Patients with major depressive disorder will receive 20 mg/day of fluoxetine for six weeks. Symptom severity was assessed by the 17-item Hamilton Depression Rating Scale (HAMD-17) at weeks 0, 1, 2, 3, 4 and 6. Stable response is defined as a reduction of 50% or more of the HAMD-17 score at week 4 and week 6 of treatment. Receiver operating characteristic curve will be used to determine the cutoff point of the percentage of HAMD-17 score reduction between stable responders and nonresponders at weeks 1, 2, 3 and 4.
