IMPORTANCE: Psilocybin-assisted psychotherapy may offer a novel approach to treating depression, anxiety, and existential distress in individuals with life threatening illnesses, where current treatments show limited efficacy.
OBJECTIVE: To evaluate the efficacy and safety of psilocybin-assisted psychotherapy versus active placebo and psychotherapy in adults with life-threatening illnesses.
DESIGN: Double-blind, randomized controlled phase 2b trial (RCT) with an open-label extension and 6-month follow-up (January 2020 - October 2023).
SETTING: Single-site study at a tertiary hospital's palliative care department (St. Vincent's Hospital Melbourne affiliated with the University of Melbourne).
PARTICIPANTS: Adults aged 18-80 with a life-threatening illness and clinically significant depression and/or anxiety.
INTERVENTIONS: Participants were randomized to receive 25 mg psilocybin or 100 mg niacin (active placebo), alongside three preparatory psychotherapy and six post-dose integration psychotherapy sessions. After 6-7 weeks post double blind dose, all participants received 25 mg psilocybin in an open-label extension, enabling a two dose versus one dose group comparator. Participants were followed up to 26 weeks post open label dose.
MAIN OUTCOMES AND MEASURES: Primary outcome was change in depression and anxiety symptoms, assessed using the Hospital Anxiety and Depression Scale (HADS), from baseline to 6-7 weeks post-dose. Key secondary outcomes included the Beck Depression Inventory-II (BDI-II) and the State-Trait Anxiety Inventory - State version (STAI-S), which provided complementary, dimensional measures of depression and anxiety over the same time period. Additional secondary outcomes included Death Attitudes Profile, WHOQOL-BREF, State-Trait Anxiety Inventory (STAI-Trait scale), Mystical Experiences Questionnaire, and Persisting Effects Questionnaire. Exploratory outcomes included spiritual well-being, hopelessness, demoralization, and HADS-Trait scores.
RESULTS: Thirty-five participants (mean age 56.0; 54.3 % female) were randomized (psilocybin: n = 17; placebo: n = 18). At 6-7 weeks, psilocybin produced significantly greater reductions in HADS depression (B = -2.49; P = .02; d = 1.12), BDI-II (B = -7.56; P = .004; d = 2.97), and STAI-State anxiety (B = -12.59; P = .005; d = 4.51) compared to placebo. Benefits were sustained at 26 weeks. Exploratory outcomes demonstrated enhanced spiritual well-being, quality of life, and significant reductions in demoralization, death anxiety and hopelessness. No serious treatment-emergent adverse events occurred. Psilocybin was associated with more mild-to-moderate adverse events. One participant withdrew due to anxiety during dosing.
CONCLUSIONS AND RELEVANCE: Psilocybin-assisted psychotherapy appears safe and may offer durable relief from depression and anxiety in individuals with a life-threatening illness.
