PARTING: Psilocybin-Assisted suppoRtive psychoTherapy IN the treatment of prolonged Grief; a phase II feasibility safety trial

This psilocybin-assisted psychotherapy intervention involves a combination of pharmacological and psychological treatment. All participants will receive three psychotherapy sessions anticipated to take 1.5 hours each, 1, 2 and 3 days before the 8-hour psilocybin dosing session, then four psychotherapy sessions anticipated to take 1.5 hours, 1 day, then 1, 2 and 4 weeks after the dosing session. The psychotherapy focuses on three distinct phases: (1) Preparation: emphasizing therapeutic alliance, non-avoidance training, psychological and practical preparation for dosing sessions, nature of and relationship to distress, anxiety management strategies, the importance of set and setting, and intention formation; (2) Dosing session: establishing suitable set and setting, non-directive support; (3) Integration: processing what came up in the psilocybin session including any memories of the death and loss (i.e. blocks) and rebuilding by teaching specific strategies in cognitive restructuring to reframe common maladaptive grief-related appraisals (e.g. hopelessness and guilt), communication with the deceased to manage unfinished business and goal setting and/or reintegration into a life that they actually want to live (i.e. beginning the process of making changes to their life following the experience and consider how these may be continued and expanded. The final session will include referral pathways for post-care). The investigational product (Psilocybin Trihydrate [3-[2-(dimethylamino)ethyl]-1H-indol-4-yl] dihydrogen phosphate) will be provided by Cortexa and the dose of the psilocybin capsule used in the study is 25 mg administered orally with water. All participants will be seen by the same two therapists (a clinical psychologist and assistant therapist) in all the psychotherapy sessions and during the psilocybin session. A trial psychiatrist will oversee baseline medical assessments on dose day and be present in the building during the duration of the psilocybin dosing session in case medication and management of any severe adverse events is required. The trial psychologists and assistant therapists are qualified and experienced mental health professionals. The trial therapists, psychiatrist and the lead investigator have undergone professional development training in psilocybin-assisted therapy and prolonged grief therapy order to facilitate this treatment approach safely and successfully. The intervention is supported by a therapy manual developed by the investigator team who are leading experts in psilocybin-assisted psychotherapy and prolonged grief therapy. Moreover, all clinicians on the trial will meet with CI Renee Harvey for ongoing clinical supervision. Descriptive statistics assessing feasibility will include: (i) recruitment rate (enrolled/invited participants); (ii) retention rate (completed seven sessions/enrolled participants); (ii) fidelity to five follow-up questionnaires at 1 day, 6 weeks, 12 weeks, 6 months and 12 months post dosing day (questionnaires completed/active participants). Should participants consent, treatment fidelity will also be monitored via video recordings of all intervention phases. Finally, REDCap session logs will also monitor fidelity to the manualized intervention.