Merck Manual

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Richard J. Schwab

, MD, University of Pennsylvania, Division of Sleep Medicine

Reviewed/Revised May 2022 | Modified Sep 2022
Topic Resources

Parasomnias are unusual behaviors that occur just before falling asleep, during sleep, or when waking up.

Various unconscious and largely unremembered behaviors can occur during sleep in children and adults.

Just before falling asleep, almost all people occasionally experience brief, involuntary jerks of the arms or the entire body. Occasionally, the legs jerk. Some people also experience sleep paralysis (attempting but being unable to move) or brief fleeting images or thoughts when they are just falling asleep or awakening. People may clench or grind their teeth or have nightmares.

Sleepwalking, head-banging, and night terrors are more common among children and can be very distressing for their parents. Usually, children do not remember these episodes. Other parasomnias include nightmares, rapid eye movement (REM) sleep behavior disorder, and sleep-related leg cramps.

Night terrors

These frightening episodes result in sitting up, screaming, and flailing about. The eyes are wide open, and the heart races. People appear very frightened. Episodes usually occur when people are partially aroused or when they just awakened from the deepest stage of nonrapid eye movement (NREM) sleep, typically during the first few hours of the night.

Night terrors differ from nightmares and may lead to sleepwalking.

Night terrors are more common among children. Children should not be awakened because doing so makes them even more frightened. Although children appear highly distressed, they have no memory for the events or mental images after awakening and do not have psychologic problems as a result of these behaviors. Parents need not be overly distressed. Children usually stop having episodes when they become older.

Episodes in adults are often associated with psychologic problems or alcohol use disorder.

For children, reassurance from their parents may be all that is needed. If school work or other activities are affected, treating older children with certain benzodiazepines Misuse of Antianxiety Medications and Sedatives Antianxiety and sedative medications are prescription drugs used to relieve anxiety and/or help with sleep, but their use can result in dependency and a substance use disorder. Using prescription... read more (such as diazepam, clonazepam, or alprazolam) may help. These drugs, which are used to treat anxiety (antianxiety drugs Treatment ) and induce sleep (sedatives), are given 90 minutes before bedtime. They can help children sleep and make night terrors less likely to occur. However, long-term use of benzodiazepines can lead to drug dependence Misuse of Antianxiety Medications and Sedatives Antianxiety and sedative medications are prescription drugs used to relieve anxiety and/or help with sleep, but their use can result in dependency and a substance use disorder. Using prescription... read more . Thus, these drugs are usually taken for only a relatively short time (about 3 to 6 weeks).

Adults may benefit from psychotherapy or drug treatment.


Nightmares are vivid, frightening dreams, followed by sudden awakening. Children are more likely to have nightmares than adults. Nightmares occur during rapid eye movement (REM) sleep.

Nightmares are more likely to occur when people are under stress, have a fever, are excessively tired, or have consumed alcohol.

Treatment of nightmares, if necessary, focuses on any underlying problem.

Sleepwalking (somnambulism)

Sleepwalking, most common in late childhood and adolescence, is walking in a semiconscious manner without being consciously aware of it. It occurs during the deepest stage of NREM sleep.

Sleepwalkers may mumble repetitiously and can hurt themselves by walking into obstacles. Most sleepwalkers have no memory of sleepwalking.

Not getting enough sleep and behaving in ways that are not conducive to sleep (see table Changes in Behavior to Improve Sleep Changes in Behavior to Improve Sleep Changes in Behavior to Improve Sleep ) can make sleepwalking more likely. For example, consuming caffeine, exercising, or watching an exciting television show before bedtime may trigger sleepwalking.

Usually, no specific treatment is necessary unless sleepwalking results in injury.

