Aripiprazole (Abilify®) as an Adjunctive Treatment for Inadequate Response in Major Depressive Disorder

Inclusion Criteria: * Age : 18-65 * Patients with major depressive disorder according to DSM-IV criteria that have lasted \>8 weeks * MADRS total score of 18 or higher * Patients who responded inadequately (a score of \>18 on the MADRS) to first-line antidepressant treatment of 4 week duration * Current use of standard antidepressant treatment in monotherapy or combination of 2 antidepressants : escitalopram (10 - 20mg/d), fluoxetine(20 - 40mg/d), paroxetine CR(25 - 50mg/d), sertraline(100 - 150mg/d), mirtazapine (15 - 45mg/d), duloxetine (30 - 60mg/d) or venlafaxine ER(150-225mg/d) Exclusion Criteria: * Past history of hypersensitivity to aripiprazole * Primary diagnosis of MDD with psychotic feature, bipolar disorder, schizophrenia, schizoaffective disorder, other psychotic disorder or anxiety disorder, a history of alcohol/ drug abuse within the past 12 months, or a diagnosis of dementia * Clinically significant current Axis II (DSM-IV-TR) diagnosis * A significant risk of suicide corroborated by a score of ≥5 on item 10(suicidal thoughts) on the MADRS scale or by clinical judgment of the investigator * Pregnancy or in breast-feeding * Presence of a serious medical illness including cardiac, hepatic, renal, respiratory, endocrinologic, neurologic, or hematologic disease or physical disorder judged to significantly affect central nervous system function * Patients taking antipsychotics, mood stabilizer or any psychotropic medications besides antidepressants, except benzodiazepines or beta blockers or hypnotics * Patients with past treatment failures of aripiprazole