A new study has found that military veterans who attended retreats involving psychedelic substances like psilocybin or ayahuasca experienced substantial short-term improvements in mental health, including symptoms of depression and post-traumatic stress disorder. The study, published in Brain and Behavior, also found that these retreats helped veterans with the often difficult transition back into civilian life.
The researchers set out to explore whether combining psychedelic therapy with communal retreat programs could offer an effective alternative for veterans facing mental health challenges. Veterans returning from combat deployments are at heightened risk for conditions like post-traumatic stress disorder and depression, and many report feelings of isolation and difficulty reintegrating into civilian society.
The study was conducted by researchers in collaboration with Heroic Hearts Project, a nonprofit that connects veterans with psychedelic retreat programs.
“At Heroic Hearts Project, in collaboration with researchers at Imperial College London, we set out to evaluate the impact of psychedelic-assisted retreats as a more accessible and scalable approach to supporting military veterans. Through observational research, we aimed to assess the real-world effectiveness of these naturalistic settings in addressing treatment-resistant PTSD and broader mental health challenges,” said study author Grace Blest‑Hopley, a research associate at King’s College London, chief scientific officer at NWPharma Tech, research director at the Heroic Hearts Project, and founder of Hystelica.
“Importantly, we used validated clinical measures commonly applied in veteran populations—allowing us to compare outcomes against standard benchmarks. We also focused on post-deployment reintegration and the transition from military to civilian life, recognizing this as a critical and often overlooked aspect of veterans’ long-term recovery.”
The research team recruited 58 military veterans who had signed up for either a psilocybin retreat in Jamaica or an ayahuasca retreat in Peru. Participants completed a range of mental health questionnaires before the retreat and again four weeks after returning home. These assessments measured symptoms of PTSD, depression, anxiety, sleep disturbance, post-concussion issues, quality of life, overall well-being, and success in reintegration after military service.
Before being accepted to participate in the retreat programs, all individuals underwent medical and psychological screening to ensure they were physically and mentally stable and not taking medications that might interact negatively with psychedelic substances. They also had to be free from a history of psychotic disorders. Most of the participants were male, in their 40s, and over 80% had a prior PTSD diagnosis. Many had additional diagnoses, including depression, anxiety, and chronic pain. Nearly one-third had never used a psychedelic substance before.
Retreats typically lasted five to seven days. In the psilocybin group, participants drank tea brewed from psychedelic mushrooms in two separate sessions, spaced 48 hours apart. Ayahuasca participants took part in three ceremonies led by indigenous facilitators. Before and after the retreat, participants engaged in group and individual coaching sessions designed to help them prepare for and integrate their experiences. These sessions were a core part of the healing process, encouraging reflection, emotional processing, and connection with fellow veterans.
After four weeks, the researchers found consistent and statistically significant improvements across all eight measured outcomes. The most pronounced effects were seen in depression and PTSD symptoms. On average, depression scores dropped by 29%, while PTSD scores declined by 26%. Participants also showed major gains in anxiety, sleep quality, post-concussion symptoms, and overall mental well-being. Improvements in civilian reintegration were also noted, with an 18% reduction in self-reported difficulties transitioning to post-military life.
“Our study found that psychedelic-assisted retreats can lead to significant early improvements in veterans’ mental health—particularly in depression and PTSD—as well as sleep, anxiety, and overall well-being,” Blest‑Hopley told PsyPost. “Veterans with more severe symptoms often saw the greatest benefit. These results suggest that psychedelic retreats could offer a holistic and scalable approach to supporting veterans, addressing both psychological healing and reintegration into civilian life.”
The researchers also examined how different psychedelic substances and participant characteristics influenced outcomes. Participants who attended psilocybin retreats generally showed greater overall improvement, particularly in measures like depression, anxiety, and post-concussion symptoms. However, veterans who attended ayahuasca retreats saw slightly greater reductions in PTSD symptoms.
Veterans who entered the program with high levels of depression or PTSD experienced the largest drops in their scores four weeks later. This suggests that the retreats may be especially helpful for veterans whose symptoms have not responded well to traditional treatments.
“Veterans with the most severe symptoms showed some of the largest gains,” Blest‑Hopley said. “It underscores the transformative potential of these interventions for those who’ve not responded well to conventional care.”
When the results were broken down by gender, male participants experienced greater improvements across most outcomes—including depression, anxiety, and reintegration—but female participants showed larger reductions in PTSD symptoms. But the researchers noted that the number of women in the study was small, which limits the ability to draw strong conclusions about gender differences.
Despite these encouraging results, the study had several limitations. It was observational in nature and lacked a placebo or control group, which makes it difficult to determine how much of the improvement was due to the psychedelic substances versus other factors, such as the group support or the retreat environment itself. Participants also volunteered for the study and many held positive beliefs about psychedelic therapy beforehand, which may have influenced their responses. In addition, the outcomes were measured only four weeks after the retreat, leaving open the question of whether the benefits would persist over time.
“We can’t disentangle the active psychedelic effect from the therapeutic retreat environment,” Blest‑Hopley noted. “Future randomized studies or control group comparisons are essential.”
The study also did not include data on the specific psychedelic doses administered, nor did it systematically track adverse effects. While the researchers noted that psychedelics are generally considered non-addictive and well-tolerated in clinical settings, the lack of detailed safety data limits the ability to fully assess the risks.
“Our long-term vision is to expand access to psychedelic-assisted retreats for more veterans, grow the healing community, and learn from our collective experiences to inform best practices,” Blest‑Hopley explained. “We aim to conduct meaningful research that helps us understand the real-world impact of these retreats and use that evidence to support advocacy—accelerating access for deserving groups like veterans and their families. Ultimately, we hope this work contributes to a framework for how psychedelic healing can be safely and effectively implemented across the wider population.”
“It’s incredibly encouraging to see such positive outcomes supporting the widespread impact of Heroic Hearts’ work. We remain deeply committed to responsibly expanding access to psychedelics for military veterans—bridging their immediate need for real-world healing with rigorous psychedelic science.”
The study, “Exploring the Therapeutic Effects of Psychedelics Administered to Military Veterans in Naturalistic Retreat Settings,” was authored by Megan Calnan, Grace Blest-Hopley, Chris Busch, Milly Adams, Simon G. D. Ruffell, Theodore Piper, Leor Roseman, Hannes Kettner, and Robin Carhart-Harris.
