N-3 Fatty Acids as the First-line Antidepressant Therapy: From Biomarkers to Clinical Subtypes

Inclusion Criteria: * the diagnostic criteria of DSM-IV for MDD * 18 to 65 years old * pre-study ratings of 18 or greater on the 21-item Hamilton Rating Scale for Depression (HAMD) * physically healthy under comprehensive evaluations in medical history, physical examination, and laboratory parameters tests * have not received any psychiatric treatment in 2 weeks * competent to receive a full explanation of this study and give written informed consent. Exclusion Criteria: * a recent or past history of other DSM-IV AxisI diagnoses besides unipolar major depression, including psychotic disorders, organic mental disorders, impulse control disorders, substance use disorder or substance abuse (last 6 months prior to the study), and bipolar disorders * AxisII diagnoses, including borderline and antisocial personality disorder * a notable medical comorbidity * acutely suicidal ideation and attempt were noted that close monitoring such as hospitalization is necessary * regular consumption of omega-3 PUFAs supplements or a habit of eating fish equal or more than 4 times per week