A new review suggests psychedelic treatments may help relieve symptoms of obsessive-compulsive disorder (OCD), while cannabis shows little lasting benefit. The findings come from a study led by Dr Michael Van Ameringen of McMaster University, published in the Journal of Psychiatric Research.
The review found stronger evidence supporting psychedelics such as psilocybin than cannabinoids like THC and CBD. Van Ameringen said up to 60% of OCD patients gain limited relief from existing treatments, prompting interest in alternative options.
Researchers believe the difference lies in how the substances affect the brain. Cannabis acts on CB1 receptors linked to anxiety and compulsions but does not appear to produce durable symptom improvement. Psilocybin, however, reduces activity in the brain’s default mode network, which is heavily involved in rumination and intrusive thinking in OCD.
Preliminary clinical trials, including a Yale study using a single dose of psilocybin, showed symptom improvement compared with placebo. Experts also noted that psychedelic trials often combine medication with therapeutic support, unlike most cannabis studies.
While the results offer cautious optimism, researchers stress that psilocybin remains illegal in many countries and that more rigorous studies are needed before it can be considered a standard treatment.
