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.
December 30, 2024
Sivert Drange, Jacob Cohen, Sys Stybe Johansen et al.
1 citation
preprint
In a pair of identical twins where one had obsessive-compulsive disorder and the other did not, the affected twin self-administered low, non-psychedelic doses of psilocybin. After the regimen, the affected twin reported a notable reduction in OCD symptoms, improved emotional regulation, and greater well-being. However, cognitive flexibility deficits—the ability to shift thinking—remained compared to the unaffected twin. This suggests that microdosing psilocybin may help relieve some OCD symptoms but does not fully address underlying cognitive impairments. Larger, longer studies are needed to understand how these low doses work and their potential as a treatment.
PsyArXiv
May 14, 2026
Jacob Cohen, Peter Parbo, Per Trads Ørskov et al.
preprint
A double-blind randomized controlled trial will test whether low doses of psilocybin, given alongside virtual reality exposure therapy, can reduce symptoms of social anxiety disorder. The protocol describes the planned methods but does not yet report results.
University of Southern Denmark Research Portal (University of Southern Denmark)
September 9, 2025
Jacob Cohen
Anxiety and trauma-related disorders, including generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and social anxiety disorder (SAD), often respond poorly to conventional pharmacological treatment and psychotherapy. Recent clinical trials suggest that psychedelic substances and ketamine can produce rapid and sustained effects by modulating neural networks responsible for emotion regulation and cognitive flexibility. This dissertation presents five studies examining the therapeutic potential of psilocybin and ketamine across different anxiety-related conditions using clinical and neuroimaging methods.