Medicinal cannabis not proven in mental health, study finds

Grant Boone
October 31, 2019

(CBD is a compound derived from marijuana that does not produce a "high.") Both mainstream media and the commercial sector have hopped on the bandwagon, spreading the word about the many potential therapeutic uses of cannabinoids. This spring, Google searches for CBD exceeded searches for buzzy health topics like acupuncture, apple cider vinegar and meditation, according to a recent JAMA Network Open analysis.

The use of cannabis medicines to treat people with depression, anxiety, psychosis or other mental health issues can not be justified because there is little evidence that they work or are safe, The Guardian reports citing a major new study.

The authors set out to examine the available evidence for all types of medicinal cannabinoids.

The authors found that pharmaceutical THC (with or without CBD) improved anxiety symptoms among individuals with other medical conditions (seven studies of 252 people), though this may have been due to improvements in the primary medical condition.

It also increased the number of people who reported side effects, and the number who made a decision to withdraw from a study due to side effects.

The research analysed 83 studies of around 3,000 people between 1980 and 2018.

There is inadequate evidence that cannabinoids relieve depression, anxiety disorders or attention-deficit hyperactivity disorder, scientists have said.

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In addition, research suggests that repeated or heavy cannabis use can permanently disrupt the body's natural "endocannabinoid system", which produces chemicals that bind to the same receptors as cannabinoids do, though how this disruption affects people with different mental health disorders remains under investigation.

Despite a lack of clinical trial evidence, anecdotally some military veterans and others who suffer post-traumatic stress disorder (PTSD), depression and anxiety say they have found cannabis helpful in easing some of their symptoms. "This research suggests that cannabis use can increase the occurrence of depression, anxiety, and psychotic symptom", says the paper. In one small study of patients with psychosis, pharmaceutical THC - the active substance in cannabis - actually worsened symptoms. Countries that allow medicinal cannabinoid use will probably see increased demand for such use. The study found that after chronic non-cancer pain, mental health is one of the most common reasons for using medicinal cannabinoids.

They highlight that their analysis and conclusions are limited by the small amount of available data, small study sizes, and the differences in findings between small studies. They also note that most studies are based on pharmaceutical cannabinoids, rather than medicinal cannabis, but plant products are most often used by those taking cannabinoids for medicinal purposes in the USA.

"In light of the results of this comprehensive review and meta-analysis, it would be hard for practitioners to justify recommending the use of cannabinoids for psychiatric conditions at this time", Dr. Deepak Cyril D'Souza, a professor of psychiatry at Yale University School of Medicine, wrote in a commentary accompanying the new study.

Dr. Scott Krakower, assistant unit chief of psychiatry at Zucker Hillside Hospital in Glen Oaks, New York, who was not involved in the study, told Live Science that the idea that cannabis may worsen certain mental health disorders is well-established. With cannabinoids, it seems that the cart (use) is before the horse (evidence).

A press release for this report is also available.

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