Insomnia and circadian rhythm sleep disorders

The circadian system regulates the timing of physiological and behavioral processes, as well as the propensity for sleep and alertness. Alterations in the circadian clock or misalignment between the timing of the internal circadian clock and the external physical or social environment result in insomnia during the night and sleepiness during the day. Because treatment of CRSD requires behavioral and pharmacologic approaches aimed to improve circadian function and the synchronization of circadian rhythms, it is essential to differentiate these patients from those with primary insomnia or hypersomnia. Furthermore, CRSDs are often seen in association with comorbid psychiatric disorders and other sleep disorders. During the past decade, there have been tremendous advances in our understanding of the neurobiology of circadian rhythm and sleep regulation. These recent advances should lead to improved diagnostic and treatment approaches for CRSDs.