PET Synaptogenesis After Psilocybin In DEpression Recovery

The investigators are studying the neurotrophic effects of psilocybin using 11C-UCB-J, a PET marker for synaptogenesis. Psilocybin is a naturally occurring psychedelic and exerts perceptual effects via 5-HT2A receptor agonism. Psilocybin has gained a great deal of attention as a tool for psychiatric treatment, with clinical trials demonstrating symptom relief after a single dose that is immediate and persists for months. Recognizing the therapeutic potential of psilocybin, the US Food and Drug Administration granted breakthrough therapy status to the Usona Institute for Phase 2 testing of psilocybin in depression. Animal models suggest that psychedelics exert antidepressant effects by producing a rapid and powerful neurotrophic response in the brain. The investigators will enroll patients with major depressive disorder and anhedonia. Participants will be given a single dose of psilocybin and supportive psychotherapy before, during, and after drug administration. Participants will undergo PET imaging before and one week after drug using 11C-UCB-J, a radiotracer that binds to SV2A - a marker of synaptic density and synaptogenesis. This design allows the investigators to assess the relationship between neurotrophic, and antidepressant effects produced by psilocybin.