color:yellow!important;font-size:20px!important;font-weight:500!important;}.Black_Header{color:black!important;font-size:22px!important;font-weight:500!important;}.White_Header{color:white!important;font-size:22px!important;font-weight:500!important;} Has the U.S. Food and Drug Administration (FDA) approved cannabis or cannabinoids for medical use?

The FDA has not approved the cannabis plant for any medical use. However, the FDA has approved several drugs that contain individual cannabinoids.

• Epidiolex, which contains a purified form of CBD derived from cannabis, was approved for the treatment of seizures associated with Lennox-Gastaut syndrome or Dravet syndrome, two rare and severe forms of epilepsy.
• Marinol and Syndros, which contain dronabinol (synthetic THC), and Cesamet, which contains nabilone (a synthetic substance similar to THC), are approved by the FDA. Dronabinol and nabilone are used to treat nausea and vomiting caused by cancer chemotherapy. Dronabinol is also used to treat loss of appetite and weight loss in people with HIV/AIDS.

.header_greentext{color:green!important;font-size:24px!important;font-weight:500!important;}.header_bluetext{color:blue!important;font-size:18px!important;font-weight:500!important;}.header_redtext{color:red!important;font-size:28px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;font-size:28px!important;font-weight:500!important;}.header_purpletext{color:purple!important;font-size:31px!important;font-weight:500!important;}.header_yellowtext{color:yellow!important;font-size:20px!important;font-weight:500!important;}.header_blacktext{color:black!important;font-size:22px!important;font-weight:500!important;}.header_whitetext{color:white!important;font-size:22px!important;font-weight:500!important;}.header_darkred{color:#803d2f!important;}.Green_Header{color:green!important;font-size:24px!important;font-weight:500!important;}.Blue_Header{color:blue!important;font-size:18px!important;font-weight:500!important;}.Red_Header{color:red!important;font-size:28px!important;font-weight:500!important;}.Purple_Header{color:purple!important;font-size:31px!important;font-weight:500!important;}.Yellow_Header{color:yellow!important;font-size:20px!important;font-weight:500!important;}.Black_Header{color:black!important;font-size:22px!important;font-weight:500!important;}.White_Header{color:white!important;font-size:22px!important;font-weight:500!important;} Is it legal for dietary supplements or foods to contain THC or CBD?

The FDA has determined that products containing THC or CBD cannot be sold legally as dietary supplements . Foods to which THC or CBD has been added cannot be sold legally in interstate commerce. Whether they can be sold legally within a state depends on that state’s laws and regulations.

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Drugs containing cannabinoids may be helpful in treating certain rare forms of epilepsy, nausea and vomiting associated with cancer chemotherapy, and loss of appetite and weight loss associated with HIV/AIDS. In addition, some evidence suggests modest benefits of cannabis or cannabinoids for chronic pain and multiple sclerosis symptoms. Cannabis isn’t helpful for glaucoma . Research on cannabis or cannabinoids for other conditions is in its early stages.

The following sections summarize the research on cannabis or cannabinoids for specific health conditions.

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• Research has been done on the effects of cannabis or cannabinoids on chronic pain, particularly neuropathic pain (pain associated with nerve injury or damage).
• A 2018 review looked at 47 studies (4,743 participants) of cannabis or cannabinoids for various types of chronic pain other than cancer pain and found evidence of a small benefit. Twenty-nine percent of people taking cannabis/cannabinoids had a 30 percent reduction in their pain whereas 26 percent of those taking a placebo (an inactive substance) did. The difference may be too small to be meaningful to patients. Adverse events (side effects) were more common among people taking cannabis/cannabinoids than those taking placebos.
• A 2018 review of 16 studies of cannabis-based medicines for neuropathic pain, most of which tested a cannabinoid preparation called nabiximols (brand name Sativex; a mouth spray containing both THC and CBD that is approved in some countries but not in the United States), found low- to moderate-quality evidence that these medicines produced better pain relief than placebos did. However, the data could not be considered reliable because the studies included small numbers of people and may have been biased. People taking cannabis-based medicines were more likely than those taking placebos to drop out of studies because of side effects.
• A 2015 review of 28 studies (2,454 participants) of cannabinoids in which chronic pain was assessed found the studies generally showed improvements in pain measures in people taking cannabinoids, but these did not reach statistical significance in most of the studies. However, the average number of patients who reported at least a 30 percent reduction in pain was greater with cannabinoids than with placebo.

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• There’s evidence from studies in animals that administering THC along with opioids may make it possible to control pain with a smaller dose of opioids.
• A 2017 review looked at studies in people in which cannabinoids were administered along with opioids to treat pain. These studies were designed to determine whether cannabinoids could make it possible to control pain with smaller amounts of opioids. There were 9 studies (750 total participants), of which 3 (642 participants) used a high-quality study design in which participants were randomly assigned to receive cannabinoids or a placebo. The results were inconsistent, and none of the high-quality studies indicated that cannabinoids could lead to decreased opioid use.
• States with medical marijuana laws were found to have lower prescription rates both for opioids and for all drugs that cannabis could substitute for among people on Medicare. However, data from a national survey (not limited to people on Medicare) showed that users of medical marijuana were more likely than nonusers to report taking prescription drugs.
• An analysis of data from 1999 to 2010 indicated that states with medical marijuana laws had lower death rates from overdoses of opioid pain medicines, but when a similar analysis was extended through 2017, it showed higher death rates from this kind of overdose.
• An analysis of survey data from 2004 to 2014 found that passing of medical marijuana laws was not associated with less nonmedical prescription opioid use. Thus, people with access to medical marijuana did not appear to be substituting it for prescription opioids.

