Insomnia in circadian dysrhythmias.

Insomnia is one of the most common symptoms of disordered sleep. The etiology of insomnia is multifaceted, and the correct diagnosis will lead to effective treatment. One cause of insomnia that is often overlooked results from a conflict in schedules and desynchronization between the intrinsic sleep-wake propensity of a person and his or her 24-hour physical and social environment. Sleep propensity is governed by the complex interactions of an oscillating circadian rhythm and a monotonous homeostatic process. This review describes the basic physiology of the circadian system and, based on these understandings, discusses the various clinical manifestations of and treatments for circadian rhythm sleep disorders.