Clinical Study on the Safety and Effectiveness of Vagus Nerve Stimulation in the Treatment of Refractory Depression

Inclusion Criteria: 1. patients with treatment-resistant depression (patients with Hamilton depression scale (HAMD) score reduction rate still less than 50% after adequate treatment with two or more antidepressants) 2. age 18-65; Male or female 3. the patient has a depressive course of 2 years or more or has 2 or more major depressive episodes 4. HAMD-17 score\> 17 was at baseline Exclusion Criteria: 1. pregnant or lactating women, women of childbearing age who plan or have no safe contraceptive measures 2. a patient who is or has been diagnosed with a mental disorder other than depression; Depressive episode with psychotic symptoms 3. patients currently at serious risk of suicide 4. prior 12 months of alcohol or substance dependence, or prior 6 months of substance abuse other than nicotine 5. patients with cardiovascular diseases (myocardial infarction or cardiac arrest) and organic brain diseases (such as cerebral hemorrhage, massive cerebral infarction, encephalitis and epilepsy) 6. accept other clinical trials 7. patients requiring systemic mri after implantation