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• A small amount of evidence from studies in people suggests that cannabis or cannabinoids might help to reduce anxiety. One study of 24 people with social anxiety disorder found that they had less anxiety in a simulated public speaking test after taking CBD than after taking a placebo. Four studies have suggested that cannabinoids may be helpful for anxiety in people with chronic pain; the study participants did not necessarily have anxiety disorders.

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• Cannabinoids, primarily CBD, have been studied for the treatment of seizures associated with forms of epilepsy that are difficult to control with other medicines. Epidiolex (oral CBD) has been approved by the FDA for the treatment of seizures associated with two epileptic encephalopathies: Lennox-Gastaut syndrome and Dravet syndrome. (Epileptic encephalopathies are a group of seizure disorders that start in childhood and involve frequent seizures along with severe impairments in cognitive development.) Not enough research has been done on cannabinoids for other, more common forms of epilepsy to allow conclusions to be reached about whether they’re helpful for these conditions.

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• Glaucoma is a group of diseases that can damage the eye’s optic nerve, leading to vision loss and blindness. Early treatment can often prevent severe loss of vision. Lowering pressure in the eye can slow progression of the disease.
• Studies conducted in the 1970s and 1980s showed that cannabis or substances derived from it could lower pressure in the eye, but not as effectively as treatments already in use. One limitation of cannabis-based products is that they only affect pressure in the eye for a short period of time.
• A recent animal study showed that CBD, applied directly to the eye, may cause an undesirable increase in pressure in the eye.

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• Unintentional weight loss can be a problem for people with HIV/AIDS. In 1992, the FDA approved the cannabinoid dronabinol for the treatment of loss of appetite associated with weight loss in people with HIV/AIDS. This approval was based primarily on a study of 139 people that assessed effects of dronabinol on appetite and weight changes.
• There have been a few other studies of cannabis or cannabinoids for appetite and weight loss in people with HIV/AIDS, but they were short and only included small numbers of people, and their results may have been biased. Overall, the evidence that cannabis/cannabinoids are beneficial in people with HIV/AIDS is limited.

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• Inflammatory bowel disease is the name for a group of conditions in which the digestive tract becomes inflamed. Ulcerative colitis and Crohn’s disease are the most common types. Symptoms may include abdominal pain, diarrhea, loss of appetite, weight loss, and fever. The symptoms can range from mild to severe, and they can come and go, sometimes disappearing for months or years and then returning.
• A 2018 review looked at 3 studies (93 total participants) that compared smoked cannabis or cannabis oil with placebos in people with active Crohn’s disease. There was no difference between the cannabis/cannabis oil and placebo groups in clinical remission of the disease. Some people using cannabis or cannabis oil had improvements in symptoms, but some had undesirable side effects. It was uncertain whether the potential benefits of cannabis or cannabis oil were greater than the potential harms.
• A 2018 review examined 2 studies (92 participants) that compared smoked cannabis or CBD capsules with placebos in people with active ulcerative colitis. In the CBD study, there was no difference between the two groups in clinical remission, but the people taking CBD had more side effects. In the smoked cannabis study, a measure of disease activity was lower after 8 weeks in the cannabis group; no information on side effects was reported.

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• Irritable bowel syndrome (IBS) is defined as repeated abdominal pain with changes in bowel movements (diarrhea, constipation, or both). It’s one of a group of functional disorders of the gastrointestinal (GI) tract that relate to how the brain and gut work together.
• Although there’s interest in using cannabis/cannabinoids for symptoms of IBS, there’s been little research on their use for this condition in people. Therefore, it’s unknown whether cannabis or cannabinoids can be helpful.

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• A 2015 review of 2 small placebo-controlled studies with 36 participants suggested that synthetic THC capsules may be associated with a significant improvement in tic severity in patients with Tourette syndrome.

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• A review of 17 studies of a variety of cannabinoid preparations with 3,161 total participants indicated that cannabinoids caused a small improvement in spasticity (as assessed by the patient), pain, and bladder problems in people with multiple sclerosis, but cannabinoids didn’t significantly improve spasticity when measured by objective tests.
• A review of 6 placebo-controlled clinical trials with 1,134 total participants concluded that cannabinoids (nabiximols, dronabinol, and THC/CBD) were associated with a greater average improvement on the Ashworth scale for spasticity in multiple sclerosis patients compared with placebo, although this did not reach statistical significance.
• Evidence-based guidelines issued in 2014 by the American Academy of Neurology concluded that nabiximols is probably effective for improving subjective spasticity symptoms, probably ineffective for reducing objective spasticity measures or bladder incontinence, and possibly ineffective for reducing multiple sclerosis–related tremor. Based on two small studies, the guidelines concluded that the data are inadequate to evaluate the effects of smoked cannabis in people with multiple sclerosis.
• A 2010 analysis of 3 studies (666 participants) of nabiximols in people with multiple sclerosis and spasticity found that nabiximols reduced subjective spasticity, usually within 3 weeks, and that about one-third of people given nabiximols as an addition to other treatment would have at least a 30 percent improvement in spasticity. Nabiximols appeared to be reasonably safe.

