A phase 1 study of a second experience with Group Retreat Psilocybin Therapy for partial responders after a first experience
Frontiers in Public Health April 14, 2026 Anthony L. Back, Bonnie A. Mcgregor, Leslie L. Thorn et al.
A second experience of group retreat psilocybin therapy appears safe and feasible for people with metastatic cancer who did not fully benefit from a first session. In a small study of 13 partial responders, the protocol was modified with a higher initial dose (35 mg), an optional 10 mg booster, and no requirement to taper antidepressants. Seven participants received the booster. Anxiety and depression scores improved substantially, with 69% of participants scoring below the clinical threshold at follow-up. The proportion reporting a complete mystical experience rose from 38% after the first session to 77% after the second, without more challenging experiences. Social support and group cohesion also improved and were maintained at 24 weeks.