Parasomnia: A sleep disorder in which odd or dangerous events occur that intrude on sleep. The parasomnias include sleep talking, sleepwalking (somnambulism), sleep terrors, REM behavior disorder, and nocturnal dissociative disorder.
Sleep talking may range from a word or two to an entire speech of which the sleep talker has no recollection; it is harmless. Sleepwalking involves nocturnal trips, tends to occur in children and can run in families. Sleep terrors are like severe nightmares but with intense fear often accompanied by screaming and fighting. Fifteen per cent of children experience night terrors after general anesthesia, occurring anywhere up to 2 weeks after surgery. They appear to be awake but are actually in a deep sleep and will not respond to shaking or being talked to. REM behavior disorder involves acting out dreams during rapid eye movement (REM) sleep; it is most common in older men (who usually can recall the dreams) and treatment is with an antidepressant or tranquillizer. Nocturnal dissociative disorder is a condition in which people leave bed and re-enact episodes of sexual or physical abuse.