When sleep won't come.
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D002648:Child; D006801:Humans; D007231:Infant, Newborn; D009730:Nursing Assessment; D009736:Nursing Process; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology; D012893:Sleep Wake Disorders / Q000175:diagnosis / Q000503:physiopathology*