A new review suggests psychedelic treatments such as psilocybin may help people with obsessive compulsive disorder (OCD), while cannabis-based treatments show little benefit.
The review, led by Dr Michael Van Ameringen of McMaster University and published in the Journal of Psychiatric Research, examined alternative treatments for OCD, a condition in which 40–60% of patients gain limited relief from standard therapies. After analysing published studies and preliminary trial data, researchers found stronger evidence supporting psychedelics than cannabinoids like THC and CBD.
Van Ameringen said the difference may lie in how the substances affect the brain. Cannabis activates CB1 receptors linked to anxiety and compulsions but does not appear to provide lasting symptom relief. Psilocybin, however, reduces activity in the brain’s default mode network, which is associated with rumination and intrusive thoughts and is overactive in OCD.
Early clinical trials included in the review showed that a single dose of psilocybin improved OCD symptoms compared with placebo. Researchers also noted that psychedelic trials often combine medication with guided therapeutic support, which may contribute to their effectiveness.
While the findings offer hope for new OCD treatments, researchers stressed that psilocybin remains illegal in many countries, making large-scale trials difficult, and that further rigorous research is needed.
