The purpose of this study is to identify evidence-based guidelines for treating major depressive disorder to full remission in Taiwanese major depressive disorder (MDD) patients. To achieve this goal, the investigators aim to: (1) evaluate the risks and benefits of adjunctive pharmacotherapies for cognitive and metabolic consequences in MDD, and (2) clarify the shared biological mechanisms between mood, immune and metabolism homeostasis

The prevalence of insulin resistance did not significantly differ among the healthy controls and drug-naïve MDD patients before and after antidepressant treatment. Meanwhile, the current study indicated that antidepressants might affect insulin secretion independently of the therapeutic effects on MDD. Therapeutic strategies considering both treatment effectiveness and glucose-insulin homeostasis in MDD patients are necessary.

Inclusion Criteria:

• Age: 16-65 years old
• Signed informed consent by patient or legal representative
• Hamilton Rating Scale for Depression (HDRS) scores ≥ 16
• A diagnosis of MDD according to DSM-IV criteria made by a specialist in psychiatry

Exclusion Criteria:

• Monoamine oxidase inhibitor or antidepressant treatment prior to entering the study
• A DSM-IV diagnosis of substance abuse within the past three months
• An organic mental disease, mental retardation or dementia
• A serious surgical condition or physical illness
• Patients who were pregnant or breastfeeding