The following general measures may help make sleepwalking less likely:

  • Taking measures to improve sleep—for example, near bedtime, avoiding doing anything stimulating (such as exercising or consuming caffeine)

  • Installing alarms to awaken the sleepwalker when the sleepwalker leaves the bed

  • Installing door alarms

The following measures may help prevent injuries during sleepwalking:

  • Gently leading the sleepwalker back to bed, rather than forcibly awakening the sleepwalker, which may agitate the sleepwalker

  • Removing obstacles or breakable objects that may be in the sleepwalker's path

  • Keeping windows closed and locked

  • For the sleepwalker, sleeping in a low bed or on a mattress on the floor to prevent falls from bed when the sleepwalker attempts to get out of bed

Rapid eye movement sleep behavior disorder

This disorder involves speaking (often profanely) and sometimes making aggressive movements during rapid eye movement (REM) sleep, usually in response to a dream.

People with REM sleep behavior disorder, unlike those with night terrors, are sometimes aware of having dreamed vividly during these episodes when they wake up the next day.

Aggressive movements may include waving the arms, punching, and kicking. The aggressive behavior is not intentional and is not directed at anyone. People may inadvertently injure themselves or their bed partner. Also, this behavior interferes with sleep, making people tired and sleepy during the day.

To check for disorders that cause degeneration of the brain, doctors do a neurologic examination Neurologic Examination When a neurologic disorder is suspected, doctors usually evaluate all of the body systems during the physical examination, but they focus on the different parts of the nervous system. Examination... read more to evaluate mental status and brain and nerve function. If an abnormality is detected, computed tomography (CT) or magnetic resonance imaging (MRI) may be done.

There is no cure for the disorder. But clonazepam, a benzodiazepine (which is a sedative), relieves symptoms in most people. A low dose is effective. The drug is usually continued indefinitely. Melatonin may also help relieve symptoms of REM sleep behavior disorder.

Bed partners should be warned about the possibility of harm and may wish to sleep in another bed until the drug begins to work. People with REM sleep behavior disorder should remove sharp objects and furniture from next to their bed.

Sleep-related leg cramps

Doctors usually diagnose sleep-related leg cramps based on symptoms after they rule out other physical problems or disabilities. No further testing is needed.

To prevent these cramps, people should stretch the affected muscles for several minutes before going to sleep. Usually, stretching as soon as cramps occur relieves symptoms promptly and is preferred to drug treatment. Avoiding caffeine and other stimulants may help.

Many drugs (such as quinine, calcium and magnesium supplements, diphenhydramine, benzodiazepines, and mexiletine) have been used, but none is likely to be effective. Also, side effects, especially with quinine and mexiletine, may be bothersome.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Diastat, Dizac, Valium, VALTOCO
Ceberclon , Klonopin
Niravam, Xanax, Xanax XR
Cafcit, NoDoz, Stay Awake, Vivarin
Aid to Sleep, Alka-Seltzer Plus Allergy, Aller-G-Time , Altaryl, Banophen , Benadryl, Benadryl Allergy, Benadryl Allergy Children's , Benadryl Allergy Dye Free, Benadryl Allergy Kapgel, Benadryl Allergy Quick Dissolve, Benadryl Allergy Ultratab, Benadryl Children's Allergy, Benadryl Children's Allergy Fastmelt, Benadryl Children's Perfect Measure, Benadryl Itch Stopping, Ben-Tann , Children's Allergy, Compoz Nighttime Sleep Aid, Diphedryl , DIPHEN, Diphen AF , Diphenhist, DiphenMax , Dytan, ElixSure Allergy, Genahist , Geri-Dryl, Hydramine, Itch Relief , M-Dryl, Nighttime Sleep Aid, Nytol, PediaCare Children's Allergy, PediaCare Nighttime Cough, PediaClear Children's Cough, PHARBEDRYL, Q-Dryl, Quenalin , Siladryl Allergy, Silphen , Simply Sleep , Sleep Tabs, Sleepinal, Sominex, Sominex Maximum Strength, Theraflu Multi-Symptom Strip, Triaminic Allergy Thin Strip, Triaminic Cough and Runny Nose Strip, Tusstat, Unisom, Uni-Tann, Valu-Dryl , Vanamine PD, Vicks Qlearquil Nighttime Allergy Relief, Vicks ZzzQuil Nightime Sleep-Aid
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