Microdosing Psychedelics to Improve Mood

This protocol is for a University of Toronto - sponsored, randomized, placebo-controlled crossover phase 2 study of the safety and efficacy of low doses of psilocybin in subjects with depressive symptoms who meet Diagnostic and Statistical Manual 5 (DSM-5) criteria for diagnosis of a major depressive disorder (MDD) and who are either unwilling to pursue standard treatment (psychotherapy and/or pharmacotherapy) or have previously been non-responsive to standard treatment. This feasibility study will assess whether microdosing has a short-term impact on participant ratings of depressive symptoms. Participants will be administered one dose of either placebo or psilocybin once weekly for four weeks, and then all participants will be administered a dose of psilocybin once weekly for four additional weeks. Short surveys will be collected once weekly three days after the administration of psilocybin/placebo, and follow-ups will occur for up to two years following the beginning of the trial. Using this design will maximize the experimental power to detect an effect if one exists and would inform future research on microdosing in terms of duration, effect size, and expectancy bias.