Patients with depression were enrolled and randomly divided into two groups, namely FMT combined with antidepressant group and Antidepressant alone group.The former received FMT capsules and antidepressants, and the latter received oral placebo and antidepressants for an 8-week intervention.Before and after intervention, venous blood samples were collected from patients for routine tests such as liver and kidney function to judge the safety of treatment. At the same time, psychological scales were used to evaluate the improvement of patients' depressive symptoms, so as to judge the efficacy and safety of FMT combined with antidepressants.

The main research content of this project is to observe the efficacy and safety of adjuvant FMT capsules in the treatment of depression by recruiting patients with first episode depression and randomly administering FMT combined with antidepressants or placebo combined with antidepressants.

In this study, patients with first episode depression were randomly divided into two groups. The first group was the experimental group, and FMT capsules (10^12 colony forming unit(CFU)/ capsule) were used in addition to conventional antidepressant therapy. The other group, a control group, was given placebo capsules with the same color, look and smell as the FMT capsules in addition to regular antidepressant therapy. Placebo capsules contain Lactobacillus probiotics for food use (10^12 CFU/ capsule). The changes of depressive symptoms and adverse reactions before and after treatment were observed in the two groups to explore the efficacy and safety of FMT capsule in the adjuvant treatment of depression.

The subjects (inpatients) were evaluated for meeting the eligibility requirements for this study according to the pre-specified inclusion and exclusion criteria, and demographic data (age, sex, marital status, educational level, employment, height and weight, smoking and drinking, and other general information as well as questionnaire assessment of eating habits) were collected. Improve laboratory examination (blood routine, liver function, kidney function and lipid), electrocardiogram and scale assessment.

Patients at the end of the screening period were randomly assigned to the experimental and control groups. Subjects will continue to receive FMT capsules or placebo capsules until the end of 8 weeks. During this period, both groups could use new selective serotonin reuptake inhibitors(SSRI)(fluoxetine, citalopram, escitalopram, Sertraline, paroxetine and fluvoxamine) recommended by current treatment guidelines, and the effective therapeutic dose of the drugs was added within 1 week. If, during the 8 weeks of the treatment period, the patient experienced significant fluctuations or severe adverse events that necessitates a change in antidepressant class, the study was terminated.

Benzodiazepines and medications that ameliorate side effects of antidepressants were allowed during the study period. Antipsychotics and mood stabilizers were prohibited. Electronic biofeedback therapy was allowed during the study, and transcranial magnetic stimulation and electroconvulsive non-convulsive therapy were prohibited.

Inclusion Criteria:

• Aged from 18 to 65 years
• Patients with first-episode depression who met the International Classification of Diseases(ICD)-10 diagnosis of depression
• Hamilton Depression Scale (HAMD) score ≥17
• Informed consent was obtained.

Exclusion Criteria:

• Use of antibiotics within 1 month
• Women are pregnant and lactating
• Patients with severe unstable cardiovascular disease, liver disease, kidney disease, etc
• Patients with malignant tumor or serious systemic disease
• Suffering from other mental disorders such as bipolar disorder, obsessive-compulsive disorder
• It is accompanied by intestinal diseases that seriously damage the intestinal barrier, such as inflammatory bowel disease, Crohn's disease, intestinal tuberculosis, ischemic bowel disease, and radiation enteritis