Developing circadian rhythmicity. Basic and clinical aspects

Abstract

Increasing evidence indicates that the circadian timing system is a fundamental hemostatic system that potently influences human behavior and physiology throughout development. Circadian clock function begins during fetal life, and photic regulation of circadian phase is present at birth in primates. After birth, there is progressive maturation of the circadian system, with day-night rhythms in activity and hormone secretion developing between 1 and 3 months of age. Several disorders of the circadian system are now recognized and include clock disorders and problems related to inadequate entrainment of circadian phase. Treatments for several circadian system disorders are now available and include light therapy and melatonin. With the continued elucidation of circadian system development and influences on human physiology and illness, it is anticipated that consideration of circadian biology will become an increasingly important component of clinical care.