A pilot study of the effect of group-administered psilocybin on psychological flexibility and outcomes

Abstract Psychological flexibility has been proposed as a core process of change when psychedelics are used for therapeutic purposes, but to date empirical outcomes have only documented changes on the Acceptance and Action Questionnaire (AAQ-II), a very general measure of psychological flexibility. This pilot study measured outcomes from psilocybin administered in a retreat setting across a range of measures assessing aspects of psychological flexibility. Nine participants attended a 7-day psilocybin retreat and completed measures at baseline, 2-, and 6-month follow up. Participants demonstrated significant improvements in cognitive defusion (Cognitive Fusion Questionnaire), valued living (Valuing Questionnaire), and Self-Compassion (Self-Compassion Scale), as well as a trend towards increased overall psychological flexibility (AAQ). Other outcome and process measures included measures related to acute effects of the psilocybin, belief in oneness, social safeness, mental health, burnout and emotion expressivity. These results offer preliminary evidence that therapeutic benefits obtained from psilocybin experiences may be linked to changes in psychological flexibility.