Parasomnias are a pattern of sleep disorders marked by unusual actions, activities, or physiological events that occur during sleep or sleep-wake transitions. Parasomnias are divided into which sleep phase the symptoms occur, either rapid eye movement (REM) or non-REM (NREM). Symptoms may include simple or complex abnormal movements, such as sleep talking, sleepwalking, sleep terrors, and dream enactment, or emotions, dreams, and autonomic activity. Diagnosis involves a thorough history taking from the patient and the partner. In some cases, polysomnography is required, especially if comorbid sleep disorders are suspected. Some conditions resolve over time without any treatment. For those that require intervention, options include lifestyle or risk modifications, different forms of therapy, and medications. Choice of management is affected by patient preferences.

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Parasomnias are abnormal behaviors, actions, or activities occurring during sleep.


Sleep disorders are generally divided into the following groups:

  • Parasomnias, which have subtypes according to each sleep stage:
    • Non-rapid eye movement (NREM) sleep arousal disorders: 
      • Sleepwalking (somnambulism)
      • Sleep terrors
      • Sleep-related eating disorders 
      • Confusional arousals
      • Sleep-related abnormal sexual behavior
    • Rapid eye movement (REM) sleep arousal disorders:
      • REM sleep behavior disorder (RBD) 
      • Nightmare disorder
  • Dyssomnias, which are abnormalities in the amount, quality, or timing of sleep; the subtypes are:
    • Insomnia disorder
    • Narcolepsy
    • Circadian rhythm sleep-wake disorders
    • Sleep apnea

Etiology and Epidemiology


  • Theory on dissociation of states of consciousness consisting of wakefulness, NREM, REM sleep: combinations of these states → parasomnias
  • NREM-related disorders:
    • NREM generally exhibits instinctive actions, which would normally be inhibited in wakefulness. 
    • In NREM subtypes, there is an admixture of wakefulness and NREM.
    • Increased slow-wave sleep in NREM (difficult to arouse) noted, but there is potential for motor capacity
    • Factors:
      • Genetic predisposition
      • Conditions (stress, sleep deprivation, fever) 
      • Substances (alcohol, medications such as zolpidem are associated with sleep-related eating disorder) 
  • REM-related disorders:
    • Mix of wakefulness and elements of REM
    • Believed to have degeneration of cells involved in the normal REM sleep pathway 


  • NREM sleep disorders are more common in a younger demographic whereas REM sleep disorders are more common in an older demographic.
  • REM sleep disorder is more common among men, especially in the older demographic.
  • Sleep-related eating disorder mostly occurs among women.
  • High prevalence of RBD in those with Parkinson disease

Clinical Presentation and Diagnosis

Clinical features of NREM-related parasomnias

  • Sleepwalking:
    • Episodes of simple to complex movements
    • May include sitting in bed, walking, eating, going outdoors, and, in rare cases, violent behaviors
    • Difficult to arouse during episode (eyes might be open with a blank stare)
    • Failure to recall the episode (amnesia)
    • Episodes might end with patients returning to bed or briefly awakening (confused and disoriented).
  • Sleep terrors:
    • Marked by sudden arousals, beginning with screaming or crying
    • Associated with autonomic changes (tachycardia, tachypnea, diaphoresis, mydriasis)
    • Difficult to arouse during episode (not responsive)
    • Amnesia or partial dream recollection afterwards
    • Episodes end with patients returning to sleep.
    • Most common in children
  • Sleep-related eating disorder:
    • Recurring episodes of involuntary eating after being aroused from sleep
    • Possible partial awareness during the event
    • May have partial recollection of event
    • Criteria specify that episodes have to include the following:
      • Consuming toxic food, or
      • Engaging in potentially injurious behaviors while obtaining food, or 
      • Adverse health effects from chronic nighttime eating
  • Confusional arousals:
    • Mental confusion or disorientation on awakening (from slow-wave sleep), usually lasting < 15 minutes
    • Awake patient but with reduced responsiveness
    • Typically without recall of event
  • Sleep-related abnormal sexual behavior (sexsomnia):
    • Can occur with obstructive sleep apnea
    • Abnormal sexual behaviors (without awareness and typically without recall) can include:
      • Masturbation 
      • Sexual intercourse with partner
      • Sexual assault

