Circadian Rhythm Sleep Disorders: Physiology of the Circadian Clock

Healthy sleep requires not only a sufficient quality and quantity of sleep but also sleep that occurs at the desirable time. The timing of sleep has long been known to be controlled by the interplay of circadian, homeostatic, and environmental factors. Newer findings (1) have pointed to mutations in the genes that control the human clock and to increased recognition of cultural practices as additional influences.