In a small, uncontrolled trial, 15 veterans with severe treatment-resistant depression received a single 25 mg dose of psilocybin. At three weeks, 60% met criteria for response and 53% for remission. By twelve weeks, 47% maintained response and 40% remission. Co-occurring PTSD did not affect outcomes, and the intensity of the psychedelic experience did not correlate with depression improvement. Four participants who needed to restart antidepressants were counted as non-responders from that point. No unexpected adverse events occurred. The authors note limitations including the small sample and lack of a control group, and call for further study.
Among veterans with severe treatment-resistant depression, a single 25 mg dose of psilocybin produced significant reductions in depression scores that were sustained for up to 12 months, though antidepressant effects began to wane after 6 months and more substantially after 9 months. At 12 months, 40% of 10 participants maintained a response (≥50% reduction in MADRS) and 30% maintained remission (MADRS ≤10). The study was a small, open-label pilot without a control group, so the findings suggest but do not demonstrate lasting benefit.