This study aims at investigating the special effectiveness of antidepressant effect of
Fluvoxamine for endogenous depression. The investigators also aim to assess the effect of
Fluvoxamine on the multimodal magnetic resonance imaging(MRI), blood cytokines, feces
bacteria flora and neuropsychological performance in depression patients with melancholic
features. The investigators further aim to identify the predictors of Fluvoxamine's
antidepressant effeect using the above techniques.