Systematic review finds limited evidence for medicinal cannabis treating mental health conditions
Consensus Summary
A large-scale systematic review published in The Lancet Psychiatry found no evidence that medicinal cannabis effectively treats common mental health conditions like anxiety, depression, or PTSD, despite its widespread prescription in Australia and other countries. The study, involving 54 randomized controlled trials with 2,477 participants, concluded that routine use of cannabinoids for these disorders is not justified due to insufficient high-quality research. While some low-quality evidence suggested potential benefits for Tourette’s syndrome, insomnia, and autism traits, experts emphasized the need for more rigorous trials. Prescriptions in Australia surged from fewer than 20,000 in 2020 to nearly a million in the last financial year, with mental health conditions among the top reasons for use. Critics, including researchers and industry representatives, debated the review’s findings, with some arguing it overlooked real-world patient benefits and others highlighting gaps in research funding and clinical trial quality. A personal case in the SMH illustrated how one individual’s reliance on medicinal cannabis worsened his mental health before quitting, while industry groups and clinicians defended its use for specific conditions.
✓ Verified by 2+ sources
Key details reported by multiple sources:
- Medicinal cannabis prescriptions in Australia increased from fewer than 20,000 in 2020 to nearly 1 million in the last financial year (SMH, Guardian).
- The University of Sydney-led review analyzed 54 randomized controlled trials involving 2,477 participants (Guardian) and found no evidence medicinal cannabis effectively treats anxiety, depression, or PTSD (SMH, Guardian).
- Researchers found some low-quality evidence that medicinal cannabis may reduce tic severity in Tourette’s syndrome, increase sleep time for insomniacs, and help manage autism traits (SMH, Guardian).
- The review was published in *The Lancet Psychiatry* (Guardian) and involved researchers from the University of Sydney, Brisbane, Melbourne, and Bath (Guardian).
- Daniel Yacoel, 33, from Darwin, reported improved mental health and sleep after quitting medicinal cannabis after two years of use (SMH).
- Legal cannabis sales in Australia have tripled in four years, but research has not kept pace with prescribing rates (SMH).
- The review concluded routine use of cannabinoids for mental health disorders is rarely justified due to scarcity of evidence (Guardian).
Points of Difference
Details reported by only one source:
- The review was published on Tuesday (exact date not specified) and included psychiatric and mental health conditions as the most common reasons for medicinal cannabis prescriptions in Australia (250,000+ for anxiety, 19,000 for PTSD, 17,641 for depression) (federal government data).
- Dr Jack Wilson (University of Sydney’s Matilda Centre) noted very few randomized control trials had assessed safety and effectiveness of medicinal cannabis, despite its legalization in Australia in 2016.
- Iain McGregor (University of Sydney) highlighted that the review did not distinguish between THC-dominant and CBD-dominant cannabis products, and criticized the industry’s lack of investment in randomized clinical trials (costing $3M–$10M each).
- The Cannabis Council spokesperson referenced TGA regulatory review submissions from patients describing benefits but did not directly address industry funding of clinical trials.
- Daniel Yacoel’s case included specific details: consuming 60 grams of cannabis monthly, spending more on scripts than his $300 weekly rent, and noting addiction awareness after quitting.
- The review included universities in Brisbane and Melbourne alongside Sydney and Bath (England), and was prompted by global legalization trends in the US, UK, Australia, and Canada.
- Sir Robin Murray (King’s College London) called cannabis clinics in the UK ‘drug dealers for the middle class’ and criticized the cannabis industry’s influence on patient claims.
- Mike Morgan-Giles (Cannabis Industry Council) disputed the review’s findings, citing ‘real-world evidence’ from T21 clinics showing cannabis reduces anxiety and PTSD symptoms.
- The Advisory Council on the Misuse of Drugs in the UK is reviewing the 2018 legalization of cannabis-based products, including unintended consequences.
- Prof Owen Bowden-Jones (Royal College of Psychiatrists) stated the review ‘gives the clearest indication yet that the benefits of cannabis as a medicine may have been overstated for many conditions’.
Contradictions
Conflicting information between sources:
- The Guardian reports the review found ‘very little evidence’ for cannabis efficacy in mental health conditions, while the Cannabis Industry Council (quoted in the Guardian) claims ‘real-world evidence’ shows it reduces anxiety and PTSD symptoms.
- The SMH states the review found ‘no evidence’ medicinal cannabis treats anxiety, depression, or PTSD, but the Guardian’s Mike Morgan-Giles argues the review ‘does not adequately reflect how clinical prescribing is undertaken in the UK’ for these conditions.
- The Guardian’s Sir Robin Murray calls cannabis clinics ‘drug dealers for the middle class,’ while the Cannabis Council (SMH) supports high-quality research without directly addressing industry funding gaps or patient misinformation risks.
- The SMH reports the review did not distinguish between THC and CBD products, which Iain McGregor (SMH) calls a weakness, but the Guardian does not mention this distinction as a specific criticism.
- The Guardian’s review found ‘no reason to believe’ cannabis helps depression, while the SMH notes the review lacked evidence for depression but did not explicitly state a negative conclusion for it.
Source Articles
The $300 a week medicine Daniel feels better without
Daniel Yacoel is one of hundreds of thousands of Australians prescribed medicinal cannabis for a mental health condition but there is little evidence it works....
Cannabis is not an effective treatment for common mental health conditions, says review
International researchers find ‘very little evidence’ medical form of the drug can treat anxiety, anorexia and other disorders Cannabis is not an effective treatment for common mental health condition...