Learning Objectives

  • Explain NREM sleep arousal disorders (sleepwalking and night terrors)
  • Explain REM sleep behavior disorder (RBD)


A parasomnia is one of a group of sleep disorders in which unwanted, disruptive motor activity and/or experiences during sleep play a role. Parasomnias can occur in either REM or NREM phases of sleep. Parasomnias include NREM sleep arousal disorders of sleepwalking and sleep terrors, nightmare disorder, REM sleep behavior disorder, and restless leg syndrome.

Link to Learning

Listen to the following clip from NPR’s “This American Life” episode “Fear of Sleep” to hear about some experiences of people with parasomnia sleep disorders and how it has affected their lives. Listen specifically to the 1:40–6:25 timeframe.

NREM Sleep Arousal Disorders


A person wearing pajamas standing in a mall with a pillow under their arm.

Figure 1. Sleepwalking and night terrors take place during non-REM sleep.

In sleepwalking or somnambulism, the sleeper engages in relatively complex behaviors ranging from wandering about to driving an automobile. During periods of sleepwalking, sleepers often have their eyes open, but they are not responsive to attempts to communicate with them. Sleepwalking most often occurs during slow-wave sleep, but it can occur at any time during a sleep period in some affected individuals (Mahowald & Schenck, 2000).

Historically, somnambulism has been treated with a variety of pharmacotherapies ranging from benzodiazepines to antidepressants. However, the success rate of such treatments is questionable. Guilleminault et al. (2005) found that sleepwalking was not alleviated with the use of benzodiazepines. However, all their somnambulistic patients who also suffered from sleep-related breathing problems showed a marked decrease in sleepwalking when their breathing problems were effectively treated.

Night Terrors

Night terrors result in a sense of panic in the sufferer and are often accompanied by screams and attempts to escape from the immediate environment (Mahowald & Schenck, 2000). Although individuals suffering from night terrors appear to be awake, they generally have no memories of the events that occurred and attempts to console them are ineffective. Typically, individuals suffering from night terrors will fall back asleep again within a short time. Night terrors apparently occur during the NREM phase of sleep (Provini, Tinuper, Bisulli, & Lagaresi, 2011). Generally, treatment for night terrors is unnecessary unless there is some underlying medical or psychological condition that is contributing to the night terrors (Mayo Clinic, n.d.).

Nightmare Disorder

A boy is sleeping and a dark shadowy figure appears behind his bed.

Figure 2. Nightmares occur during REM sleep.

Nightmare disorder is a sleep disorder characterized by frequent nightmares. The nightmares, which often portray the individual in a situation that jeopardizes their life or personal safety, usually occur during the REM stages of sleep (unlike night terrors, which occur during NREM sleep and do not follow a storyline in the way that nightmares do). Though most people have experienced at least one nightmare during their life, subjects with nightmare disorder experience them with a greater frequency.

Nightmares also have to be distinguished from bad dreams, which are less emotionally intense. Furthermore, nightmares contain more stories of aggression than bad dreams and more unhappy endings. Finally, people experiencing nightmares feel more fear than for bad dreams.


Studies have reported that nightmare disorders were present in 50–70% of the cases for PTSD, in 17.5% for depression, in 18.3% for insomnia, in 16.7% for schizophrenia, and in 49% for borderline personality disorder.[1] For all psychiatric disorders taken together, nightmare disorders are present in 29.9% of the cases, a much bigger rate than for the general population, which is 2%-5%. Nightmare disorders can also be associated with sleep disorders such as night terrors, chronic insomnia, and sleep-disordered breathing. The presence of nightmares before a trauma would influence the severity of PTSD symptoms. Furthermore, having nightmares is linked to a significantly higher risk of attempting suicide and of death by suicide.

Nightmares also seem to be correlated with some personality factors. Studies found an association between anxiety, depression, and nightmares in insomnia, while only a small relationship was found in other populations. Neuroticism would be also link to nightmares.  Nevertheless, people with a higher score of neuroticism could be better at recalling their nightmares during the self-report assessment, which could have an influence on this association.

Key Takeaways: NREM Sleep Arousal Disorders

REM Sleep Behavior Disorder (RBD)

REM sleep behavior disorder (RBD) occurs when the muscle paralysis associated with the REM sleep phase does not occur. Individuals who suffer from RBD have high levels of physical activity during REM sleep, especially during disturbing dreams. These behaviors vary widely, but they can include kicking, punching, scratching, yelling, and behaving like an animal that has been frightened or attacked.

A pair of feet wearing white ankle socks in bed.

