Parasomnia

A parasomnia is any unwanted behavior, experience or physical event that happens while falling asleep, during sleep or on waking, such as sleepwalking, sleep terrors or acting out dreams.

Sleep specialists divide parasomnias by the sleep stage they arise from. Non-REM parasomnias, including sleepwalking, sleep terrors and confusional arousals, occur during deep slow-wave sleep in the first third of the night, when the brain is partly awake and partly asleep; the person is confused, hard to wake and usually has no memory of the event. REM parasomnias include nightmare disorder, sleep paralysis and REM sleep behavior disorder, in which the normal muscle paralysis of REM sleep fails and the sleeper physically acts out dreams. Other parasomnias include sleep-related eating, bedwetting and exploding head syndrome.

Parasomnias are common in children and usually fade, but in adults they can be triggered by sleep deprivation, alcohol, fever, stress, sleep apnea and certain medications, and REM sleep behavior disorder in older adults can precede Parkinson's disease by years. Evaluation includes a detailed history from the sleeper and a bed partner, a sleep diary, and video polysomnography when injury or a REM disorder is suspected. Management centers on safety measures, regular sleep schedules and addressing triggers, with medication in selected cases. Cannabidiol has been reported in small case series for REM sleep behavior disorder, but the evidence is limited and no cannabinoid has an approved use for any parasomnia.