A newly optimised psychological flexibility model adapts Contextual Behavioural Science and Acceptance and Commitment Therapy to the unique challenges of psychedelic-assisted therapy for depression and PTSD, including ego inflation, traumatic memories, and the perceived presence of entities. The model integrates practices and data from psychedelic research into a CBS framework, questioning and adapting psychological flexibility processes to psychedelic contexts. It introduces a Spectrum of Selves model for psychedelic-assisted therapy and examines how to select and retain new self-perspectives and behaviours using evolutionary science principles. A case example and a psychedelic integration checklist guide practical implementation, aiming to increase theoretical-practical coherence, broaden treatment benefits, and reduce relapse.
After a psilocybin truffle retreat, two different psychotherapy interventions—one focused on self-perspective taking and cognitive defusion (ACT-SPT) and another on reexperiencing the psychedelic memory network (ACT-PMNR)—produced different trajectories of change. ACT-PMNR continued to improve participants' anxiety, well-being, and life functioning during the post-psilocybin period, whereas ACT-SPT trajectories drifted back toward baseline. Long-term follow-up of ACT-PMNR showed significant improvements across all measured outcomes, with post-therapy changes exceeding those from the retreat alone. Targeted post-psilocybin psychotherapy may build on initial retreat results, but randomized studies are needed to confirm these findings.