OBJECTIVE: This article aims to identify baseline sociodemographic and clinical characteristics associated with the duration of the index major depressive episode (MDE) and to assess the effect of the current MDE duration on response and remission rates with up to 14 weeks of citalopram. METHOD: Eligible participants met DSM-IV criteria for nonpsychotic major depressive disorder, scored >or= 14 on the 17-item Hamilton Rating Scale for Depression (HAM-D-17), and were not resistant to adequate antidepressant treatment in the current episode. The first patient was enrolled in July 2001 and the last visit for the last patient in follow-up was in March 2006. The evaluable sample (N = 2851) was divided into 4 groups based on the index MDE duration at study entry: acute (or= 42 months, N = 394). These 4 groups were compared in terms of baseline sociodemographic and clinical characteristics and treatment outcomes. Citalopram was generally begun at 20 mg/day and raised to 40 mg/day by weeks 2 through 4 and to 60 mg/day (final dose) by weeks 4 through 6. Logistic regression models with adjusted post hoc analyses were used to control for associated baseline characteristics. Response was defined as >or= 50% reduction in baseline 16-item Quick Inventory of Depressive Symptomatology-Self-Report (QIDS-SR-16) scores at exit. Remission was defined as