22/09/2026
🍄 A single dose of psilocybin produced rapid reductions in obsessive-compulsive disorder symptoms that lasted for months in a small clinical trial.
Researchers at Yale tested the psychedelic in 28 adults with treatment-resistant OCD.
Participants had lived with OCD for around two decades and had already tried at least two standard treatments without adequate relief.
Fourteen received a single oral dose of psilocybin at 0.25 milligrams per kilogram of body weight, while 14 received niacin, or vitamin B3, as an active placebo.
Just 48 hours later, OCD severity scores in the psilocybin group had fallen by an average of 9.76 points on a standard 40-point scale.
The placebo group showed essentially no change.
One week later, about 69% of those given psilocybin met the researchers’ definition of a clinical response, meaning their OCD symptoms had fallen by at least 35%.
None of the placebo participants reached that threshold.
The improvements also persisted through the 12-week follow-up in some participants.
Scientists are not yet sure how psilocybin produces these effects.
One possibility is that it temporarily increases brain plasticity, making rigid patterns of thought and behaviour easier to disrupt.
But this is still an early study.
Only 28 people participated, and most could probably tell whether they had received a psychedelic or placebo, making true blinding difficult.
One participant with pre-existing suicidal thoughts also developed active suicidal planning during the study, highlighting the need for careful medical supervision.
Psilocybin is therefore not an established treatment for OCD and should not be self-administered.
Still, the trial suggests that a single supervised psychedelic session could produce unusually rapid and potentially lasting relief for some people whose OCD has resisted conventional treatments.
📃 RESEARCH PAPER
📌 Kelmendi et al., “Psilocybin for Treatment-Resistant OCD: A Randomized Controlled Trial”, preprint (2026)
