Psilocybin for Treatment-Resistant Depression

The purpose of this study is to see if psilocybin, an investigational drug, is safe and well tolerated. Researchers also want to know if psilocybin can improve symptoms of depression. This study will see if psilocybin is safe and well tolerated by tracking changes in suicidal thoughts and behaviour, monitoring if any participants choose to stop participating in the study, and measuring any serious side effects, as well as how long they take to resolve. This study will also see if depression symptoms improve (or worsen) after psilocybin is administered. Additional information about participants' depressive symptoms and side effects will also be measured during the study.