insomnia

insomnia

n. difficulty in initiating or maintaining a restorative sleep, which results in fatigue, the severity or persistence of which causes clinically significant distress or impairment in functioning. Such sleeplessness may be caused by a transient or chronic physical condition or psychological disturbance. Also called agrypnia; ahypnia; ahypnosia; anhypnia. See disorders of initiating and maintaining sleep; fatal familial insomnia; initial insomnia; intermittent insomnia; middle insomnia; primary insomnia; pseudoinsomnia; terminal insomnia. —insomniac n.