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• A 2015 review of 23 studies (1,326 participants) on the cannabinoids dronabinol or nabilone for treating nausea and vomiting related to cancer chemotherapy found that they were more helpful than a placebo and similar in effectiveness to other medicines used for this purpose. More people had side effects such as dizziness or sleepiness, though, when taking the cannabinoid medicines.
• The research on dronabinol and nabilone for treating nausea and vomiting related to cancer chemotherapy was done primarily in the 1980s and 1990s and reflects the types of chemotherapy treatments and choices of antinausea medicines available at that time rather than current ones.

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• In one very small study (10 people), the cannabinoid nabilone was more effective than a placebo at relieving PTSD-related nightmares.
• Observational studies (studies that collected data on people with PTSD who made their own choices about whether to use cannabis) haven’t provided clear evidence on whether cannabis is helpful or harmful for PTSD symptoms.

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• Many studies of cannabis or cannabinoids in people with health problems (such as multiple sclerosis, PTSD, or chronic pain) have looked at effects on sleep. Often, there’s been evidence of better sleep quality, fewer sleep disturbances, or decreased time to fall asleep in people taking cannabis/cannabinoids. However, it’s uncertain whether the cannabis products affected sleep directly or whether people slept better because the symptoms of their illnesses had improved. The effects of cannabis/cannabinoids on sleep problems in people who don’t have other illnesses are uncertain.

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Several concerns have been raised about the safety of cannabis and cannabinoids:

• The use of cannabis has been linked to an increased risk of motor vehicle crashes.
• Smoking cannabis during pregnancy has been linked to lower birth weight.
• Some people who use cannabis develop cannabis use disorder, which has symptoms such as craving, withdrawal, lack of control, and negative effects on personal and professional responsibilities.
• Adolescents using cannabis are four to seven times more likely than adults to develop cannabis use disorder.
• Cannabis use is associated with an increased risk of injury among older adults.
• The use of cannabis, especially frequent use, has been linked to a higher risk of developing schizophrenia or other psychoses (severe mental illnesses) in people who are predisposed to these illnesses.
• Marijuana may cause orthostatic hypotension (head rush or dizziness on standing up), possibly raising danger from fainting and falls.
• The FDA has warned the public not to use vaping products that contain THC. Products of this type have been implicated in many of the reported cases of serious lung injuries linked to vaping.
• There have been many reports of unintentional consumption of cannabis or its products by children, leading to illnesses severe enough to require emergency room treatment or admission to a hospital. Among a group of people who became ill after accidental exposure to candies containing THC, the children generally had more severe symptoms than the adults and needed to stay in the hospital longer.
• Some long-term users of high doses of cannabis have developed a condition involving recurrent severe vomiting.
• There have been reports of contamination of cannabis/cannabinoid products with microorganisms, pesticides, or other substances.
• Some cannabis/cannabinoid products contain amounts of cannabinoids that differ substantially from what’s stated on their labels.

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Unlike Epidiolex (the purified CBD product sold as an FDA-approved prescription drug), over-the-counter CBD products may contain more or less CBD than stated on their labels, and because of less rigorous regulatory oversight than prescription drugs, they may also contain contaminants, such as THC.

CBD may have side effects, including decreases in alertness, changes in mood, decreased appetite, and gastrointestinal symptoms such as diarrhea. CBD may also produce psychotic effects or cognitive impairment in people who also regularly use THC. In addition, CBD use has been associated with liver injury, male reproductive harm, and interactions with other drugs. Some side effects, such as diarrhea, sleepiness, abnormalities on tests of liver function, and drug interactions, appear to be due to CBD itself rather than contaminants in CBD products; these effects were observed in some of the people who participated in studies of Epidiolex before its approval as a drug.

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Several NCCIH-funded studies are investigating the potential pain-relieving properties and mechanisms of action of substances in cannabis, including minor cannabinoids (those other than THC) and terpenes (substances in cannabis that give the plant its strain-specific properties such as aroma and taste). The goal of these studies is to strengthen the evidence regarding cannabis components and whether they have potential roles in pain management.

NCCIH is also supporting other studies on cannabis and cannabinoids, including:

• An observational study of the effects of edible cannabis and its constituents on pain, inflammation, and thinking in people with chronic low-back pain.
• Studies to develop techniques to synthesize cannabinoids in yeast (which would cost less than obtaining them from the cannabis plant).
• Research to evaluate the relationship between cannabis smoking and type 2 diabetes.

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• Don’t use cannabis or cannabinoids to postpone seeing a health care provider about a medical problem.
• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

For More Information

Nccih clearinghouse.

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

Toll-free in the U.S.: 1-888-644-6226

Telecommunications relay service (TRS): 7-1-1

Website: https://www.nccih.nih.gov

Email: [email protected] (link sends email)

Know the Science

NCCIH and the National Institutes of Health (NIH) provide tools to help you understand the basics and terminology of scientific research so you can make well-informed decisions about your health. Know the Science features a variety of materials, including interactive modules, quizzes, and videos, as well as links to informative content from Federal resources designed to help consumers make sense of health information.

