Genetics of circadian rhythm disorders

Circadian rhythm sleep disorders are caused by an altered relationship between the circadian timing of sleep and the 24-hour world. Symptoms include insomnia, excessive sleepiness, and difficulty sleeping and/or waking at the desired time. Jet lag and shift work sleep disorder are circadian rhythm sleep disorders that occur when the environmental entrainment cues are rapidly changed in relation to an individual's circadian timing system. Other circadian rhythm disorders (advanced sleep phase [ASP] and delayed sleep phase [DSP]), are caused by fundamental alterations in the circadian timing of sleep relative to external time cues. Studies of ASP and DSP have led to the identification of several genetic variants, mainly in known circadian genes. Further studies are needed to identify genetic susceptibility to other circadian disorders. Better understanding of the physiologic and genetic basis of circadian rhythm disorders is crucial for the development of targeted therapies to improve sleep, performance, and health.