Movements or behaviors associated with sleep, sleep stages, or partial arousals from sleep that may impair sleep maintenance. parasomnias are generally divided into four groups: arousal disorders, sleep-wake transition disorders, parasomnias of rem sleep, and nonspecific parasomnias. (from thorpy, sleep disorders medicine, 1994, p191)

Parasomnias are a category of sleep disorders that involve abnormal movements, behaviors, emotions, perceptions, and dreams that occur while falling asleep, sleeping, between sleep stages, or during arousal from sleep. Parasomnias are dissociated sleep states which are partial arousals during the transitions between wakefulness, NREM sleep, and REM sleep, and their combinations..