Psilocybin-Assisted Therapy in Treatment-Resistant Depression

The goal of this clinical trial is to test how well psilocybin-assisted therapy works in treating people with depression. The main questions this study aims to answer are: * Does psilocybin with assisted therapy help improve symptoms for people with depression? * How long do the effects of this treatment last? Participants will: * Take part in a couple of screening and preparation visits. * Be given psilocybin in one or two treatment sessions. * Attend a series of follow-up sessions over the following year. * Complete forms and surveys to test how their symptoms have changed and what they thought of their experience. Researchers will also compare whether one treatment or two treatments help improve symptoms more for participants.