Medical Cannabis: Ineffective Against Anxiety and Depression

Unprecedented Study Casts Doubt on Therapeutic Cannabis

Millions of people worldwide use medical cannabis to relieve anxiety, depression, or post-traumatic stress. However, the largest systematic review ever conducted on the subject has just concluded that there is no solid scientific evidence of its effectiveness for these disorders. Published in March 2026 in The Lancet Psychiatry, this meta-analysis comes at a crucial time for France, where the experiment with therapeutic cannabis is coming to an end.

54 Clinical Trials, a Damning Assessment

The team led by Jack Wilson and Emily Stockings, from the University of Sydney (Matilda Centre for Research in Mental Health and Substance Use), analyzed 54 randomized clinical trials conducted between 1980 and 2025, involving approximately 2,500 patients worldwide. The results are clear: cannabis-based drugs—whether they contain cannabidiol (CBD), tetrahydrocannabinol (THC), or a combination of the two—offer no advantage over placebo in treating anxiety, post-traumatic stress, psychotic disorders, anorexia, or opioid-related disorders.

Even more striking: there are no randomized clinical trials specifically on the effectiveness of cannabis against depression, a finding described as "embarrassing" by Ryan Vandrey, a researcher at Johns Hopkins University.

"In the absence of evidence at this stage, the widespread use of medical cannabis for mental health disorders is rarely justifiable"

— Jack Wilson, lead author of the study

Underestimated Risks

Beyond the observed ineffectiveness, the researchers warn of potential risks. A parallel review published in JAMA Internal Medicine identifies significant dangers for adolescents, people predisposed to psychotic or bipolar disorders, and those at risk of addiction. The most common side effects—nausea, dry mouth, fatigue—remain moderate, but the average duration of the trials analyzed was only five weeks, far too short to assess long-term consequences.

Some positive results were nevertheless observed for insomnia, Tourette's syndrome, and certain autism spectrum disorders, but the evidence remains weak. Ziva Cooper, a researcher at UCLA, points out that certain compounds like CBD could have specific benefits that this global review does not allow to distinguish.

A Major Issue for France

These conclusions come at a pivotal moment for France. The national experiment with therapeutic cannabis, launched in 2021 under the aegis of the ANSM (National Agency for Medicines and Health Products Safety), expires on March 31, 2026. No new patients can be included since March 2024, and only patients already treated continue to benefit from care reimbursed by Health Insurance.

A decree framing permanent access to medical cannabis is expected in 2026, with integration into common law planned for late 2026 or early 2027. In parallel, Australia, Germany, Canada, and Brazil already authorize its therapeutic use.

Basing Policies on Science

This study highlights a worrying discrepancy: approximately 27% of adults in the United States and Canada report using cannabis for medical purposes, and nearly half of them do so to manage mental health symptoms. The authors advocate for large-scale, long-term clinical trials, funded independently of the industry, to guide policy decisions on solid scientific grounds rather than on popular perceptions.