A year after a single psilocybin dose, veterans' depression was still lower than at the start — but the early gains faded, and fewer maintained their response by 12 months.
A 2025 study reported 12-month outcomes for U.S. military veterans with severe treatment-resistant depression who had received a single psilocybin dose.
This 12-month follow-up tracked veterans with severe treatment-resistant depression who had received a single 25 mg dose of psilocybin in an earlier pilot; 10 of the original 15 completed the full year. Their depression stayed lower than baseline throughout, but the strong early gains slipped: at six months about 8 in 10 still had a robust response, and by twelve months that had fallen to about 4 in 10. It's an honest signal about durability — a single dose helped, but for many the benefit did not fully hold over a year without further treatment.
This paper reports 12-month outcomes from an open-label pilot of a single 25 mg psilocybin dose in U.S. military veterans with severe treatment-resistant depression (MADRS). Ten of fifteen participants completed the 12-month follow-up. Depression was significantly reduced from baseline at all timepoints, but scores rose from the short-term timepoints to Month 12. At Month 6, 80% met response and 50% remission; at Month 12, 40% maintained response and 30% remission.
This is a small, open-label pilot with no control group, so the durability data must be read cautiously — there is no way to separate the fading of an active drug effect from natural fluctuation. Attrition is meaningful: only 10 of 15 reached the 12-month mark, and results are for completers. The value here is honesty about durability: unlike a single post-treatment snapshot, this follow-up shows early psilocybin gains waned across the year for a treatment-resistant group.
This extends the first psilocybin trial conducted specifically in U.S. veterans, which reported high response and remission at three weeks (Ellis et al., 2024). A secondary analysis of the same cohort reported improvements in anxiety, quality of life, and functioning (Kelly et al., 2026). The waning pattern echoes open questions across the psychedelic-depression field about whether re-dosing or integration is needed to sustain benefit.
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