1. Has a primary diagnosis of major depressive disorder (MDD), without psychotic features, according to Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM 5) criteria, as assessed by a board-certified psychiatrist. MDD should be the principal diagnosis and the condition that best accounts for the clinical presentation. Participants with a secondary diagnosis of generalized anxiety disorder or social anxiety disorder may be included if, in the principal investigator's judgment, such diagnosis will not interfere with participation in the study or with outcome assessments. The diagnostic assessment must include a face-to-face evaluation of the participant using the Mini International Neuropsychiatric Interview (MINI).