The Music for Subanesthetic Infusions of Ketamine randomised clinical trial: ketamine as a psychedelic treatment for highly refractory depression

Background Ketamine exerts potent but transient antidepressant effects in treatment-resistant depression (TRD). Combinations of ketamine and psychotherapy have attracted interest, but no trial has investigated a psychedelic model of ketamine-psychotherapy for TRD to our knowledge. Aims This secondary analysis of a randomised clinical trial (RCT) explores the therapeutic effects and experiential mechanisms of the Montreal Model of ketamine-psychotherapy for TRD, with or without music. Method A two-centre, single-blinded, RCT conducted in Montreal, Canada, between January 2021 and August 2022 (NCT04701866). Participants received ketamine-psychotherapy for TRD - six subanaesthetic infusions over 4 weeks and psychological support - with either music or matched non-music support during ketamine doses, as per random group assignments. The primary therapeutic outcome was the Montgomery-Åsberg Depression Rating Scale, assessed by blinded raters. Psychedelic-like experiences, evaluated by the Mystical Experience Questionnaire and Emotional Breakthrough Inventory, and their session-by-session relationships with depression were explored with multilevel, time-lagged covariate models with autoregressive residuals. Results Thirty-two participants with severe and highly comorbid TRD, including high rates of personality disorder and suicidality, received 181 ketamine infusions. Therapeutic outcomes and psychedelic experiences did not differ between music ( n = 15) and non-music ( n = 17) interventions. Both groups experienced significant reductions in clinician-rated and self-reported depression ( d = 1.2 and d = 0.87, respectively; p < 0.001), anxiety ( d = 0.8, p < 0.001) and suicidality ( d = 0.4, p < 0.05) at 4 weeks, fully maintained at 8-week follow-up. Ketamine experiences were highly emotional and mystical. Converging analyses supported mystical-like ketamine experiences as mechanisms of its antidepressant effects. Conclusions This trial found large and notably sustained benefits of ketamine-psychotherapy for severe TRD, with or without music, and psychedelic experiences of comparable intensity to those observed with psilocybin. Mystical-like experiences may particularly contribute to ketamine’s immediate and persistent psychiatric benefits.