Circadian rhythm sleep-wake disorders are recurrent and chronic patterns of sleep and wake that arise when a substantial misalignment exists between internal rhythm and the required external timing of 24 hours. They can be classified into endogenous (delayed sleep-wake phase disorder, advanced sleep-wake phase disorder, irregular sleep-wake rhythm disorder, non 24 hour sleep-wake rhythm disorder), and exogenous (jet lag disorder, shift work disorder). They are caused by genetic factors, alterations of the circadian system, or its entrainment mechanisms, and social and working factors. Their diagnoses are based on the information of sleep logs, and actigraphy studies. The mainstay of treatment is chronotherapy, bright light exposure, and melatonin, although there is low evidence supporting the use of melatonin.
Beyond their impact on sleep and alertness, the disruption of the sleep-wake cycle has been implicated in the etiology of multiple diseases, such as cancer, cardiovascular disease, and affective-cognitive disorders.