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Post-traumatic stress disorder (PTSD) is highly prevalent among U.S. military Veterans and is often more severe, chronic, and treatment-resistant than in civilian populations. Many Veterans do not respond to first-line psychotherapies or pharmacologic treatments, contributing to substantial impairment and elevated suicide risk. Psilocybin-assisted therapy (PAT) has demonstrated safety and clinical benefit in other populations but has not previously been examined in U.S. military Veterans with PTSD. This study evaluated the safety, feasibility, and preliminary clinical outcomes of PAT in Veterans with severe, treatment-resistant PTSD, a population with urgent unmet mental health needs that are highly relevant to social work research and practice.
Methods
This first-of-its-kind open-label pilot trial enrolled U.S. military Veterans aged 21–64 with DSM-5 PTSD of at least six months’ duration and clinically severe, treatment-resistant symptoms. Twelve participants completed the intervention. The protocol included approximately eight hours of preparatory psychotherapy, two psilocybin dosing sessions (15 mg followed by 25 mg, 2–3 weeks apart), and approximately eight hours of post-dosing integration therapy. Primary outcomes were safety, tolerability, adverse events, and suicidal ideation and behavior from baseline through one-month post-second dosing session. Secondary outcomes included clinician-rated PTSD severity (CAPS-5) and self-reported PTSD symptoms (PCL-5). Exploratory analyses examined symptom change during preparatory therapy and the role of expectancy.
Results
No serious adverse events occurred. Non-serious adverse events were transient and mild to moderate in severity, most commonly headache, anxiety, and dizziness. There was no significant increase in suicidal ideation or behavior during the trial. Clinician-rated PTSD symptoms showed a large and statistically significant reduction from baseline to one-month follow-up (mean difference = 27.5; Cohen’s d = 2.30; p < .001). Seventy-five percent of participants met criteria for both clinical response and remission of PTSD at the primary endpoint. PTSD symptoms also decreased during preparatory therapy, though the largest reductions occurred following psilocybin administration. Expectancy did not significantly predict clinical outcomes.
Conclusions and Implications
In this open-label pilot study, psilocybin-assisted therapy was safe, well-tolerated, and associated with large, clinically meaningful reductions in PTSD symptoms among U.S. military Veterans with severe, treatment-resistant PTSD. These findings provide proof-of-concept that PAT can be delivered safely in this population and support the need for larger, controlled trials. The study is directly relevant to SSWR priorities by addressing mental health inequities among Veterans, evaluating an innovative intervention within a psychotherapeutic framework, and generating evidence with implications for social work practice, clinical service delivery, and future mental health research.