Comparing Antidepressant Effects of Psilocybin-Assisted Psychotherapy in Individuals That Were Unmedicated at Initial Screening Versus Individuals Discontinuing Medications for Study Participation: Comparaison des effets antidépresseurs de la psychothérapie assistée par la psilocybine (PAP) chez les personnes non médicamentées à la sélection initiale et les personnes ayant arrêté les médicaments pour participer à l’étude

Objective: To compare changes in depression, anxiety, and suicidality symptoms after a single 25 mg oral dose of psilocybin between treatment-resistant depression participants not on antidepressants at screening to participants that discontinued antidepressant medications leading up to receiving psilocybin-assisted psychotherapy (PAP).

Methods: Participants (n = 27) received at least one 25 mg dose of psilocybin accompanied by psychotherapy as part of an exploratory analysis from an open-label, randomized, waitlist-controlled clinical trial. The primary outcome of changes in depression symptoms was measured by the Montgomery-Åsberg Depression Rating Scale (MADRS). Secondary outcomes included changes in anxiety symptom severity (Generalized Anxiety Disorder 7-Item [GAD-7]), suicidal ideation (MADRS Item-10), self-reported depression symptoms (Quick Inventory for Depression Symptomology [QIDS-SR]), and intensity of psychedelic experience (Mystical Experience Questionnaire 30-item [MEQ30]). Patients were separated into two groups for analysis; those who were unmedicated at initial screening versus participants that had to taper off antidepressant medications to be eligible for the trial. A mixed analysis of variance was used to evaluate clinical outcomes over time from baseline to 2 months post-dose.

Results: No significant differences were found between medication discontinued (n = 18) and unmedicated at screening (UAS) (n = 9) groups in clinician rated depression (p = 0.759), self-reported depression (p = 0.215), anxiety (p = 0.178), and suicidality (p = 0.882) symptoms over time, with both groups having clinically significant benefits on all outcomes assessed. Both groups also had a similar intensity of psychedelic experience (p = 0.191).

Conclusion: Comparable improvements were observed in depression and anxiety and symptoms between antidepressant discontinued and UAS patients. These findings contrast with and contribute to the growing literature on the effects of medication tapering leading up to PAP. Further clinical research is needed to directly compare efficacy across medication statuses, in addition to evaluating psychedelic effects in individuals continuing antidepressants during PAP.