Psilocybin therapy for adult females with anorexia nervosa: pilot study.

Background: Anorexia nervosa is a debilitating eating disorder with high mortality and chronicity rates owing to the paucity of effective existing treatments. Several clinical trials using psilocybin therapy have demonstrated therapeutic efficacy and safety in psychiatric conditions, including anorexia nervosa.

Aims: This study aimed to further assess the safety, feasibility and potential efficacy of psilocybin therapy in anorexia nervosa.

Method: This single-blind, within-individual pilot study recruited 21 females with anorexia nervosa, who underwent three dosing sessions with oral psilocybin (COMP360) over 6 weeks in a fixed order (1 mg, 25 mg, 25 mg), alongside talk therapy and adjunctive to treatment as usual. Adverse events were monitored throughout the study. Primary clinical outcome measures were global Eating Disorder Examination Interview (EDE) and Readiness and Motivation Questionnaire (RMQ) precontemplation scores. Primary time points for the EDE were the 6-week final visit, 3-month follow-up and 6-month follow-up; and for the RMQ, they were the 6-week final visit and comparison between dosing days. Global EDE Questionnaire scores were a key secondary outcome. Key time points were the 6-week final visit and comparison between dosing days. There was a 12-month remote follow-up.

Results: Psilocybin was well tolerated by all participants. The most common adverse events were headache, nausea and dizziness. Two serious adverse events (suicide attempts) were reported for one participant within the 6–12-month period. Relative to baseline, participants displayed significant improvements in their eating disorder symptoms (EDE scores: p < 0.0001, d = 0.98, 6 months) and motivation to change (RMQ scores: p = 0.0017, d = 0.65, 12 months). However, there was a large variation in improvement and maintenance during the follow-up.

Conclusions: This study further provides preliminary support for the feasibility, safety and potential efficacy of this intervention to treat adult females with anorexia nervosa, and warrants further investigation in larger and more rigorously designed studies.