Skip to content

Exploring the Therapeutic Effects of Psychedelics Administered to Military Veterans in Naturalistic Retreat Settings

Megan Calnan, Grace Blest‐hopley, Chris Busch, Mark J. Adams, Simon Ruffell, Theodore Piper, Leor Roseman, Hannes Kettner, Robin Carhart-Harris

Brain and Behavior July 1, 2025 DOI: 10.1002/brb3.70660 (opens in new tab)

Study at a glance

AI-extracted from the abstract
Characteristics Observational cohort Peer reviewed
Sample size 58
Population Military veterans
Interventions Psilocybin Ayahuasca
Duration Up to 4 weeks pre- and post-retreat
Topics Anxiety Ayahuasca Psilocybin
Keywords Mental health Depression economics Patient health questionnaire Clinical psychology Hallucinogen Psychotherapist Depressive symptoms
Citations 4
Key findings Psilocybin and ayahuasca retreats significantly improved veterans' mental health and community reintegration, with the greatest improvements in depression and PTSD, and larger benefits for those with more severe initial symptoms.

Abstract

Abstract Background : Military veterans are at risk of various mental health conditions, with profound implications for post‐deployment quality of life. Current treatment options encounter high dropout rates and non‐responsiveness, and overlook the importance of community building in veterans’ holistic recovery. Preliminary research suggests psychedelics offer therapeutic benefits for depression and post‐traumatic stress disorder (PTSD) in veterans. Integrating psychedelic therapies with a communal retreat setting could provide a more holistic framework for improving veterans’ well‐being. Objectives : To evaluate the effects of psychedelic retreats on mental health and community reintegration in veterans. Methods : Fifty‐eight veterans attended psilocybin or ayahuasca retreats. Participants completed eight mental health questionnaires (e.g. PTSD Checklist, PCL‐5; Patient Health Questionnaire, PHQ‐9), and the Military to Civilian Questionnaire (M2C‐Q) up to 4 weeks both pre‐ and post‐retreat. Paired t ‐tests analyzed changes in outcome responses between time points, and gender and substance‐specific analysis was conducted. Baseline scores were correlated with improvements in PCL‐5 and PHQ‐9 to investigate the relationship between initial symptom severity and percentage improvement following the retreat. Results : Significant improvements were found for all eight outcomes post‐retreat, with the greatest percentage improvements found for depression (PHQ‐9; 29.1%) and PTSD (PCL‐5; 26.1%). Veterans attending psilocybin retreats showed greater improvements in seven out of eight outcomes, whereas ayahuasca retreats demonstrated greater improvements in PCL‐5 scores for PTSD (ayahuasca: 26.4%; Psilocybin 24.8%). Male participants experienced greater improvements across all outcomes apart from the PCL‐5 for PTSD (Male: 24.1%; Female: 32.1%). Higher baseline scores on the PCL‐5 (PTSD) and PHQ‐9 (depression), indicating worse initial mental health, correlated with greater outcome improvements. Conclusions : This is the first study to investigate psychedelic retreats as a holistic therapy for veterans’ mental health alongside community reintegration. Psilocybin and ayahuasca retreats significantly improved veterans’ mental well‐being, quality of life, PTSD, anxiety, depression, sleep, concussion, and post‐deployment reintegration. Participants with more severe symptoms have the potential to benefit most from this intervention, with nuanced insight into improved outcomes based on gender and type of substance. Psychedelic retreats could provide a treatment framework to aid veterans’ recovery by addressing psychological well‐being, communal factors, and reintegration into civilian life.

In the evidence

This study is part of the evidence base for a synthesis in the library. Here is how each one recorded it.

  • Psilocybin and ayahuasca retreats significantly improved veterans' mental health and community reintegration, with the greatest improvements in depression and PTSD, and larger benefits for those with more severe initial symptoms.

    Synthesized

Comparable studies

Other observational and cohort studies on ayahuasca for anxiety, most cited first.

Study Year Design Participants
Antidepressant effects of a single dose of ayahuasca in patients with recurrent depression: a preliminary report Patients with a depressive disorder 2015 Observational study
Ayahuasca’s ‘afterglow’: improved mindfulness and cognitive flexibility in ayahuasca drinkers Ayahuasca drinkers (both naïve and experienced) 2020 Observational study
A placebo-controlled study of the effects of ayahuasca, set and setting on mental health of participants in ayahuasca group retreats Experienced participants of ayahuasca retreats in the Netherlands, Spain, and Germany 2021 Naturalistic observational study n = 30
Persisting Effects of Ayahuasca on Empathy, Creative Thinking, Decentering, Personality, and Well-Being Volunteers attending ayahuasca ceremonies 2021 Naturalistic observational study n = 43
Ceremonial Ayahuasca in Amazonian Retreats—Mental Health and Epigenetic Outcomes From a Six-Month Naturalistic Study Self-selected participants in ayahuasca ceremonies at a retreat centre in the Peruvian... 2021 Prospective naturalistic study n = 63

Explore topics

By condition and practice