A new review suggests psychedelic treatments, particularly psilocybin, may help relieve symptoms of obsessive compulsive disorder (OCD), while cannabis shows little evidence of long-term 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 where 40–60% of patients see limited improvement with standard therapies. After analysing published studies and preliminary findings, researchers found stronger evidence supporting psychedelics than cannabinoids such as THC or 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 overactive self-focused thinking in OCD.
Researchers also noted that psychedelic trials typically combine medication with structured therapeutic support, unlike most cannabis studies. Early clinical trials showed psilocybin improved OCD symptoms compared with placebo and helped patients gain insight into their need for control.
The authors cautioned that research remains limited and that psilocybin’s legal status continues to restrict large-scale studies, but said the findings point to promising future treatment options for OCD.
