A systematic review and meta-analysis published in the Lancet Psychiatry has delivered the most comprehensive verdict yet on medicinal cannabis for mental health conditions. Analysing 54 randomised controlled trials from around the world over 45-year span (1980-2025) researchers from the University of Sydney’s Matilda Centre found that there is no significant benefit of cannabinoids for treating:
- Anxiety
- Post-Traumatic Stress Disorder (PTSD)
- Anorexia Nervosa
- Psychotic Disorders
- Opioid Use Disorder
There was also insufficient evidence to draw firm conclusions on the effects of medicinal cannabis on attention deficit hyperactivity disorder (ADHD), bipolar disorder, obsessive-compulsive disorder (OCD) and tobacco use disorder. The results also suggested that there were no significant benefit for depression.
This is the largest review to date to examine both the efficacy and safety of cannabinoids across a wide range of mental health and substance disorders.
Why Medical Cannabis for Mental Health Matters Now?
Medicinal cannabis use is widespread in the United States and Canada with approximately 27% of people aged between 16 and 65 reporting they use it for medical purposes.
With medicinal cannabis use widespread, Dr Wilson, lead researcher at The Matilda Centre warned that “the routine use of medicinal cannabis could be doing more harm than good by worsening mental health outcomes, for example a greater risk of psychotic symptoms and developing cannabis use disorders and delaying the use of more effective treatments.”
Where Medical Cannabis May Have Limited Benefits?
The Matilda Centre’s review identified low-quality evidence suggesting medicinal cannabis benefits for:
- Longer sleep time in people with insomnia.
- Reduced severity of tics in Tourette’s Syndrome.
- Lower cannabis uses for those with cannabis use disorders (CUD).
- Reduce autistic traits in individuals with Autism Spectrum Disorder (ASD).
The analysis also confirmed established benefits outside of mental health such as reducing seizures associated with some forms of epilepsy, spasticity in individuals with multiple sclerosis and certain forms of pain managements.
Notably, the study found a negative effect with medicinal cannabis increasing cocaine craving in people with cocaine use disorders.
Safety Concerns of Medical Cannabis for Mental Health
Participants receiving medicinal cannabis experience significantly more adverse events compared to those who were given the placebo, with roughly 1 in 7 participants experiencing an adverse event. Supporting research from Johns Hopkins University adds further context on use with teenagers. Teenagers with cannabis use disorder (CUD) have a significantly higher risk of developing psychiatric disorders with schizophrenia being the highest possibility at 52%, followed by recurrent major depression (30%) and anxiety (21%).These risks appear unique to teenagers who use cannabis compared to other substances used by their peers, in the development of adolescent brains and do not show the same pattern in adults.
This was further supported with the 1987 study conducted with over 45,000 male Swedish army recruits, aged between 18-20, that found that the use of heavy cannabis use increased the risk of schizophrenia.
Expert Concerns About Medical Cannabis Regulation
The rapid rise in medicinal cannabis prescribing has raised serious concerns among major medical organisations, including the American Medical Association. Experts highlight the limited regulation and ongoing uncertainty about the real-world safety and effectiveness of these products.
Professor Owen, Bowden-Jones, Registrar of the Royal College of Psychiatrists, said this on the Lancet 2026 Review:
“This rigorously conducted study gives us the clearest indication yet that the benefits of cannabis as a medicine may have been overstated for many conditions.”
Further Dr Wilson and the University of Sydney research team emphasised that the study offer clinicians a complete assessment of both benefits and risks.
“Our study provides a comprehensive and independent assessment of the benefits and risks of cannabis medicines, which may support clinicians to make evidence-based decisions, helping to ensure patients receive effective treatments while minimising harm from ineffective or unsafe cannabis products”.
What this means for patients and clinicians?
This Lancet review makes one thing clear; medicinal cannabis is not a first line or proven evidence-based solution for anxiety, depression or PTSD. While it may have limited roles in specific conditions such as insomnia, Tourette’s syndrome or for certain pain-based conditions, the data does not support the widespread use for common mental health disorders.
The findings reinforce the importance of prioritising proven therapies and treating medicinal cannabis with the same scrutiny applied to any other treatments. For anyone considering medical cannabis for mental health, the message from this 45-year global analysis is straightforward: talk to your doctor about proven options first.
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