about 150 depression patients were divided into three subgroups, for each group was treated by one antidepressant eg.escitalopram,duloxetine,bupropion.Brain magnetic resonance imaging data were conducted for all patients at baseline, 1 days, 14 days and 12 weeks after treatment. The blood concentration detection, symptom change, cognitive function tests were also conducted. combined with these results the investigators aim to determine the different mechanisms of drug efficacy of antidepressants with different mechanisms and to explore different mechanisms of brain function for effective or ineffective drug response
