The term parasomnia covers a variety of unusual physiological and behavioural phenomena which can occur during sleep, ranging from unusual movements and behaviours to dreams/nightmares, night terrors, sleep-walking and sleep-talking. Most parasomnias are intermittent and benign; however, some can pose a significant problem to an individual's health and safety.

Parasomnias can be classified as primary (occurring in their own right), or as secondary (meaning that they occur because of another medical condition). Most parasomnias are disorders of arousal, partial arousal or sleep-stage transition.

Parasomnias that can occur during non-REM (non-dream) sleep include:

  • Sleep-walking: this is common in children and most will grow out of the condition. Sleep-walking occurs in approximately 4% of adults and may precede the onset of certain degenerative brain disorders
  • Confusional arousal: this is common in children and is characterised by moving around excessively in bed, thrashing about or crying. This condition occurs also in approximately 4% of adults
  • Night terrors: usually very loud screaming, followed by extreme panic and violent behaviour (such as punching/kicking a wall, running around). The patient is nearly always inconsolable for a period of time. Subsequent amnesia for the event is common. This condition occurs in approximately 4% of adults
  • Sleep-sex: undesirable sexual activities during night, probably occurring in states between sleep and awake
  • Sleep-related eating disorder: repeated episodes of eating at night-time without awareness on the part of the patient.

Parasomnias that can occur during REM (dream) sleep include:

  • REM sleep behaviour disorder: abnormal movements during REM sleep, caused by failure of the brain to block motor signals to body muscles during dream sleep. This condition is discussed in more detail here
  • Nightmares: dreams of violent or horrific nature. Although nightmares are experienced by most people at some time, they can constitute a medical problem when they are recurrent. Some research has suggested a genetic basis for nightmares. Personality and emotional factors predispose to nightmares. Nightmares can be triggered by certain medications, illicit substances and alcohol. They can also be associated with mental illness, narcolepsy, and post-traumatic stress disorders (PTSD). Treatment for nightmares is individualised
  • REM-sleep-related cardiac dysrhythmias: there have been documented cases of sinus arrest during REM sleep in healthy individuals, independent of known heart problems or sleep-related breathing-disorder (such as obstructive sleep apnoea)
  • Impaired sleep-related penile erections

Other parasomnias include:

  • Bruxism: grinding or clenching of teeth during sleep. Click here for more information on bruxism.
  • Sleep-talking (somniloquy): talking during sleep is common in the population, and a genetic link has been identified. There is no evidence that this condition is either sinister in nature, or that it is linked to psychological illness
  • Catathrenia: catathrenia is groaning during sleep. The groaning often occurs intermittently. It often starts in childhood and continues into adulthood, but is often not noticed until early adulthood when the sufferer has sleeping partners (or sleeps in a dormitory-like environment). There is no known treatment and there is no evidence that this is a sinister condition
  • Enuresis: this is the medical term for bed wetting. It may occur during REM or NREM sleep. This condition is common in children. Most children grow out of the condition, however 1 - 2% of 18-year-olds and around 0.5% of adults have the problem. Nocturnal enuresis may be indicative of obstructive sleep apnoea, epilepsy or seizures occurring at night-time, or endocrine dysfunction. Treatment for enuresis is individualised
  • Movement disorders: such as Rhythmic Movement Disorder (RMD, also called jactatio capitis nocturna, is characterised by head-banging movements during sleep), and propriospinal myoclonus (a spinal cord movement disorder).

Secondary parasomnias:

These can occur secondary to conditions relating to other organ systems.

Examples include:

  • Nocturnal panic attacks, depressive or psychotic episodes
  • Muscle cramps and spasms
  • Paraesthesiae (tingling, numbness, 'pins and needles' sensations)
  • Seizures, convulsions, fits and 'funny turns'
  • Headaches/migraines/exploding head syndrome/cluster headaches
  • Tinnitus and hearing problems
  • Vertigo (including Benign Paroxysmal Positional Vertigo - BPPV)
  • Cardiac dysrhythmias, (including atrial fibrillation), palpitations, angina (chest pains)
  • Abnormal swallowing, hiccups during sleep, gastrointestinal problems (including gastro - oesophageal reflux disease - GORD)
  • Night sweats, dermatological (skin) disorders
  • Post-traumatic stress disorder
  • Asthma and other night-time respiratory problems
  • Tongue-biting