This experiment intends to explore the differences among various types of depression, as well as the differences between healthy subjects and depressed patients, and find possible biological markers from the severity of symptoms, social function and cognitive function of depressed patients, combined with EEG characteristics, biological test indicators (blood, faeces, hair, etc.) and functional magnetic resonance imaging data. To explore the changes in clinical symptoms, cognitive and social functions, and biological indicators of various types of patients before and after treatment, to provide references for the prognosis of various types, and to predict the future development of the disease according to the baseline indicators of patients; According to the above aspects, this experiment can follow up the patients with depression, track their disease development, and study the potential biological changes in the early stage of the disease, which has the potential to reveal the pathogenesis and provide guidance for the early diagnosis and intervention of depression.