Safety and Efficacy Study of Vortioxetine (Lu AA21004) in Adults With Major Depressive Disorder

Inclusion Criteria: * Suffers from a major depressive episode (MDE) recurrent as the primary diagnosis according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) criteria. * The reported duration of the current MDE is at least 3 months. * Has a Montgomery Åsberg Depression Rating Scale (MADRS) total score of 26 or greater at Screening and Baseline Visits. * Has a Clinical Global Impression - Severity of Illness (CGI-S) score of 4 or greater at Screening and Baseline Visits. Exclusion Criteria: * Has received any investigational compound \<30 days before Screening or 5 half-lives prior to Screening. * Has received Lu AA21004 in a previous clinical study. * Has 1 or more the following: 1. Any current psychiatric disorder other than MDD as defined in the DSM-IV-TR . 2. Current or history of: manic or hypomanic episode, schizophrenia or any other psychotic disorder, including major depression with psychotic features, mental retardation, organic mental disorders, or mental disorders due to a general medical condition as defined in the DSM-IV-TR. 3. Diagnosis of alcohol or other substance abuse or dependence (excluding nicotine or caffeine) as defined in the DSM-IV-TR that had not been in sustained full remission for at least 2 years prior to Screening. 4. Presence or history of a clinically significant neurological disorder (including epilepsy). 5. Neurodegenerative disorder (Alzheimer disease, Parkinson disease, multiple sclerosis, Huntington disease, etc). 6. Any Axis II disorder that might compromise the study. * The current depressive symptoms of the patient were considered by the investigator to have been resistant to 2 adequate antidepressant treatments of at least 6 weeks duration each. * Has received electroconvulsive therapy, vagal nerve stimulation, or repetitive transcranial magnetic stimulation within 6 months prior to Screening. * Was currently receiving formal cognitive or behavioral therapy, systematic psychotherapy, or planned to initiate such therapy during the study. * Has a significant risk of suicide according to the investigator's clinical judgment or had a score ≥5 on item 10 (suicidal thoughts) of the MADRS or had made a suicide attempt in the previous 6 months. * Was required to take excluded medications or it was anticipated that would require treatment with at least 1 of the disallowed concomitant medications during the study. * Has a clinically significant unstable illness, for example hepatic impairment or renal insufficiency, or a cardiovascular, pulmonary, gastrointestinal, endocrine, neurological, rheumatologic, immunologic, hematological, infectious, dermatological disorder or metabolic disturbance. NOTE: For the purposes of this study, the following conditions were considered unstable due to the potential impact on assessment of MDD response: pain disorder, chronic fatigue syndrome, fibromyalgia, and obstructive sleep apnea. * Has 1 or more laboratory value outside the normal range, based on the blood or urine samples taken at the Screening Visit, that were considered by the investigator to be clinically significant; or the patient has any of the following values at the Screening Visit: 1. A serum creatinine value \>1.5 times the upper limits of normal (× ULN). 2. A total serum total bilirubin value \>1.5 × ULN. 3. A serum alanine aminotransferase (ALT) or aspartate aminotransferase (AST) value \>2 × ULN. * Has a thyroid stimulating hormone value outside the normal range. * Has clinically significant abnormal vital signs. * Has an abnormal electrocardiogram.