As an important micro-ecological factor in human body, intestinal flora is closely related to the occurrence and development of major depressive disorder. The purpose of our study is to investigate a microbiome probe of depression. This study is a 6-months open trial that will enroll approximately 30 patients in major depressive disorders and 10 age- and sex-matched healthy controls. We will comparing gut bacteria community structures of pre- treatment, those of 1 month and 6 months after treatment to remission. With the microbiome change in a preliminary analysis of pre-and post-treatment, we will reveal the diversity before and after the depression treatment.

Participants (30 patients and 10 controls) will be recruited in the clinical psychological department of Beijing Chaoyang hospital. Patients with first-episode major depressive disorder confirmed by structured diagnostic interview (Chinese mini version) and assessment of symptom severity (Hamilton Depression Scale-17, HAMD-17) will be enrolled in a six-month open study. Healthy controls matched for age, sex and body-mass index (BMI) will have only baseline stool and electroencephalography (EEG) collections. We then will make an assessment of HAMD-17, patient-reported outcomes, and EEGs identified at the pre-treatment and those same parameters at the 1- to 6-month point. Treatment response (50% reduction in HAMD-17), treatment remission (HAMD-17<7, at least 3 weeks) will be analyzed with change in microbiome, inflammation markers and EEG.

We will analyze the differences in the intestinal flora community structure and diversity of patients and controls in order to obtain information on key different bacteria. We will conduct the correlation between each genus of bacteria in the intestinal flora and the total score of HAMD-17 in order to reveal the dynamic succession change of the intestinal flora with the disease state of major depressive disorder. The analysis with multiple testing corrections will be analyzed between depressive severity, EEG and gut microbiome composition.

The results of this study will provide the objective and direct biomarkers for major depressive disorder to achieve remission. This study will bring an important scientific basis to further optimizing treatment methods and improvie clinical effect.

Inclusion Criteria:

• The proportion between male and female in each of groups was 1:1
• Han Chinese
• Permanent resident population of Beijing
• Body Mass Index,18.5-23.9
• Signed informed consent

Exclusion Criteria:

• Other severe mental disease diagnosis
• Alcohol and other substance abuse or dependence
• Patients with contraindicated signs of duloxetine
• A history of clinically significant physical disorders, including any cardiovascular, liver, kidney, respiratory, blood, endocrine, and neurological disorders, as well as clinically significant laboratory abnormalities of unstable or expected therapeutic intervention during the study period
• The apparent risk of suicide and/or the patient is considered by the investigator to be at serious risk of suicide
• Patients who had received antibiotics, probiotics and hormones within one month

case : 30 patients of major depressive disorder Male or female participants ages 20-40 with Major Depressive Disorder, Intervention: Drug: duloxetine control：10 subjects without major depressive disorder