Microdosing Psychedelics to Improve Mood

Inclusion Criteria: Participants must: * Have given written informed consent. * Have a high school level of education. * Be fluent in speaking and reading the study site's predominantly used or recognized language (i.e., English). * Be 18 to 65 years old. * If of childbearing potential, must have a negative pregnancy test at study entry and must agree to use adequate birth control 10 days after the last Experimental Session (refer to section 9.4.2 for contraceptive guidelines). * Have a preexisting diagnosis of MDD with dysthymic subtype or receive a diagnosis of MDD during screening. * Agree that for one week preceding each psilocybin session, they will refrain from taking any nonprescription medication, nutritional supplements, or herbal supplement except when approved by the research team. Exceptions will be evaluated by the research team and will include acetaminophen, non-steroidal anti-inflammatory drugs, and common doses of vitamins and minerals with the exception of SAM-e, 5-HTP, L-tryptophan, and St. John's Wort. * Agree to consume approximately the same amount of caffeine-containing beverage (i.e. coffee, tea) that they consume on a usual morning, before arriving at the research unit on the mornings of psilocybin session days. Caffeine consumption should not exceed more than ≥600mg/day. If the patient does not routinely consume caffeinated beverages, they must agree not to do so on psilocybin session days. * Agree not to take any as needed (PRN) medications on the…