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Cannabinoids Not Justified as Mental Health Treatment, Study Says

November 04, 2019

A meta-analysis recently published in The Lancet Psychiatry found that using medicinal cannabinoids to treat mental health disorders cannot be justified, due to a lack of evidence of effectiveness and known risks of the substances.

The analysis reviewed 83 studies involving 3000 people from 1980 through 2018. The studies investigated the impact of cannabinoids on remission from and symptoms of 6 mental health disorders: depression, anxiety disorders, attention-deficit hyperactivity disorder, Tourette syndrome, post-traumatic stress disorder, and psychosis. Of the 83 studies, 40 were randomized controlled trials.

Researchers did find “very low quality” evidence that use of tetrahydrocannabinol (THC) may slightly improve anxiety symptoms in people with medical conditions such as chronic pain or multiple sclerosis.

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“Our findings have important implications in countries where cannabis and cannabinoids are being made available for medical use,” said lead author and professor Louisa Degenhardt, PhD, of the National Drug and Alcohol Research Centre at the University of New South Wales, Sydney, Australia.

“There is a notable absence of high-quality evidence to properly assess the effectiveness and safety of medicinal cannabinoids compared with placebo, and until evidence from randomized controlled trials is available, clinical guidelines cannot be drawn up around their use in mental health disorders.”

Patients who are treated with cannabinoids should be carefully monitored for positive and negative mental health effects from them, Dr. Degenhardt said.

In a related commentary, professor Deepak Cyril D'Souza, MBBS, MD, of the Yale University School of Medicine, New Haven, Connecticut, said “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).”

“For cannabinoids to be used in the treatment of psychiatric disorders they should be tested in RCTs and subjected to the same regulatory approval process as other prescription medications,” Dr. D’Souza said.

—Terri Airov


Black N, Stockings E, Campbell G, et al. Cannabinoids for the treatment of mental disorders and symptoms of mental disorders: a systematic review and meta-analysis. The Lancet Psychiatry. 2019 October 28;[Epub ahead of print].

D’Souza DC. Cannabis in psychiatric disorders: the cart before the horse? The Lancet Psychiatry. 2019 October 28;[Epub ahead of print].

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