Sleep Disorders [Disease/Finding] Dyssomnias [Disease/Finding] N0000004220 44186003 C8618 D020920 Dyssomnias 1022841 A broad category of sleep disorders characterized by either hypersomnolence or insomnia. The three major subcategories include intrinsic (i.e., arising from within the body) (SLEEP DISORDERS, INTRINSIC), extrinsic (secondary to environmental conditions or various pathologic conditions), and disturbances of circadian rhythm. (From Thorpy, Sleep Disorders Medicine, 1994, p187) C0700201 M0328379 Dyssomnias