Figure 3. Restless leg syndrome commonly kicks in during the evening hours or during sleep, frustrating a person’s ability to relax or get a good night’s sleep.

The prevalence of REM sleep behavior disorder (RBD) is approximately 0.5%-1% in the general population and 2% in older adults. A large number of people are undiagnosed. The male to female diagnosis ratio is as high as 9:1. People with REM sleep behavior disorder (RBD) often have a comorbidity with mental health illness like a mood disorder and take anti-depressants or a history of traumatic brain injury.[2] This disorder is associated with a number of neurodegenerative diseases such as Parkinson’s disease. In fact, this relationship is so robust that some view the presence of RBD as a potential aid in the diagnosis and treatment of a number of neurodegenerative diseases (Ferini-Strambi, 2011).

Clonazepam, an anti-anxiety medication with sedative properties, is most often used to treat RBD. It is administered alone or in conjunction with doses of melatonin (the hormone secreted by the pineal gland). As part of treatment, the sleeping environment is often modified to make it a safer place for those suffering from RBD (Zangini, Calandra-Buonaura, Grimaldi, & Cortelli, 2011).

Restless Leg Syndrome

A person with restless leg syndrome has uncomfortable sensations in the legs during periods of inactivity or when trying to fall asleep. This discomfort is relieved by deliberately moving the legs, which, not surprisingly, contributes to difficulty in falling or staying asleep. Restless leg syndrome is quite common and has been associated with a number of other medical diagnoses, such as chronic kidney disease and diabetes (Mahowald & Schenck, 2000). There are a variety of drugs that treat restless leg syndrome: benzodiazepines, opiates, and anticonvulsants.

Watch It

Watch this video to learn more about the risk factors, symptoms, and treatment options for those with RBD.

You can view the transcript for “REM Sleep behavior disorder” here (opens in new window).

Try It

Dig Deeper: A Sleepwalking Defense?

On January 16, 1997, Scott Falater sat down to dinner with his wife and children and told them about the difficulties he was experiencing on a project at work. After dinner, he prepared some materials to use in leading a church youth group the following morning, and then he attempted to repair the family’s swimming pool pump before retiring to bed. The following morning, he awoke to barking dogs and unfamiliar voices from downstairs. As he went to investigate what was going on, he was met by a group of police officers who arrested him for the murder of his wife (Cartwright, 2004; CNN, 1999).

Yarmila Falater’s body was found in the family’s pool with 44 stab wounds. A neighbor called the police after witnessing Falater standing over his wife’s body before dragging her into the pool. Upon a search of the premises, police found blood-stained clothes and a bloody knife in the trunk of Falater’s car, and he had blood stains on his neck.

Remarkably, Falater insisted that he had no recollection of hurting his wife in any way. His children and his wife’s parents all agreed that Falater had an excellent relationship with his wife and they couldn’t think of a reason that would provide any sort of motive to murder her (Cartwright, 2004).

Scott Falater had a history of regular episodes of sleepwalking as a child, and he had even behaved violently toward his sister once when she tried to prevent him from leaving their home in his pajamas during a sleepwalking episode. He suffered from no apparent anatomical brain anomalies or psychological disorders. It appeared that Scott Falater had killed his wife in his sleep, or at least, that is the defense he used when he was tried for his wife’s murder (Cartwright, 2004; CNN, 1999). In Falater’s case, a jury found him guilty of first degree murder in June of 1999 (CNN, 1999); however, there are other murder cases where the sleepwalking defense has been used successfully. As scary as it sounds, many sleep researchers believe that homicidal sleepwalking is possible in individuals suffering from the types of sleep disorders described below (Broughton et al., 1994; Cartwright, 2004; Mahowald, Schenck, & Cramer Bornemann, 2005; Pressman, 2007).

Try It


parasomnia: a group of sleep disorders where unwanted, disruptive motor activity, or other experiences during sleep play a role in their life

nightmare disorder: the sleep disorder that is characterized by frequent nightmares

night terrors: when a person experiences a sense of panic that is often accompanied by screams and attempts to escape from the immediate environment

REM sleep behavior disorder (RBD): when the muscle paralysis associated with the REM sleep phase does not occur

restless leg syndrome: the sleep disorder where a person has uncomfortable sensations in the legs during periods of inactivity or when trying to fall asleep.-

  1. Swart, Marijke L.; van Schagen, Annette M.; Lancee, Jaap; van den Bout, Jan (2013). "Prevalence of Nightmare Disorder in Psychiatric Outpatients". Psychotherapy and Psychosomatics. 82 (4): 267–268. doi:10.1159/000343590. ISSN 1423-0348. PMID 23735876.
  2. UpToDate.