Explaining How Research Works (NIH)

Know the Science: How To Make Sense of a Scientific Journal Article

Understanding Clinical Studies (NIH)

A service of the National Library of Medicine, PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. For guidance from NCCIH on using PubMed, see How To Find Information About Complementary Health Approaches on PubMed .

Website: https://pubmed.ncbi.nlm.nih.gov/

MedlinePlus

To provide resources that help answer health questions, MedlinePlus (a service of the National Library of Medicine) brings together authoritative information from the National Institutes of Health as well as other Government agencies and health-related organizations.

Website: https://www.medlineplus.gov

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• Kafil TS, Nguyen TM, MacDonald JK, et al. Cannabis for the treatment of Crohn’s disease . Cochrane Database of Systematic Reviews . 2018;(11):CD012853. Accessed at https://www.cochranelibrary.com/ on June 10, 2019.
• Kafil TS, Nguyen TM, MacDonald JK, et al. Cannabis for the treatment of ulcerative colitis . Cochrane Database of Systematic Reviews . 2018;(11):CD012954. Accessed at https://www.cochranelibrary.com/ on June 10, 2019.
• Lutge EE, Gray A, Siegfried N. The medical use of cannabis for reducing morbidity and mortality in patients with HIV/AIDS . Cochrane Database of Systematic Reviews . 2013;(4):CD005175. Accessed at https://www.cochranelibrary.com/ on June 10, 2019.
• Mücke M, Phillips T, Radbruch L, et al. Cannabis-based medicines for chronic neuropathic pain in adults . Cochrane Database of Systematic Reviews . 2018;(3):CD012182. Accessed at https://www.cochranelibrary.com/ on June 10, 2019.
• National Academies. The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research (link is external) . Washington, DC: The National Academies Press. 2017.
• Nielsen S, Sabioni P, Trigo JM, et al. Opioid-sparing effect of cannabinoids: a systematic review and meta-analysis . Neuropsychopharmacology . 2017;42(9):1752-1765.
• Richards JR, Smith NE, Moulin AK. Unintentional cannabis ingestion in children: a systematic review . Journal of Pediatrics . 2017;190:142-152.
• Segura LE, Mauro CM, Levy NS, et al. Association of US medical marijuana laws with nonmedical prescription opioid use and prescription opioid use disorder . JAMA Network Open . 2019;2(7):e197216.
• Shover CL, Davis CS, Gordon SC, et al. Association between medical cannabis laws and opioid overdose mortality has reversed over time . Proceedings of the National Academy of Sciences . 2019;116(26):12,624-12,626.
• Smith LA, Azariah F, Lavender VT, et al. Cannabinoids for nausea and vomiting in adults with cancer receiving chemotherapy . Cochrane Database of Systematic Reviews . 2015;(11):CD009464. Accessed at https://www.cochranelibrary.com on June 10, 2019.
• Stockings E, Campbell G, Hall WD, et al. Cannabis and cannabinoids for the treatment of people with chronic noncancer pain conditions: a systematic review and meta-analysis of controlled and observational studies . Pain . 2018;159(10):1932-1954.
• Torres-Moreno MC, Papaseit E, Torrens M, et al. Assessment of efficacy and tolerability of medicinal cannabinoids in patients with multiple sclerosis. A systematic review and meta-analysis . JAMA Network Open . 2018;1(6):e183485.
• U.S. Food and Drug Administration. Vaping illness update: FDA warns public to stop using tetrahydrocannabinol (THC)-containing vaping products and any vaping products obtained off the street. Accessed at https://www.fda.gov/safety/medical-product-safety-information/lung-injury-update-fda-warns-public-stop-using-tetrahydrocannabinol-thc-containing-vaping-products on October 9, 2019.
• Whiting PF, Wolff RF, Deshpande S, et al. Cannabinoids for medical use. A systematic review and meta-analysis . JAMA . 2015;313(24):2456-2463.
• Yadav V, Bever C Jr, Bowen J, et al. Summary of evidence-based guideline: complementary and alternative medicine in multiple sclerosis: report of the Guideline Development Subcommittee of the American Academy of Neurology . Neurology . 2014;82(12):1083-1092.

