Inclusion Criteria:  meet the DSM-5 diagnostic criteria and their current episode show a 17-item Hamilton Rating Scale for Depression (HRSD-17) score of at least 18 show no clinical response to an adequate dose of an antidepressant could not tolerate at least two antidepressants in the current episode will be enrolled consecutively by trained psychiatrists Patients should receive a stable antidepressant regimen for at least 4 weeks before screening and continue during treatment  Exclusion Criteria:  had DSM-5 diagnosis for substance abuse within the past three months had taken monoamine oxidase inhibitors had an organic mental disorder, mental retardation, dementia, or other diagnosed neurological illness had a surgical condition or a major physical illness underwent course of electroconvulsive therapy (ECT) within the last three months the presence of a cardiac pacemaker, intracranial implant, or metal in the cranium taking any anticonvulsant or if more than three adequate antidepressant trials had failed (determined by antidepressant treatment history form).