Parasomnia

Overview
A parasomnia is any sleep disorder such as sleepwalking, sleepeating, sleep sex, teeth grinding, night terrors, rhythmic movement disorder, REM behaviour disorder, restless legs syndrome, and somniloquy, characterized by partial arousals during sleep or during transitions between wakefulness and sleep. Parasomnias are often associated with stress and depression, and biological factors may also be involved. Many parasomnias are more common in children than in adults.

Unlike dyssomnias, parasomnias do not involve abnormalities of the mechanisms generating sleep-wake states, nor of the timing of sleep and wakefulness. Rather, parasomnias represent the activation of physiological systems at inappropriate times during the sleep-wake cycle. In particular, these disorders involve activation of the autonomic nervous system, motor system, or cognitive processes during sleep or sleep-wake transitions.

Parasomnias occur during deep sleep (stages III and IV). On an electroencephalogram (EEG), this corresponds to slow wave sleep.

Many parasomnias, such as sleepwalking, have serious risks. For example, a person with REM behavior disorder, while trying to swing a tennis racket in a dream, can potentially injure their bedmate. People with night terrors can prevent others from sleeping well, as well as waking themselves up. For these reasons, parasomniacs sometimes need medical treatment.