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• Amin MR, Ali DW. Pharmacology of medical cannabis. Advances in Experimental Medicine and Biology . 2019;1162:151-165.
• Bachhuber MA, Saloner B, Cunningham CO, et al. Medical cannabis laws and opioid analgesic overdose mortality in the United States, 1999-2010. JAMA Internal Medicine . 2014;174(10):1668-1673.
• Beal JE, Olson R, Laubenstein L, et al. Dronabinol as a treatment for anorexia associated with weight loss in patients with AIDS. Journal of Pain and Symptom Management . 1995;10(2):89-97.
• Bergamaschi MM, Queiroz RH, Chagas MH, et al. Cannabidiol reduces the anxiety induced by simulated public speaking in treatment-naïve social phobia patients. Neuropsychopharmacology . 2011;36(6):1219-1226.
• Bonn-Miller MO, Loflin MJE, Thomas BF, et al. Labeling accuracy of cannabidiol extracts sold online. JAMA . 2017;318(17):1708-1709.
• Bradford AC, Bradford WD, Abraham A, et al. Association between US state medical cannabis laws and opioid prescribing in the Medicare Part D population. JAMA Internal Medicine . 2018;178(5):667-672.
• Bradford AC, Bradford WD. Medical marijuana laws reduce prescription medication use in Medicare Part D. Health Affairs . 2016;35(7):1230-1236.
• Brodie MJ, Ben-Menachem E. Cannabinoids for epilepsy: what do we know and where do we go? Epilepsia . 2018;59(2):291-296.
• Caputi TL, Humphreys K. Medical marijuana users are more likely to use prescription drugs medically and nonmedically. Journal of Addiction Medicine . 2018;12(4):295-299.
• Choi NG, DiNitto DM, Marti CN, et al. Association between nonmedical marijuana and pain reliever uses among individuals aged 50+. Journal of Psychoactive Drugs . 2017;49(4):267-278.
• Gaston TE, Szaflarski JP. Cannabis for the treatment of epilepsy: an update. Current Neurology and Neuroscience Reports . 2018;18(11):73.
• Goyal H, Awad HH, Ghali JK. Role of cannabis in cardiovascular disorders. Journal of Thoracic Disease . 2017;9(7):2079-2092.
• Hasin DS, Saha TD, Kerridge BT, et al. Prevalence of marijuana use disorders in the United States between 2001-2002 and 2012-2013. JAMA Psychiatry . 2015;72(12):1235-1242.
• Jetly R, Heber A, Fraser G, et al. The efficacy of nabilone, a synthetic cannabinoid, in the treatment of PTSD-associated nightmares: a preliminary randomized, double-blind, placebo-controlled cross-over design study. Psychoneuroendocrinology . 2015;51:585-588.
• Khattar N, Routsoloias JC. Emergency department treatment of cannabinoid hyperemesis syndrome: a review. American Journal of Therapeutics . 2018;25(3):e357-e361.
• Kuhathasan N, Dufort A, MacKillop J, et al. The use of cannabinoids for sleep: a critical review on clinical trials. Experimental and Clinical Psychopharmacology . 2019;27(4):383-401.
• Lafaye G, Karila L, Blecha L, et al. Cannabis, cannabinoids, and health. Dialogues in Clinical Neuroscience . 2017;19(3):309-316.
• Miller S, Daily L, Leishman E, et al. Δ9-Tetrahydrocannabinol and cannabidiol differentially regulate intraocular pressure. Investigative Ophthalmology & Visual Science . 2018;59(15):5904-5911.
• National Cancer Institute. Cannabis and cannabinoids (PDQ®)—health professional version. Accessed at https://www.cancer.gov/about-cancer/treatment/cam/hp/cannabis-pdq#section/_1 on June 12, 2019.
• National Institute on Drug Abuse. NIH research on marijuana and cannabinoids. Downloaded from https://www.drugabuse.gov/drugs-abuse/marijuana/nih-research-marijuana-cannabinoids on June 12, 2019.
• Novack GD. Cannabinoids for treatment of glaucoma. Current Opinion in Ophthalmology . 2016;27(2):146-150.
• O’Connell BK, Gloss D, Devinsky O. Cannabinoids in treatment-resistant epilepsy: a review. Epilepsy & Behavior . 2017;70(Pt B):341-348.
• O’Neil ME, Nugent SM, Morasco BJ, et al. Benefits and harms of plant-based cannabis for posttraumatic stress disorder. A systematic review. Annals of Internal Medicine . 2017;167(5):332-340.
• Substance Abuse and Mental Health Services Administration. Cannabidiol (CBD): Potential Harms, Side Effects, and Unknowns . Accessed at  https://store.samhsa.gov/sites/default/files/pep22-06-04-003.pdf on February 24, 2023.
• U.S. Food and Drug Administration. FDA regulation of cannabis and cannabis-derived products: questions and answers. Accessed at https://www.fda.gov/news-events/public-health-focus/fda-regulation-cannabis-and-cannabis-derived-products-questions-and-answers on June 12, 2019.
• Vandrey R, Raber JC, Raber ME, et al. Cannabinoid dose and label accuracy in edible medical cannabis products. JAMA . 2015;313(24):2491-2493.
• Vo KT, Horng H, Li K, et al. Cannabis intoxication case series: the dangers of edibles containing tetrahydrocannabinol. Annals of Emergency Medicine . 2018;71(3):306-313.
• Volkow ND, Baler RD, Compton WM, et al. Adverse health effects of marijuana use. New England Journal of Medicine . 2014;370(23):2219-2227.
• Wade DT, Collin C, Stott C, et al. Meta-analysis of the efficacy and safety of Sativex (nabiximols), on spasticity in people with multiple sclerosis. Multiple Sclerosis . 2010;16(6):707-714.
• Winters KC, Lee C-Y. Likelihood of developing an alcohol and cannabis use disorder during youth: association with recent use and age. Drug and Alcohol Dependence . 2008;92(1-3):239-247.

Acknowledgments

NCCIH thanks D. Craig Hopp, Ph.D., Inna Belfer, M.D., Ph.D., and David Shurtleff, Ph.D., NCCIH, for their review of the 2019 edition of this publication.

This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your health care provider(s). We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.

