CATEGORY: BRAIN & MENTAL HEALTH
For anxiety, the trials found nothing. For post-traumatic stress disorder, nothing. For psychotic illnesses like schizophrenia, nothing. Researchers in Australia pooled every randomized trial ever run on cannabinoids, the active compounds in cannabis such as THC and CBD, as treatments for mental health and addiction, and the most common reasons people reach for these products came up empty.1 For depression, the search found no qualifying trial at all. What the pooled data did show clearly was harm on the side-effect ledger: for roughly every seven people treated, one extra person had an adverse event.
Forty-five years of trials fit inside one small crowd
The review swept five research databases for trials published between 1980 and May 2025 in which chance, not choice, decided who got a cannabis-based treatment and who got placebo. Fifty-four qualified. All of them together enrolled 2,477 people, about the crowd at a small-town football game. That is the entire randomized evidence base behind a product category used by millions, and the reviewers judged nearly half the trials at high risk of bias, rating the certainty of most findings low.
A few conditions showed a flicker
The picture wasn’t uniformly null. Combinations of THC and CBD eased cannabis withdrawal and cut weekly cannabis use in people trying to quit the drug itself. Small trials pointed to fewer tics in Tourette syndrome, longer sleep in insomnia, and reduced traits in autism. Every one of those signals carries the low-certainty label, which means new trials could easily overturn them. One finding ran the wrong way entirely. In people with cocaine addiction, cannabinoids increased craving for cocaine.
Key Takeaways
- Across 54 randomized trials with 2,477 participants, cannabinoids showed no significant benefit for anxiety, PTSD, psychotic disorders, anorexia, or opioid addiction, and no trial has tested them for depression.
- Side effects were more common with cannabinoids: about one additional affected person for every seven treated, though serious adverse events didn’t rise.
- Low-certainty evidence hints at benefit for cannabis withdrawal, Tourette tics, insomnia, and autism traits; the authors conclude routine use for these conditions is rarely justified by today’s data.
References
- Wilson J, Dobson O, Langcake A, et al. The efficacy and safety of cannabinoids for the treatment of mental disorders and substance use disorders: a systematic review and meta-analysis. The Lancet Psychiatry. 2026;13(4):304–315. link