Lay summary
Major depressive disorders are experienced as recurrent and disabling mental health conditions. Despite the range of pharmacotherapy options, treatment of depression to full symptomatic and functional recovery remains challenging. The most widely used treatment for MDD is antidepressants but one third of patients did not achieve remission. Those who do not achieve remission following multiple treatments have a very poor prognosis which supports the need to examine novel treatment approaches. This study will examine the feasibility and acceptability of integrating psilocybin into interpersonal social rhythms therapy for people with treatment-resistant major depression.