Study: Hardly any benefit of cannabis for mental health problems

According to a study published in the journal "The Lancet Psychiatry", no proven benefit was found for post-traumatic stress disorder either, as a research team from the University of Sydney writes. One expert has doubts about the findings.

The researchers drew their conclusion after systematically evaluating data and findings from 54 international clinical trials with a total of 2477 patients, which were conducted between 1980 and 2025. According to the team, this is the largest meta-analysis of its kind on this topic to date.

Possibly slight effects in autism or Tourette's

The team writes that medicinal cannabis products may have some benefit for autism, insomnia or Tourette's syndrome. "But the overall quality of the findings for these conditions is low," emphasizes lead author Jack Wilson. "Without high-quality medical support or adjunctive therapy, the use of medical cannabis in these cases is rarely justified."

Rather, there is a risk that the use of cannabinoids could delay more effective therapies or trigger undesirable side effects. "The routine use of medicinal cannabis could do more harm than good," summarizes Wilson.

Better effect for pain or epilepsy

The situation is different for non-psychiatric conditions: To relieve seizures in some forms of epilepsy, to reduce spasticity in multiple sclerosis or to treat some types of pain, there is certainly a demonstrable benefit of medicinal cannabis, the authors say.

Kirsten Müller-Vahl from the Hannover Medical School, an expert on cannabis in medicine who was not involved in the study, sees weaknesses in the study. For example, the cannabinoids THC (tetrahydrocannabinol) and CBD (cannabidiol) have "very different and sometimes even contradictory effects" on psychosis or anxiety disorders, but are generally evaluated together in the analysis.

According to Müller-Vahl, there are indeed indications that CBD is effective for social anxiety disorders and indications that THC - alone or in combination with CBD - reduces symptoms of post-traumatic stress disorder.

"Another weakness of the review is the mixing of different anxiety disorders. For example, there was a joint evaluation for generalized anxiety disorder and social anxiety disorder," the expert told the German Press Agency. She considers the study's "warning against the use of cannabis-based medication to be unfounded".

In Switzerland, the ban on cannabis for medical purposes was lifted in August 2022.