A new review suggests psychedelic treatments, particularly psilocybin, may help people with obsessive compulsive disorder (OCD), while cannabis shows little evidence of lasting benefit.
The review, published in the Journal of Psychiatric Research and led by Dr Michael Van Ameringen of McMaster University, examined studies on alternative treatments for OCD, a condition where 40–60% of patients see limited improvement with standard therapies such as SSRIs and behavioural treatment.
After analysing published and preliminary 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. Psilocybin appears to reduce activity in the brain’s default mode network, which is linked to rumination and intrusive thinking and is overactive in OCD. Cannabis, while affecting anxiety-related pathways, does not appear to produce sustained symptom relief.
Researchers also noted differences in treatment approaches. Psychedelic trials often include structured therapeutic support and encourage patients to reflect deeply on their experiences, unlike cannabis studies, which typically focus on symptom relief alone.
Early clinical trial results included in the review showed that a single dose of psilocybin improved OCD symptoms compared with placebo. Further trials are planned to better understand its potential and limitations.
While the findings offer hope, researchers stressed that psychedelics remain difficult to study due to legal restrictions and that more rigorous research is needed. They also cautioned that any potential benefits do not reduce the urgency of carefully controlled, ethical investigation.