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Researchers find antipsychotics help ease episodes of marijuana-induced psychosis

by Ernie Mundell

Overuse of marijuana is increasingly being linked to dangerous bouts of psychosis, and a new study finds that antipsychotics may be needed to keep such patients out of the hospital.

Psychotic episodes involve a dangerous psychiatric state in which people lose their connection with reality. These episodes can get so out of control that people may need hospitalization.

However, new research finds that people who overuse marijuana and then experience their first psychotic episode may be helped by the quick use of injected antipsychotics.

"These findings encourage the early use of second-generation, long-acting injectables as an important secondary prevention strategy to reduce rates of hospitalization" in such patients, reports a team led by Dr. Alexander Denissoff, of the University of Turku in Finland.

His team tracked outcomes for 1,820 people who had a first psychotic episode and also had cannabis use disorder between 2006 and 2021.

Just over 1,100 of these patients ended up being hospitalized due to "psychotic relapse," according to the American Psychiatric Association news release. However, folks who had received any antipsychotic med were a third less likely to require hospitalization due to relapse, compared to those who hadn't gotten these drugs.

Comparing the effectiveness of various antipsychotics , risperidone came out on top, cutting the odds for relapse-linked hospitalization by 60%, the researchers found, followed by aripiprazole (58% reduction), oral clozapine (57%), and paliperidone (54%).

Denissoff's team stressed the odds that a person with cannabis use disorder experiences multiple psychotic episodes rises if they use marijuana after experiencing a first episode and/or do not take antipsychotic medicines as prescribed.

For those who were hospitalized due to any substance use disorder , clozapine seemed to work best, with an 86% lower risk of re-hospitalization due to any substance use, followed by risperidone (67%) and paliperidone (63%), the researchers said.

The findings were published recently in the journal Schizophrenia Bulletin .

© 2024 HealthDay . All rights reserved.

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Read our research on: Gun Policy | International Conflict | Election 2024

Regions & Countries

Most americans favor legalizing marijuana for medical, recreational use, legalizing recreational marijuana viewed as good for local economies; mixed views of impact on drug use, community safety.

Pew Research Center conducted this study to understand the public’s views about the legalization of marijuana in the United States. For this analysis, we surveyed 5,140 adults from Jan. 16 to Jan. 21, 2024. Everyone who took part in this survey is a member of the Center’s American Trends Panel (ATP), an online survey panel that is recruited through national, random sampling of residential addresses. This way nearly all U.S. adults have a chance of selection. The survey is weighted to be representative of the U.S. adult population by gender, race, ethnicity, partisan affiliation, education and other categories. Read more about the ATP’s methodology .

Here are the questions used for the report and its methodology .

As more states pass laws legalizing marijuana for recreational use , Americans continue to favor legalization of both medical and recreational use of the drug.

An overwhelming share of U.S. adults (88%) say marijuana should be legal for medical or recreational use.

Nearly six-in-ten Americans (57%) say that marijuana should be legal for medical and recreational purposes, while roughly a third (32%) say that marijuana should be legal for medical use only.

Just 11% of Americans say that the drug should not be legal at all.

Opinions about marijuana legalization have changed little over the past five years, according to the Pew Research Center survey, conducted Jan. 16-21, 2024, among 5,14o adults.

The impact of legalizing marijuana for recreational use

While a majority of Americans continue to say marijuana should be legal , there are varying views about the impacts of recreational legalization.

About half of Americans (52%) say that legalizing the recreational use of marijuana is good for local economies; just 17% think it is bad and 29% say it has no impact.

More adults also say legalizing marijuana for recreational use makes the criminal justice system more fair (42%) than less fair (18%); 38% say it has no impact.

However, Americans have mixed views on the impact of legalizing marijuana for recreational use on:

• Use of other drugs: About as many say it increases (29%) as say it decreases (27%) the use of other drugs, like heroin, fentanyl and cocaine (42% say it has no impact).
• Community safety: More Americans say legalizing recreational marijuana makes communities less safe (34%) than say it makes them safer (21%); 44% say it has no impact.

Partisan differences on impact of recreational use of marijuana

There are deep partisan divisions regarding the impact of marijuana legalization for recreational use.

Majorities of Democrats and Democratic-leaning independents say legalizing recreational marijuana is good for local economies (64% say this) and makes the criminal justice system fairer (58%).

Fewer Republicans and Republican leaners say legalization for recreational use has a positive effect on local economies (41%) and the criminal justice system (27%).

Republicans are more likely than Democrats to cite downsides from legalizing recreational marijuana:

• 42% of Republicans say it increases the use of other drugs, like heroin, fentanyl and cocaine, compared with just 17% of Democrats.
• 48% of Republicans say it makes communities less safe, more than double the share of Democrats (21%) who say this.

Demographic, partisan differences in views of marijuana legalization

Sizable age and partisan differences persist on the issue of marijuana legalization though small shares of adults across demographic groups are completely opposed to it.

Older adults are far less likely than younger adults to favor marijuana legalization.

This is particularly the case among adults ages 75 and older: 31% say marijuana should be legal for both medical and recreational use.

By comparison, half of adults between the ages of 65 and 74 say marijuana should be legal for medical and recreational use, and larger shares in younger age groups say the same.

