Disruption of Circadian Rhythms: A Crucial Factor in the Etiology of Depression

Figure 4

Schematic representation of a state of internal desynchronization. The biological clock (SCN) is synchronized with the dark-light cycle (external synchronization), and, in turn, the SCN synchronizes peripheral oscillators (internal synchronization). However, some oscillators may lose their synchronization with the SCN (dotted lines) due to alterations in the rhythmic output from the clock to the rest of the body or due to the interference given by nonphotic entraining stimuli, especially disturbed activity and feeding schedules. This uncoupling between the central clock and the peripheral oscillators is known as internal desynchronization, which results in physiological responses at the wrong time according to external requirements, which then leads to disease.