Psychedelic treatments such as psilocybin may offer relief for people with obsessive-compulsive disorder (OCD), while cannabis appears ineffective, according to a new review published in the Journal of Psychiatric Research.
The review, led by Dr Michael Van Ameringen of McMaster University, examined alternative treatments for OCD, a condition for which 40–60% of patients gain little or no benefit from standard therapies such as SSRIs and exposure therapy. After analysing published studies, conference data and preliminary findings, the researchers found stronger evidence supporting psychedelics than cannabinoids like THC and CBD.
Van Ameringen suggested the difference may lie in how the substances affect the brain. Cannabinoids act on CB1 receptors linked to anxiety and compulsive behaviour but do not appear to provide lasting symptom relief. Psilocybin, by contrast, reduces activity in the brain’s default mode network, which is associated with rumination and intrusive thoughts and is overactive in OCD.
Preliminary clinical trials, including work by researchers at Yale University, showed that a single dose of psilocybin reduced OCD symptoms compared with placebo. Researchers also observed that patients gained insight into their need for control, a central feature of the disorder.
The authors stressed that while the findings are promising, psilocybin remains illegal in many countries, making research difficult. They also cautioned that more large-scale, controlled trials are needed before psychedelics can be considered a standard treatment for OCD.
