 This is an interventional, Canadian, multi-site, open-label, single cohort, flexible-dose study. The study will emulate a naturalistic real-life setting. Investigators will include Primary Care Physicians and Psychiatrists working in outpatient clinics. The study will include adult patients diagnosed with MDD according to the DSM-5TM. Approximately 200 patients will be enrolled in the study. There will be approximately 100 patients who receive vortioxetine as a first treatment for the current MDE and 100 patients switched to vortioxetine due to inadequate response to their current antidepressant medication treatment. All patients will be treated with vortioxetine as per the product monograph, and at the doses determined appropriate by the investigator. The total study duration from Baseline to the end of follow-up will be approximately 56 weeks. 