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. Classification
The newest version of the International Classification of Sleep Disorders (ICSD, 3rd. Ed.) uses State Dissociation as the paradigm for parasomnias. Unlike before, where wakefulness, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep were considered exclusive states, research has shown that combinations of these states are possible and thus, may result in unusual unstable states that could eventually manifest as parasomnias or as altered levels of awareness.Although the previous definition is technically correct, it contains flaws. The consideration of the State Dissociation paradigm facilitates the understanding of the sleep disorder and provides a classification of 10 core categories. Non-rapid eye movement (NREM)-related parasomnias
NREM parasomnias are arousal disorders that occur during stage 3 (or 4 by the R&K standardization) of NREM sleep—also known as slow wave sleep (SWS). They are caused by a physiological activation in which the patients brain exits from SWS and is caught in between a sleeping and waking state. In particular, these disorders involve activation of the autonomic nervous system, motor system, or cognitive processes during sleep or sleep-wake transitions.Some NREM parasomnias (sleep-walking, night-terrors, and confusional arousal) are common during childhood but decrease in frequency with increasing age.
It can include such acts as masturbation, inappropriate fondling themselves or others, having sex with another person; and in more extreme cases, sexual assault. These behaviors are unconscious, occur frequently without dreaming, and bring along clinical, social, and legal implications. It has a lifetime prevalence of 7.1% and an annual prevalence of 2.7%. Sleepwalking (somnambulism)
Sleepwalking has a prevalence of 1–17% in childhood, with the most frequent occurrences around the age of eleven to twelve. About 4% of adults experience somnambulism. Normal sleep cycles include states varying from drowsiness all the way to deep sleep. Every time an individual sleeps, he or she goes through various sequences of non-REM and REM sleep. Anxiety and fatigue are often connected with sleepwalking. For adults, alcohol, sedatives, medications, medical conditions and mental disorders are all associated with sleepwalking. Sleep walking may involve sitting up and looking awake when the individual is actually asleep, and getting up and walking around, moving items or undressing themselves. They will also be confused when waking up or opening their eyes during sleep. Sleep walking can be associated with sleeptalking. Sleep terrors (night terrors/ pavor nocturnus)
Sleep terror is the most disruptive arousal disorder since it may involve loud screams and panic; in extreme cases, it may result in bodily harm or property damage by running about or hitting walls. All attempts to console the individual are futile and may prolong or intensify their confused state. Usually they experience amnesia after the event but it may not be complete amnesia.