Circadian Rhythm Sleep Disorders and Phototherapy

Circadian rhythm sleep disorders are characterized by a desynchronization between the intrinsic circadian clock and the extrinsic light-dark cycle. As a result, symptoms of excessive sleepiness and insomnia can lead to significant impairment of daytime functioning. The six currently recognized circadian rhythm sleep disorders may involve either a primary abnormality of the patient's circadian clock or a normal functioning circadian clock with a newly changed external physical environment. Both light therapy and melatonin can be used strategically to realign the patient's endogenous sleep-wake cycle with the preferred sleep-wake schedule. Continued research of the underlying pathophysiology of circadian rhythm sleep disorders may lead to improved treatment strategies.