PURPOSE: To describe pharmacological treatment patterns in Asian patients with major depressive disorder (MDD), including duration of treatment, reasons for medication discontinuation, rate of medication nonadherence, factors associated with medication nonadherence, and impact of medication nonadherence on depression outcomes. PATIENTS AND METHODS: Data were from a prospective, observational 3-month study of East Asian MDD inpatients from 40 sites in six East Asian countries who initiated antidepressant treatment at baseline (n=569). Assessments included the Clinical Global Impression-Severity scale (CGI-S), 17-item Hamilton Depression Rating Scale (HAMD-17), painful physical symptoms, response and remission, employment status, quality of life (QoL) (EuroQOL Questionnaire-5 Dimensions [EQ-5D]) and health state using the visual analog scale, adherence by clinician opinion, and patient self-report. Cox proportional hazards modeling, Kaplan-Meier survival analysis, and regression modeling were employed. RESULTS: Median time to discontinuation for any reason was 70 days (95% confidence interval: 47; 95). Reasons for discontinuation were inadequate response in 64.1%, nonadherence in 6.2%, and adverse events in 4.1%; 25.6% who discontinued experienced an adequate response to treatment. In those patients who had an adequate response, age and country were significantly associated with time to medication discontinuation. Patient-reported nonadherence was 57.5% and clinician-reported nonadherence was 14.6% (62/426). At 3 months, nonadherent patients had significantly higher disease severity (CGI-S, P=0.0001; HAMD-17, P<0.0001), lower QoL ratings (EQ-5D tariff, P=0.0007; EQ-5D visual analog scale, P=0.0024), and lower response and remission rates (both P<0.0001) compared with adherent patients. The odds of response and remission were greater among adherent patients. CONCLUSION: Early discontinuation of antidepressants among Asian MDD patients was high. A total of 25.6% who discontinued prematurely were experiencing an adequate response to treatment. Nonadherent patients had significantly higher disease severity, lower QoL ratings, and lower response and remission rates compared with adherent patients.