Republicans continue to be less supportive than Democrats of legalizing marijuana for both legal and recreational use: 42% of Republicans favor legalizing marijuana for both purposes, compared with 72% of Democrats.

There continue to be ideological differences within each party:

• 34% of conservative Republicans say marijuana should be legal for medical and recreational use, compared with a 57% majority of moderate and liberal Republicans.
• 62% of conservative and moderate Democrats say marijuana should be legal for medical and recreational use, while an overwhelming majority of liberal Democrats (84%) say this.

Views of marijuana legalization vary by age within both parties

Along with differences by party and age, there are also age differences within each party on the issue.

A 57% majority of Republicans ages 18 to 29 favor making marijuana legal for medical and recreational use, compared with 52% among those ages 30 to 49 and much smaller shares of older Republicans.

Still, wide majorities of Republicans in all age groups favor legalizing marijuana at least for medical use. Among those ages 65 and older, just 20% say marijuana should not be legal even for medical purposes.

While majorities of Democrats across all age groups support legalizing marijuana for medical and recreational use, older Democrats are less likely to say this.

About half of Democrats ages 75 and older (53%) say marijuana should be legal for both purposes, but much larger shares of younger Democrats say the same (including 81% of Democrats ages 18 to 29). Still, only 7% of Democrats ages 65 and older think marijuana should not be legalized even for medical use, similar to the share of all other Democrats who say this.

Views of the effects of legalizing recreational marijuana among racial and ethnic groups

Substantial shares of Americans across racial and ethnic groups say when marijuana is legal for recreational use, it has a more positive than negative impact on the economy and criminal justice system.

About half of White (52%), Black (53%) and Hispanic (51%) adults say legalizing recreational marijuana is good for local economies. A slightly smaller share of Asian adults (46%) say the same.

Criminal justice

Across racial and ethnic groups, about four-in-ten say that recreational marijuana being legal makes the criminal justice system fairer, with smaller shares saying it would make it less fair.

However, there are wider racial differences on questions regarding the impact of recreational marijuana on the use of other drugs and the safety of communities.

Use of other drugs

Nearly half of Black adults (48%) say recreational marijuana legalization doesn’t have an effect on the use of drugs like heroin, fentanyl and cocaine. Another 32% in this group say it decreases the use of these drugs and 18% say it increases their use.

In contrast, Hispanic adults are slightly more likely to say legal marijuana increases the use of these other drugs (39%) than to say it decreases this use (30%); 29% say it has no impact.

Among White adults, the balance of opinion is mixed: 28% say marijuana legalization increases the use of other drugs and 25% say it decreases their use (45% say it has no impact). Views among Asian adults are also mixed, though a smaller share (31%) say legalization has no impact on the use of other drugs.

Community safety

Hispanic and Asian adults also are more likely to say marijuana’s legalization makes communities less safe: 41% of Hispanic adults and 46% of Asian adults say this, compared with 34% of White adults and 24% of Black adults.

Wide age gap on views of impact of legalizing recreational marijuana

Young Americans view the legalization of marijuana for recreational use in more positive terms compared with their older counterparts.

Clear majorities of adults under 30 say it is good for local economies (71%) and that it makes the criminal justice system fairer (59%).

By comparison, a third of Americans ages 65 and older say legalizing the recreational use of marijuana is good for local economies; about as many (32%) say it makes the criminal justice system more fair.

There also are sizable differences in opinion by age about how legalizing recreational marijuana affects the use of other drugs and the safety of communities.

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Table of contents, most americans now live in a legal marijuana state – and most have at least one dispensary in their county, 7 facts about americans and marijuana, americans overwhelmingly say marijuana should be legal for medical or recreational use, clear majorities of black americans favor marijuana legalization, easing of criminal penalties, religious americans are less likely to endorse legal marijuana for recreational use, most popular.

About Pew Research Center Pew Research Center is a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping the world. It conducts public opinion polling, demographic research, media content analysis and other empirical social science research. Pew Research Center does not take policy positions. It is a subsidiary of The Pew Charitable Trusts .

Cannabis (Marijuana) Research Report Is marijuana safe and effective as medicine?

The potential medicinal properties of marijuana and its components have been the subject of research and heated debate for decades. THC itself has proven medical benefits in particular formulations. The U.S. Food and Drug Administration (FDA) has approved THC-based medications, dronabinol (Marinol ® ) and nabilone (Cesamet ® ), prescribed in pill form for the treatment of nausea in patients undergoing cancer chemotherapy and to stimulate appetite in patients with wasting syndrome due to AIDS.

In addition, several other marijuana-based medications have been approved or are undergoing clinical trials. Nabiximols (Sativex ® ), a mouth spray that is currently available in the United Kingdom, Canada, and several European countries for treating the spasticity and neuropathic pain that may accompany multiple sclerosis, combines THC with another chemical found in marijuana called cannabidiol (CBD).

The FDA also approved a CBD-based liquid medication called Epidiolex ®  for the treatment of two forms of severe childhood epilepsy, Dravet syndrome and Lennox-Gastaut syndrome. It’s being delivered to patients in a reliable dosage form and through a reproducible route of delivery to ensure that patients derive the anticipated benefits. CBD does not have the rewarding properties of THC.

