Cannabinoids for Psychiatric Disorders? Evidence of Effectiveness is Lacking, Report Concludes

There is little evidence that the use of cannabinoids can improve symptoms of anxiety, attention-deficit/hyperactivity disorder (ADHD), depression, posttraumatic stress disorder (PTSD), psychosis, or Tourette syndrome, according to a report in Lancet Psychiatry.

“Cannabinoids are often advocated as a treatment for various mental disorders,” wrote Nicola Black, Ph.D., of the University of New South Wales and colleagues. Doctors and patients “need to be aware of the low quality and quantity of evidence for the effectiveness of medicinal cannabinoids in treating mental disorders and the potential risk of adverse events,” they added.

Black and colleagues searched several databases including MEDLINE, the Cochrane Central Register of Controlled Clinical Trials, and the Cochrane Database of Systematic Reviews for studies published between 1980 and 2018 that examined changes in symptoms and/or remission following the use of medicinal cannabinoid for treating adults with anxiety, ADHD, depression, PTSD, psychosis, or Tourette syndrome, either as the primary condition or secondary to other medical conditions. The researchers also searched for unpublished or ongoing studies on ClinicalTrials.gov, the EU Clinical Trials Register, and the Australian and New Zealand Clinical Trials Registry.

They identified 83 studies, including 40 randomized, controlled trials (RCTs), for the analysis. Most of the RCTs were very small (with median sample sizes of 10 to 39 participants) and had short follow-up periods (median trial length of four to five weeks), the authors noted.

“We found little evidence for the effectiveness of pharmaceutical CBD [cannabidiol] or medicinal cannabis for the treatment of any of [the examined] mental disorders,” Black and colleagues wrote. “Some very-low quality evidence was found for the use of pharmaceutical THC [tetrahydrocannabinol] (with or without CBD) in treating anxiety symptoms among individuals with other medical conditions, such as chronic noncancer pain and multiple sclerosis.”

In an accompanying commentary, Deepak Cyril D’Souza, M.B.B.S., M.D., of Yale University cautioned, “The process of drug development in modern medicine is to first demonstrate efficacy and safety in clinical trials before using the drug clinically. With cannabinoids, it seems that the cart (use) is before the horse (evidence). If cannabinoids are to be used in the treatment of psychiatric disorders, they should first be tested in randomized, controlled trials and subjected to the same regulatory approval process as other prescription medications.”