Circadian rhythm sleep-wake disorders

**Definition:** Circadian rhythm sleep-wake disorders are disturbances of the sleep-wake cycle (typically manifest as insomnia, excessive sleepiness, or both) due to alterations of the circadian time-keeping system, its entrainment mechanisms, or a misalignment of the endogenous circadian rhythm and the external environment. Sleep logs and, if possible, actigraphy for a minimum of one week should be utilized to define the specific sleep-wake schedule disturbance.