Tags: Disease.
Non-24-hour sleep–wake disorder (non-24) is one of several types of chronic circadian rhythm sleep disorders (CRSDs). It is defined as a complaint of insomnia or excessive sleepiness related to abnormal synchronization between the 24-hour light–dark cycle and the endogenous circadian rhythms of sleep and wake propensity. Symptoms result when the non-entrained (free-running) endogenous circadian rhythm drifts out of alignment with the desired or conventional sleep–wake schedule.