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 existing evidence on alternative OCD treatments. It found stronger signals for psychedelics, particularly psilocybin, than for cannabinoids like THC and CBD. This is significant given that 40–60% of people with OCD gain limited relief from standard treatments such as SSRIs and exposure therapy.
Researchers believe the difference lies in how the substances affect the brain. Psilocybin appears to reduce activity in the brain’s default mode network, which is linked to rumination and intrusive thoughts central to OCD. Cannabinoids, while able to ease anxiety or compulsions temporarily, do not seem to produce lasting symptom improvement.
Preliminary clinical trials included in the review showed that a single dose of psilocybin led to greater symptom improvement than placebo. Experts also noted that psychedelic studies typically include structured therapeutic support, unlike most cannabis research, which may influence outcomes.
While the findings offer hope, researchers stress that psilocybin remains illegal in many countries and further rigorous trials are needed. They also caution that any potential benefits do not reduce the urgency of addressing OCD with careful, evidence-based approaches.