Clinical features of REM-related parasomnias

  • RBD:
    • Dream-enacting behaviors include:
      • Sleep talking or yelling
      • Limb jerking
      • Walking and/or running
      • Punching and/or other violent behaviors
    • Episodes of arousal during sleep
    • Characterized by a lack of muscle atonia during REM sleep 
    • With recollection of dream content 
    • Upon awakening, often alert but can be briefly disoriented
    • Presenting complaint is often made by the patient’s partner (reporting violent behaviors during sleep resulting in injury to the partner).
    • Commonly seen in:
      • Elderly patients 
      • Patients taking certain medications (serotonergic antidepressants and beta-blockers)
      • Those with neurodegenerative disorders (Parkinson disease, multiple system atrophy, and neurocognitive disorder with Lewy bodies)
  • Nightmare disorder:
    • Recurrent episodes of vivid dreams (with scary, negative themes)
    • Not associated with motor activity or sleep injury
    • Episodes end with patients awakening and recalling the unpleasant dream. 
    • Patient is fully alert upon awakening (no confusion or disorientation).
    • Causes significant distress or impaired functioning
    • Not associated with medication or substance use

Diagnostic approach

  • NREM parasomnias can often be diagnosed from history taking from the patient or their partner. 
  • Nightmare disorder is also a clinical diagnosis.
  • In conditions above, suspicion of comorbid sleep disorder (e.g., obstructive sleep apnea (OSA)) requires polysomnography.
  • In RBD, detailed history is helpful, but video polysomnography is required for a definitive diagnosis.


  • Non-REM parasomnias:
    • Patients with mild symptoms may benefit from behavioral therapy:
      • Sleep hygiene
      • Education (patient and partner) and reassurance
    • Risk factor modification (e.g., discontinue medication)
    • Ensure environmental safety (e.g., secure locks, remove dangerous objects)
    • Treat coexisting sleep disorders.
    • Refractory cases (frequent, persistent, and distressing) might benefit from a short course of benzodiazepines such as clonazepam. 
    • In addition, the following pharmacotherapy are options:
      • Selective serotonin reuptake inhibitors (SSRIs): sleep-related abnormal sexual behavior and sleep-related eating disorder
      • Topiramate: sleep-related eating disorder
  • REM sleep behavior disorder:
    • Risk factor modification
    • Ensure environmental safety around the patient (remove any dangerous objects near place of sleep).
    • Medications that might be helpful: 
      • Clonazepam is efficacious in 90% of patients.
      • Melatonin 
  • Nightmare disorder:
    • Reassurance might be enough.
    • Desensitization/imagery rehearsal therapy (IRT) involves:
      • Use of mental representation to modify the result of a recurrent nightmare
      • Writing down the improved outcome
      • Mentally repeating it in a relaxed state
    • Medications (e.g., prazosin, antidepressants) may be indicated if nightmare disorder is associated with PTSD or other psychiatric disorder(s).

Differential Diagnosis

  • Restless legs syndrome: marked by an overwhelming urge to move the legs, accompanied by unpleasant sensations, which are relieved by movement. Symptoms usually occur during the evening and cause sleep disturbance. Patients are aware of restless legs causing distress, while they are not usually aware of parasomnias.
  • OSA: episodic apnea, or cessation of breathing during sleep, in which the period of apnea lasts for more than 10 seconds. Obstructive sleep apnea is usually due to a partial or complete collapse of the upper airway and is associated with snoring, restlessness, daytime headache, and somnolence. Obstructive sleep apnea is much more prevalent than parasomnias and must be ruled out. 
  • Nocturnal seizures: should be excluded in patients with suspected parasomnias. Symptoms of nocturnal seizures include repetitive stereotypical movements (tonic or dystonic), occurring at any time during sleep. Episodes are usually short in duration (≤ 30 seconds).


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