Ohio State pilot trial: 9 of 12 veterans with severe, treatment-resistant PTSD in remission one month after psilocybin-assisted therapy

Researchers at The Ohio State University have published the first US clinical trial of psilocybin-assisted therapy in veterans whose PTSD had not responded to conventional treatment. The open-label pilot, led by Stacey Armstrong of Ohio State's Center for Psychedelic Drug Research and Education, appeared in Communications Medicine on 30 July 2026.

Key findings

• Safety: no serious adverse events and no increase in suicidal thinking or behaviour across the 11-week protocol.
• Symptom reduction: clinician-rated PTSD symptoms on the CAPS-5 scale fell by an average of 27.5 points from baseline to one month after treatment, from close to 40 to just over 12.
• Remission: nine of the twelve veterans (75%) no longer met criteria for PTSD one month after the study ended.

How the trial was run

Participants received about eight hours of preparatory psychotherapy, then two supervised psilocybin sessions of 15 mg and 25 mg spaced two to three weeks apart, followed by roughly eight further hours of integration therapy. Recruitment ran from January 2023 to April 2025.

Limitations

This was a small, open-label study with no control group, so expectancy effects cannot be separated from drug effects, and results in twelve people can shift substantially in larger samples. The authors describe the outcomes as preliminary. A randomised, controlled follow-up is the necessary next step; the VA's newly announced PIVOT trial will provide controlled data in a related population.

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