Abstract: As a worldwide public health challenge, depression negatively affects personal health and substantially increases the public burden of medical care. Prior research found a strong association between disrupted circadian rhythm and depression, suggesting the important role of chronotype in depression research. Individuals can be categorized into three general chronotypes: evening types (E-Types), morning types (M-Types), and neither type (N-Types). Most of studies show that evening types are independently associated with severe depressive symptoms, while morning types are a protective factor against depression. Behavioral mechanisms (such as emotion regulation) and neural mechanisms of amygdala and cingulate cortext may help us understand the effects of chronotype on depression. Future research should explore the sub-dimensions of chronotype, apply the prospective cohort design, and assess the proposed psychological and physiological mechanisms. In addition, the study has important implications to develop effective interventions to reduce depression.

Key words: depression, chronotype, emotion regulation