Black N, Stockings E, Campbell G, et al. - Analysing the available evidence, researchers sought to determine the efficacy and safety of all types of medicinal cannabinoids in treating symptoms of various mental disorders. They assessed 83 eligible studies (40 randomised controlled trials, n = 3,067): 42 for depression (23 randomised controlled trials; n = 2,551), 31 for anxiety (17 randomised controlled trials; n = 605), eight for Tourette syndrome (two randomised controlled trials; n = 36), three for attention-deficit hyperactivity disorder (one randomised controlled trial; n = 30), 12 for posttraumatic stress disorder (one randomised controlled trial; n = 10), and 11 for psychosis (six randomised controlled trials; n = 281). This study yielded scarce evidence suggesting the utility of cannabinoids for improving depressive disorders and symptoms, anxiety disorders, attention-deficit hyperactivity disorder, Tourette syndrome, posttraumatic stress disorder, or psychosis. Very low-quality evidence suggested the efficacy of pharmaceutical tetrahydrocannabinol (with or without cannabidiol) in providing a small improvement in symptoms of anxiety among individuals with other medical conditions. Insufficient evidence was gained to afford guidance on the application of cannabinoids for treating mental disorders within a regulatory framework.