This site is intended for healthcare professionals

Go to /sign-in page

You can view 5 more pages before signing in


Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Parasomnias are unusual episodes or behaviours occurring during sleep which disturb the patient or others

  • violent or unusual night-time attacks may arise from deep non-Rapid eye movement (REM) sleep (night terrors and sleepwalking) or from REM sleep [sleep paralysis, severe recurrent nightmares, REM behaviour disorder(RBD)]
  • treatments depend on which disorder is present

Diagnosis of parasomnias

  • assessment of parasomnia may be possible with a detailed history from patient or witness, but in general for adequate diagnosis, referral to a specialist sleep centre for polysomnography and video recording may be necessary especially for RBD where loss of REM atonia is seen


  • sleep consists of two strikingly different states:
    • Rapid eye movement sleep (REM) and non-rapid eye movement sleep (NREM), which alternate in a cyclical fashion
      • sleep begins with a “shallow” Stage 1 of NREM and “deepens” to NREM Stages 2, 3, and 4
        • which are followed by the first brief episode of REM in approximately 90 minutes
      • after the first sleep cycle, NREM and REM sleep continue alternating in a cyclical fashion
        • duration of each cycle is approximately 90 minutes
      • stages 3 and 4 of NREM sleep (also known as deep sleep, delta sleep, or slow wave sleep) predominate during the first third of the night
      • REM sleep episodes become longer as the night progresses, and the longest REM periods are found in the last third of the night


Related pages

Create an account to add page annotations

Add information to this page that would be handy to have on hand during a consultation, such as a web address or phone number. This information will always be displayed when you visit this page