Veterans With Traumatic Brain Injuries (TBI) Show Mental Health Gains, Reflected in EEG Scans, After Psilocybin Retreat (2025)
August 2025 / Paper authors:
Grace Blest-Hopley Giuseppe Pasculli Simon G. D. Ruffell WaiFung Tsang Olateju Emmanuel Kathryn M. Pate Hannes Kettner Leor Roseman David Erritzoe Robin Carhart-Harris
Improved mental health outcomes and normalised spontaneous EEG activity are shown in veterans reporting a history of traumatic brain injuries (TBI) following participation in a psilocybin retreat, in new research published in Frontiers of Psychiatry.
This is the latest publication from Onaya Science in our cherished ongoing collaboration with Heroic Hearts Project and the Italian Society for Psychedelic Medicine (SIMEPSI),
Traumatic Brain Injury (TBI): Becoming a research priority for Onaya Science
Military veterans face elevated risks of traumatic brain injury (TBI) – a complex neurological condition frequently accompanied by mental health challenges – due to repeated exposure to concussive forces during service.
Previous evidence has shown psychedelics may offer significant improvements in mental health outcomes for veterans (29,30) but there remains a critical gap in understanding how these compounds affect symptoms specifically linked to head trauma.
An observational study, dedicated to participants with a history of TBI
This observational study recruited 21 male veterans (mean age = 38.5 years) with a history of traumatic brain injury (TBI) and current psychological distress. Participants attended a six-day psilocybin retreat in Jamaica, which included two ceremonial sessions involving controlled doses of psilocybin (1.5g–5g).
A mixed-methods approach to assessing psilocybin’s impact on TBI
All participants underwent structured psychological preparation prior to the ceremonies. A comprehensive battery was administered pre- and post-retreat, including:
Psychological and behavioural measures including PTSD checklist (PCL-5), Patient Health Questionnaire (PHQ-9) for depression, State-Trait Anxiety Inventory (STAI), and the Rivermead Post-Concussive Questionnaire (RPQ)
Neurophysiological assessments including resting state EEG data
Reduced depression scores, anxiety and post-concussive symptoms among the improvements seen
Results demonstrated significant improvement across key mental health and wellbeing measures, including depression (PHQ-9), anxiety (STAI), post-concussive symptoms (RPQ), and military-to-civilian adjustment (M2C), suggesting psilocybin may help alleviate subjective symptoms associated with TBI.
Surprising finding?
Psychedelic history tied to stronger therapeutic outcomes
When participants were stratified by prior psychedelic experience – despite both showing a trend towards improvement – only those with previous exposure to psychedelics achieved statistically significant changes across outcomes, suggesting prior experience may enhance therapeutic responsiveness.
"This is an exciting finding, but it’s important to remember that positive outcomes likely reflect multiple interacting factors, not just prior psychedelic experience. We’re interested in exploring how elements such as preparation, integration, and the supportive community around the ceremony could be made accessible in daily life, helping all participants benefit regardless of prior experience.”
(Dr Simon Ruffell, Onaya Science Co-Founder)
Emotional regulation and memory integration supported by psilocybin, neuroimaging findings indicate
Neurophysiological findings aligned with the study’s hypothesis and existing literature on EEG abnormalities in TBI. Participants exhibited reduced delta power (typically elevated in chronic TBI and associated with cortical dysfunction) alongside normalised theta activity, which is linked to emotional regulation and memory integration. Alpha and beta bands showed modulation consistent with improved thalamocortical function and cognitive control. Additionally, increased connectivity in frontal and central brain regions suggested enhanced neural communication and integration following psilocybin administration.
The Onaya Science take: Context, and not psilocybin alone, is a key component of these results
Importantly, the study’s design does not allow for definitive attribution of outcomes to psilocybin alone. Improvements may have been influenced by nonspecific factors such as natural recovery, psychological support, group dynamics, or expectancy effects inherent to the retreat setting. To isolate the effects of psilocybin, future studies should employ larger samples and more rigorous controls, ideally using double-blind, placebo-controlled designs.
Further research is also needed to explore the underlying mechanisms of psilocybin’s effects in TBI populations. One promising avenue involves investigating its potential anti-inflammatory properties, given the well-established role of neuroinflammation in TBI pathophysiology.