Presynaptic Imaging in Major Depressive Episodes After COVID-19

Inclusion Criteria: * New onset MDE within 3 months after mild or moderate COVID-19, with MDE verified by the research version SCID for DSM 5. See "Positive COVID-19 diagnosis" listed after inclusion/exclusion criteria for a description of how this is determined. * Age 18 to 75. * Good general physical health with no active medical conditions based on self-report (except migraine or PASC). Exclusion Criteria: * Use of antidepressants in the previous month (6 weeks for fluoxetine). * Use of stimulant medication affecting dopamine release in the previous month * Use of antipsychotics in the previous month * History of neurological disease (except migraine, and PASC) based on self-report * Use of medications or herbal products or natural health products with central nervous system effects in past 2 weeks based on self-report * Presence of cigarette smoking in the past two months, based on self-report * Lifetime diagnosis of severe Substance or Alcohol Use Disorder, or diagnosis of mild to moderate Substance or Alcohol Use Disorder in the past two years, based on self-report and verified by the Research Version of Structured Clinical Interview for Diagnostic and Statistical Manual-5 (SCID-5-RV) * Use of recreational drugs, including marijuana, in the past two months, based on self-report and verified by the Research Version of Structured Clinical Interview for Diagnostic and Statistical Manual-5 (SCID-5-RV) * Positive urine drug or cotinine screen at any timepoint during the study * History of psychotic symptoms secondary to schizophrenia, schizophreniform, bipolar disorder, or brief psychotic disorder prior to COVID-19, based on self-report and verified by the Research Version of Structured Clinical Interview for Diagnostic and Statistical Manual-5 (SCID-5-RV) * Currently pregnant, based on self-report or positive pregnancy test at any timepoint during the study, in females (in our PET Centre females up to 65 years of age are given a urine pregnancy test prior to every PET scan) * Breastfeeding (for females) * Current disorders of coagulation, blood or ongoing use of anticoagulant medication, based on self-report * Claustrophobia, based on self-report * Weight over 400lbs and height over 7ft (requirements for fitting in the scanners and hospital gowns) * Presence of metal implant, object or electrical devices that are contraindicated for MRI, based on self-report * Severe allergic reaction to alcohol