Diseases and Disorders

Parasomnias: Sleep Abnormalities

Alexander Skvortsov

 Sleep is an essential part of life. As described in our article on the necessity of sleep, sleep is extremely important to our physical, mental, and emotional wellbeing. However, sleep isn’t always the tranquil resting place that it should be. We are sometimes disturbed in our sleep by conditions known as parasomnias. Parasomnias, a word derived from the greek “para”, meaning as a part of, and “somnia”, or sleep, are abnormal behaviors that occur during sleep. However, unlike Sleep Apnea or Narcolepsy, Parasomnias are not necessarily related to sleep disorders, are common among the general population, and are usually not a cause for medical concern. Parasomnias are divided into 2 distinct categories: REM Parasomnias, which occur during the REM stage of sleep, and NREM Parasomnias, which occur during the non REM stages of sleep. REM Parasomnias are most prevalent among adult males above 50 years of age, while NREM Parasomnias are generally more common among children. Most Parasomnias are harmless, although some may cause sleepiness during the day, or create a health hazard. Treatment of Parasomnias is often unnecessary, as most have only a minimal effect on a person’s life. However, if episodes of the disorder are severe or abnormally frequent, consulting a sleep specialist is recommended (Markov, Jaffe, & Doghramji, 2006).


NREM Parasomnias

    There are several types of NREM parasomnias, which may have underlying genetic causes. These mainly affect children and infants. NREM parasomnias primarily concern arousal or problems with transitions between sleep stages.

    Confusional Arousals are episodes in which an individual abruptly awakens in a confused state—somewhat awake, yet with a foggy state of mind. Episodes of Confusional Arousal are often accompanied by rapid breathing, sweating, automatic behaviors, and a general sense of confusion (Markov, Jaffe, & Doghramji, 2006), and are generally much more common in infants and children. In these cases, it is recommended to let the episode run its course without interruption (Stores, 2001). Episodes of Confusional Arousal often follow being woken up.

    One of the most well-known parasomnias, sleepwalking, or somnambulism, affects mostly children, and decreases in prevalence after puberty; despite this, about 25% of children with somnambulism continue to suffer from it in adulthood. Somnambulism is, in basis, an arousal disorder in which the individual unconsciously performs various motor tasks, such as walking, speaking, or engaging in some sort of activity. These episodes generally last from several minutes to an hour, and are followed by complete amnesia regarding the event. Somnambulistic episodes have been associated with insufficient sleep, an irregular sleep schedule, stress, sickness, medications, and other arousal-related sleep disorders. Somnambulism is thought to be linked with epilepsy, as 47% of sleepwalkers experience abnormal EEG readings. Treatment is generally unnecessary unless the sleepwalking is frequent or results in harm to self or others (Kumar & Bharadwaj, 2007).

    Night terrors are occurrences of waking up with a feeling of fear or terror. These occur mostly in children from 3 to 7 of age. During an episode of sleep terrors, the individual usually sits up, screams, and appears frightened. The individual often exhibits an elevated pulse, dilated pupils, and intense sweating (Markov, Jaffe, & Doghramji, 2006). The individual may run around, and is often unresponsive at attempts to approach. Afterwards, amnesia generally sets in, with the individual usually only remembering difficulty breathing or a primal sense of terror (Stores, 2001).


REM Parasomnias

    These parasomnias occur during REM sleep, which is characterized by atonia (a type of paralysis).The brain is generally most active during the REM stage of sleep, so REM parasomnias are generally more visually intensive than NREM parasomnias. These include nightmares, hallucinations, and REM Sleep Behavior Disorder, which we explore in depth in our REM sleep behavior disorder article.

    Perhaps the most famous and common parasomnia is the nightmare. Not to be confused with night terrors, or the state of arousal while in a terrified state, nightmares are vivid, disturbing dreams that occur during the REM stage of sleep. Throughout the course of the nightmare, the dream becomes increasingly disturbing, terrifying, and threatening. Nightmares generally concern subjects of danger such as pursuit or imminent death. To be classified as a nightmare, the dream in question has to wake the sleeper. The individual almost never experiences the unconscious sleep movements or confusion. The amnesia experienced in most arousal NREM parasomnias is also absent in nightmares. Nightmares are often triggered by a traumatic event, or PTSD, in which case the nightmare will be centered around the event (Hasler & Germain, 2009).

    Alongside arousal-related NREM parasomnias and REM parasomnias, there are also several parasomnias not necessarily associated with a sleep stage. These include sleep paralysis, or episodes during which an individual is unable to move their limbs while waking up or falling asleep; sexsomnias, or sexual acts while sleeping; bruxism, or tooth grinding during sleep; and sleep eating, which is an occurrence during which an individual awakens and eats/drinks excessively. Most parasomnias are harmless, and can be safely ignored, however, if unsure, you should always consult a trained sleep specialist. 


  1. Hasler, B. P., & Germain, A. (2009). Correlates and treatments of nightmares in adults. Sleep Medicine Clinics, 4(4), 507–517. doi:10.1016/j.jsmc.2009.07.012

  2. Kumar, S., & Bharadwaj, R. (2007). Somnambulism: Diagnosis and treatment. Indian Journal of Psychiatry, 49(2), 123. doi:10.4103/0019-5545.33261

  3. Stores, G. (2001). Dramatic Parasomnias. Journal of the Royal Society of Medicine

  4. Markov, D., Jaffe, F., & Doghramji, K. (2006). Update on Parasomnias. Psychiatry Edgemont

Alexander Skvortsov

Alexander Skvortsov

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