Case Report: Repeated low doses of psilocybin reduce perceived symptom severity but fail to restore cognitive flexibility in a case of severe obsessive-compulsive disorder: an observational case study of identical twins.
Frontiers in psychiatry January 1, 2026 Sivert Drange, Jacob Cohen, Sys Stybe Johansen et al. 1 citation
In identical twins discordant for obsessive-compulsive disorder, the affected twin self-administered low doses of psilocybin (1–5 mg every third day) while the unaffected twin did not. The affected twin reported notable reductions in OCD symptoms, improved emotional regulation, and better well-being. However, cognitive flexibility, measured with a set-shift task, remained impaired compared to the unaffected twin. Low-dose psilocybin may alleviate some OCD symptoms but does not fully address underlying cognitive deficits.