A review of alternative treatments for obsessive compulsive disorder (OCD) has found that psychedelic substances, particularly psilocybin, show more promise than cannabis in reducing symptoms.
The review, led by Dr Michael Van Ameringen of McMaster University and published in the Journal of Psychiatric Research, examined published and preliminary evidence on psychedelics and cannabinoids for OCD. It noted that 40–60% of patients gain little or no relief from standard treatments such as SSRIs and exposure therapy.
Researchers found stronger evidence supporting psilocybin than cannabinoids like THC and CBD. Psilocybin appears to affect the brain’s default mode network, which is linked to rumination and intrusive thoughts and is overactive in people with OCD. Cannabinoids, which act on CB1 receptors associated with anxiety and compulsions, did not show lasting symptom improvement.
The review also highlighted differences in study design. Psychedelic trials often include structured psychological support, while cannabis studies typically focus on symptom relief without therapeutic framing. Preliminary clinical trials of psilocybin showed symptom improvement compared with placebo, though further research is needed.
Researchers cautioned that psilocybin remains illegal in many countries, making large-scale trials difficult, and stressed the importance of rigorous, controlled research to better understand its potential role in OCD treatment.
