This is a prospective clinical cohort study of depression. The study was intended to include 300 patients with depression and 100 healthy controls. The study consisted of two phases: the baseline period and the follow-up period, in which all subjects were comprehensively collected, and the follow-up period in which all subjects were followed up at least once a year and data were collected. For patients with major depressive disorder, the follow-up methods included fixed visit and planned visit, and the follow-up time point covered the whole course of depressive disease(baseline, 2nd weekend±7days, 6th weekend±14days, 8th weekend±14days, 12th weekend±14days, Week 14-104 Every 4 weekends ± 14 days). Based on standardized, multi-strategy follow-up system and mobile health technology, long-term follow-up of patients with major depressive disorder was realized, and key nodes of patients' disease fluctuations were captured in time. High quality multidimensional data were collected, including demographic, clinical, EEG and eye movement data. Finally, the objective index system of depression was constructed, and the diagnosis, efficacy/recurrence prediction and suicide warning models of depression were established.

1. Research Treatment

   1.1 Drug treatment

   The patient did not take antidepressant treatment at least 14 days before enrollment (the patients treated with fluoxetine before enrollment should stop using it for at least 28 days). During 8 weeks, all subjects with major depressive disorder received effective dosages of selective serotonin reuptake inhibitors, and all subjects with major depressive disorder were limited to a single class of antidepressants. If the antidepressant treatment plan needed to be adjusted, one antidepressant should be selected as far as possible, and combined treatment with two or more antidepressants should not be allowed. Antipsychotics and mood stabilizers are not permitted. If the treatment of selective serotonin reuptake inhibitors is not effective after eight weeks, the drugs can be considered for replacement. The drugs for replacement include but are not limited to selective serotonin reuptake inhibitors.

   1.2 Other treatment Settings

   Psychotherapy and TMS are allowed. The method, frequency, and duration of therapy should be recorded.

   1.3 Treatment compliance

   Participants were reminded to follow the medication regimen and their medication use was recorded at each visit. Non-use of prescription drugs for ≥70% of the time is considered noncompliance, and the reason for noncompliance should be checked. If there was a protocol violation, the protocol violation was recorded and the follow-up was continued as scheduled.

2. Observation index

Main observation indicators:

Clinical effect: Changes of clinical symptoms in acute phase, maintenance phase and long-term follow-up period. Changes in HAMD-17 scores at different follow-up points compared with baseline were used as the main efficacy evaluation index in this study. The evaluation criteria of clinical efficacy and significant endpoints at different stages are as follows:

① Early onset: The total score of HAMD-17 decreased by more than 20% from baseline after 2 weeks of treatment;

② Effective: The total score of HAMD-17 was reduced by more than 50% compared with baseline; Stable and effective was defined as two consecutive HAMD-17 scores decreased by more than 50% from baseline at the 8th weekend of the acute phase.

2.1 A method of measuring or evaluating observational indicators

1) General demographic data survey The patient's date of birth, gender, height, weight, nationality, marital status, occupation type and years of education were investigated.

Clinical information collection

2）Medical history information:

• Time of first onset of major depressive disorder/bipolar disorder
• The onset of the current depressive episode
• Total episodes (including this one) : depressive episodes

2.2 Scale evaluation(baseline, 2nd weekend±7days, 6th weekend±14days, 8th weekend±14days, 12th weekend±14days, Week 14-104 Every 4 weekends ± 14 days)：

We collect scale data of patients with major depressive disorder at different point (baseline, 2nd weekend±7days, 6th weekend±14days, 8th weekend±14days, 12th weekend±14days, Week 14-104 Every 4 weekends ± 14 days), and collect scale data of healthy controls during the baseline period.

self-rating scale： Snaith-Hamilton Pleasure Scale, SHAPS Generalized Anxiety Disorder,GAD-7 Patient Health Questionnare, PHQ-9 Hypomania Check List,HCL-33 Sheehan Disability Scale，SDS Childhood Trauma Questionnaire，CTQ Big 5 Personality Questionnaire， B5PQ Dysfunctional Attitude Scale，DAS Interpersonal Reactivity Index-C Scale for Suicide Ideation，SSI

Other rating scale Hamilton Depression Rating Scale for Depression - 17-item，HAMD-17 Hamilton Anxiety Scale，HAMA Brief Psychiatric Rating Scale, BPRS 4 items

2.3 EEG and eye movement data collection (baseline, 2nd weekend±7days, 6th weekend±14days, 8th weekend±14days, 12th weekend±14days, Week 14-104 Every 4 weekends ± 14 days)

We collect EEG and eye movement data of patients with major depressive disorder at different point(baseline, 2nd weekend±7days, 6th weekend±14days, 8th weekend±14days, 12th weekend±14days, Week 14-104 Every 4 weekends ± 14 days), and collect EEG and eye movement data of healthy controls during the baseline period.

Inclusion Criteria:

• Out-patient or in-patient aged 18-65 years (including 18 and 65 years), regardless of gender;
• The Chinese version of the Concise International Neuropsychiatric Interview (M.I.N.I.) 7.0.2 type interview, in line with the DSM-5 Diagnostic criteria for major depressive disorder, either first or recurrent;
• Screening and baseline Hamilton Depression Scale (HAMD-17) Score ≥14;
• No antidepressants were taken for at least 14 days prior to enrollment (patients treated with fluoxetine prior to enrollment should Stop for at least 28 days);
• A single class of antidepressant medication is planned;
• Primary school education or above, able to understand the research content;
• Understand and voluntarily participate in this study, and I sign the informed consent.

Exclusion Criteria:

• A current or previous DSM-5 diagnosis of a major mental disorder other than major depressive disorder, Such as neurodevelopmental disorders, neurocognitive disorders, schizophrenia and other psychotic disorders, bipolar disorder Sensory disorder, obsessive disorder, panic disorder, post-traumatic stress disorder, alcohol (or drug) dependence or abuse User and personality disorder;
• depression secondary to an organic mental disorder caused by a systemic disease or a neurological disease Seizures, such as depression caused by hypothyroidism;
• Severe or unstable cardiovascular, respiratory, liver, kidney, endocrine, hematological or other conditions Other systemic diseases were not considered suitable for inclusion in this study.
• During the screening period or baseline period, the investigators considered that the physical examination and laboratory examination of the patients were abnormal and judged to have significant clinical significance Bedsense;
• had received systemic Modified Electric therapy (Modified Electric) 3 months before screening Convulsive Therapy, MECT) or Transcranial Magnetic stimulation (Transcranial Magnetic Stimulation (TMS), Deep Brain Stimulation (DBS), Vagus Nerve Stimulation (VNS);
• The withdrawal of psychotropic drugs did not reach 7 half-lives before screening.

Depression is a mental state characterized by persistent low mood, loss of interest and pleasure in daily activities, autonomic disorders and decreased energy, resulting in varying degrees of impairment of social and occupational functioning.