A major review has found that medicinal cannabis is not an effective treatment for common mental health conditions, despite a global increase in patients using it for this purpose. Researchers from universities in Australia and the UK concluded there was 'very little evidence for its efficacy' in treating anxiety, anorexia nervosa, psychotic disorders, post-traumatic stress disorder, or opioid use disorder.
The analysis, published in The Lancet Psychiatry, examined 54 randomised controlled trials involving 2,477 participants. It found no significant effects on outcomes for these conditions. The review was prompted by the legalisation of cannabis-based treatments in countries including the UK, US, Australia, and Canada.
Evidence from clinics shows that mental illnesses such as anxiety and depression are the main reasons patients cite for using medical cannabis, followed by chronic pain. However, the researchers said there was too little evidence for conditions like ADHD, bipolar disorder, and OCD, and none at all for depression.
Professor Sir Robin Murray of King's College London said many people are 'misled into using cannabis to treat their problems' and described UK cannabis clinics as 'drug dealers for the middle class'. However, Mike Morgan-Giles of the Cannabis Industry Council argued that real-world evidence shows medical cannabis reduces symptoms for anxiety and PTSD.
The Advisory Council on the Misuse of Drugs is currently reviewing the impact of the 2018 legalisation of cannabis-based products in the UK. Professor Owen Bowden-Jones of the Royal College of Psychiatrists said the study gives 'the clearest indication yet that the benefits of cannabis as a medicine may have been overstated'.
