The most comprehensive analysis of medicinal cannabinoids and their impact on six mental health disorders suggests the use of these therapies cannot be justified, based on the current evidence.
The study, published in the Lancet Psychiatry, combined 83 studies including 3,000 people to examine the safety and efficacy of medicinal cannabinoids to relieve depression, anxiety disorders, attention-deficit hyperactivity disorder (ADHD), Tourette’s syndrome, post-traumatic stress disorder (PTSD) or psychosis.
The authors found that pharmaceutical tetrahydrocannabinol (THC), with or without cannabidiol (CBD), improved anxiety symptoms among individuals with other medical conditions, primarily chronic non-cancer pain and multiple sclerosis (standardised mean differences [SMD] −0.25; 95% CI −0.49 to −0.01), although the quality of the evidence was very low.
Pharmaceutical THC, with or without CBD, worsened negative symptoms of psychosis in a single study (SMD 0.36; 95% CI 0.10-0.62; n=24).
Pharmaceutical THC, with or without CBD, did not significantly affect any other primary outcomes for the mental disorders examined but did increase the number of people who had adverse events (OR 1.99; 95% CI 1.20-3.29) compared with placebo.
The authors say the study highlights the need for investment in high-quality research into the effects of different cannabinoids on a range of outcomes for people with mental health disorders.