IV. Circadian Rhythm Sleep Disorders
Circadian rhythm sleep disorders originate or develop from a misalignment between the person's sleep pattern and that which is desired or regarded as normal by society. Both intrinsic and extrinsic factors may be involved in circadian rhythm sleep disorders. Conditions such as jet lag, shift work disorders, and delayed or advanced sleep phase syndromes are examples of circadian rhythm sleep disorders. Patients with delayed sleep phase syndrome are often described as night owls—they are most comfortable going to sleep and waking much later than is socially acceptable. They may have insomnia if they go to bed at 11:00 p.m., for example, but fall asleep easily at 3:00 a.m. There is a genetic component to this disorder. A smaller number of patients have advanced sleep phase syndrome, resulting in early evening sleepiness and early morning awakening, which also has a genetic component.