Researchers generally consider medications like these, which use purified chemicals derived from or based on those in the marijuana plant, to be more promising therapeutically than use of the whole marijuana plant or its crude extracts. Development of drugs from botanicals such as the marijuana plant poses numerous challenges. Botanicals may contain hundreds of unknown, active chemicals, and it can be difficult to develop a product with accurate and consistent doses of these chemicals. Use of marijuana as medicine also poses other problems such as the adverse health effects of smoking and THC-induced cognitive impairment. Nevertheless, a growing number of states have legalized dispensing of marijuana or its extracts to people with a range of medical conditions.

An additional concern with "medical marijuana" is that little is known about the long-term impact of its use by people with health- and/or age-related vulnerabilities—such as older adults or people with cancer, AIDS, cardiovascular disease, multiple sclerosis, or other neurodegenerative diseases. Further research will be needed to determine whether people whose health has been compromised by disease or its treatment (e.g., chemotherapy) are at greater risk for adverse health outcomes from marijuana use.

Medical Marijuana Laws and Prescription Opioid Use Outcomes

A 2019 analysis, also funded by NIDA, re-examined this relationship using data through 2017. Similar to the findings reported previously, this research team found that opioid overdose mortality rates between 1999-2010 in states allowing medical marijuana use were 21% lower than expected. When the analysis was extended through 2017, however, they found that the trend reversed, such that states with medical cannabis laws experienced an overdose death rate 22.7% higher than expected. 79 The investigators uncovered no evidence that either broader cannabis laws (those allowing recreational use) or more restrictive laws (those only permitting the use of marijuana with low tetrahydrocannabinol concentrations) were associated with changes in opioid overdose mortality rates.

These data, therefore, do not support the interpretation that access to cannabis reduces opioid overdose. Indeed, the authors note that neither study provides evidence of a causal relationship between marijuana access and opioid overdose deaths. Rather, they suggest that the associations are likely due to factors the researchers did not measure, and they caution against drawing conclusions on an individual level from ecological (population-level) data. Research is still needed on the potential medical benefits of cannabis or cannabinoids.

New Growing Method Skips Weed Vegetative Stage, Slashing Electricity And HVAC Costs, Preserving Yield And Quality

Fluence and Innexo BV have announced research that could revolutionize cannabis cultivation, proposing to eliminate the vegetative phase and potentially cut electricity costs by up to 55%. This approach promises significant energy savings and aims to improve quality and consistency for growers worldwide.

A Shift Towards Efficiency

The partnership between Fluence , a leader in energy-efficient LED lighting solutions, and Innexo, a Dutch research organization specializing in agricultural innovations, has focused on the feasibility of cultivating cannabis directly in its flowering stage.

This method, bypassing the vegetative phase typically required for plant development, could redefine cultivation strategies, offering a more sustainable and cost-effective model.

In a press release procured by Benzinga Cannabis, Dominique van Gruisen , Innexo’s managing director, stressed the alignment of both organizations in their commitment to groundbreaking cannabis research.

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“At Innexo, we use our deep knowledge of cannabis cultivars and best propagation practices to help growers create the most efficient cultivation strategies possible,” van Gruisen said. “We naturally gravitate toward partners like Fluence who can match our expertise and commitment to investing in innovative and impactful cannabis research.”

The initial phase of their research has already shown promising results, with potential reductions in electrical and labor costs by 40% and a decrease in pest and disease development due to the shortened growth cycle.

Transforming Cultivation Practices

Traditionally, cannabis plants undergo a vegetative stage lasting up to four weeks, consuming significant resources. However, Fluence and Innexo’s approach accelerates the process by transitioning plants directly to the flowering stage, significantly cutting down on electricity and HVAC costs.

This method not only achieves energy efficiency but also maintains crop yield and quality.

Dr. David Hawley , principal scientist at Fluence emphasized the importance of advanced lighting fixtures and strategies in this innovative cultivation method.

“Proper lighting—which must include a strong combination of advanced fixtures and lighting strategy—plays a critical role in creating a more efficient and profitable methodology for cannabis cultivation,” Dr. Hawley said.

“At Fluence, we create value for growers throughout the world by investing in research that will expand the horizons of traditional cultivation ,” added Sebastian Olschowski , research project manager for EMEA at Fluence. "As plant lighting specialists, we are proud to be part of this project to shape the future of cannabis research and transfer valuable knowledge to our customers and partners.”

Future Horizons

The collaboration has already expanded to include three of Innexo’s Acceleration Platform for Innovation programs, underscoring the potential for this research to benefit small-scale companies and the broader cannabis industry.

Benzinga Cannabis Conferences  are coming to Los Angeles. Join the  Benzinga Cannabis Market Spotlight: California , and unlock the future of cannabis at the premier networking event in Culver City on February 22. Connect with top industry leaders, gain insider insights into the investment landscape, and shape the evolving markets in California and beyond. Don’t miss this chance to be at the forefront of the cannabis industry’s growth and innovation!  Join now . 

Photo: AI-Generated Image. 

© 2024 Benzinga.com. Benzinga does not provide investment advice. All rights reserved.

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This article New Growing Method Skips Weed Vegetative Stage, Slashing Electricity And HVAC Costs, Preserving Yield And Quality originally appeared on Benzinga.com .