Table 1 The inclusion and exclusion criteria for MDD patients and healthy controls, respectively

1200-MDD patients

(1) age between 18 and 55 years at the time of enrollment;

(2) diagnosis of MDD based on the Chinese Version of MINI according to DSM-IV TR;

(3) first-episode or relapsed;

(4) having the ability of reading and writing to complete the questionnaire and psychological assessment;

(5) providing written confirmation of informed consent.

(1) lifetime or current diagnosis of other psychotic disorder, alcohol/substances dependence or cognitive impairment;

(2) severe somatic diseases, such as severe cardio-cerebral vascular diseases, respiratory diseases, liver diseases, kidney diseases, or malignant tumors;

(3) not signed the informed consent;

(4) been engaging in other studies.

600-MDD patients subgroup

Besides those same as 1200-MDD patients’, more inclusion criteria are as the follows:

(1) first-episode or relapsed more than1 time in the past 3 years and in acute episode period;

(2) total score of HRSD₁₇ ≥ 14 when being screened;

(3) not taking anti-depressant regularly in the past 2 weeks or should change anti-depressant according to the psychiatrist’s advice.

Besides those same as 1200-MDD patients’, more exclusion criteria are as the follows:

(1) resistant depression (not improved after taking 2 kinds of anti-depressant with adequate dosage and duration;

(2) having history of epilepsy;

(3) taking MECT therapy in the past 3 months;

(4) pregnant or breast-feeding.

1200-Healthy controls

(1) age between 18 and 55 years at the time of enrollment;

(2) providing written confirmation of informed consent prior to engaging the study.

(1) lifetime or current diagnosis of any mental diseases;

(2) severe somatic diseases, such as severe cardio-cerebral vascular diseases, respiratory diseases, liver diseases, kidney diseases, or malignant tumors;

(3) not signed the informed consent;

(4) been engaging other studies.