Value of Medical Marijuana for Mental Health Questioned

A meta-analysis of more than 80 studies from the past four decades finds weak evidence to support the use of medicinal cannabis to treat anxiety, depression, and other mental health disorders.

Written byJef Akst

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So far, research has failed to provide convincing evidence of the efficacy of medicinal cannabis treatments to alleviate symptoms associated with mental illnesses such as anxiety, depression, attention-deficit hyperactivity disorder, Tourette syndrome, post-traumatic stress disorder, or psychosis, according to a meta-analysis published in The Lancet Psychiatry yesterday (October 28).

The study, which examined 83 studies since 1980 involving a total of more than 3,000 people, also found concerns with the use of medical marijuana treatments that include the main psychoactive ingredient of cannabis, delta-9-tetrahydrocannabinol (THC). One 2005 study of 24 patients, for example, found that a treatment that included THC worsened the negative symptoms of psychosis and reduced cognitive functioning compared with placebo. And looking across nearly a dozen randomized controlled trials, other THC-based therapies led to more adverse side effects compared with placebo, and more patients withdrew from the study as a result.

“Cannabinoids are ...

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Meet the Author

Jef Akst
Jef (an unusual nickname for Jennifer) got her master’s degree from Indiana University in April 2009 studying the mating behavior of seahorses. After four years of diving off the Gulf Coast of Tampa and performing behavioral experiments at the Tennessee Aquarium in Chattanooga, she left research to pursue a career in science writing. As The Scientist's managing editor, Jef edited features and oversaw the production of the TS Digest and quarterly print magazine. In 2022, her feature on uterus transplantation earned first place in the trade category of the Awards for Excellence in Health Care Journalism. She is a member of the National Association of Science Writers.
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