Lexapro®'s Efficacy After Dose Escalation in Remission Study

Inclusion Criteria: * Age: 18 \~ 65 * Patient with major depressive disorder according to DSM-IV criteria * Patient have signed on the informed consent, and well understood the objective and procedure of this study. * MADRS total score ≥ 18 * Competent patient who is manage to answer the questionnaires. * In case of female at child-bearing age, consent to use appropriate contraceptive methods(oral pill, contraceptive injection, intrauterine device, double barrier method and contraceptive patch) during entire duration of this study. Exclusion Criteria: * In previous depressive episodes, no efficacy although more than one antidepressant treatment * Allergy or hypersensitivity to escitalopram * Diagnosed to schizophrenia or bipolar disorder or schizoaffective disorder (DSM-IV) * MADRS 10 score ≥ 5, or patient who is supposed to be impossible to participate to this study due to clinical risk of suicide or aggressive behavior based on clinician's opinion * Pregnant or breast-feeding female patient * Significant biochemical or hematological abnormality or abnormal finding of urinalysis, based on clinician's opinion * Significant severe medical condition * Patients who take antipsychotics or mood stabilizer or other psychiatric drugs excluding benzodiazepines or beta blockers or hypnotics * History of participating to other investigational drug trial within 1month prior to screening * Investigator or employee at clinical trial center, personnel related to investigator or trial center on this or other study, or family of employee or investigator