The blues and rhythm.

Most organisms, including humans, show daily rhythms in many aspects of physiology and behavior, and abnormalities in the rhythms are potential risk factors for various diseases. Mood disorders such as depression are no exception. Accumulating evidence suggests strong associations between circadian disturbances and the development of depression. Numerous studies have shown that interventions to circadian rhythms trigger depression-like phenotypes in human cases and animal models. Conversely, mood changes can affect circadian rhythms as symptoms of depression. Our preliminary data suggest that the phosphorylation signal pathway of the clock protein may act as a common pathway for mood and clock regulation. We hypothesize that mood regulation and circadian rhythms may influence each other and may share a common regulatory mechanism. This review provides an overview of circadian disturbances in animal models and human patients with depression.