Carolinas Medical Center

Sleep disorders - overview


Sleep disorders are problems with sleeping. These include:

  • Trouble falling or staying asleep
  • Falling asleep at the wrong times
  • Too much sleep
  • Abnormal behaviors during sleep


There are more than 100 different sleeping and waking disorders. They can be grouped into four main categories:

  • Problems falling and staying asleep (insomnia)
  • Problems staying awake (excessive daytime sleepiness)
  • Problems sticking to a regular sleep schedule (sleep rhythm problem)
  • Unusual behaviors during sleep (sleep-disruptive behaviors)


Insomnia includes trouble falling asleep or staying asleep. Episodes may come and go, last up to 3 weeks (be short-term), or be long-lasting (chronic).


People with excessive daytime sleepiness feel tired during the day. Symptoms that are not caused by a lack of sleep or interrupted sleep are called hypersomnia.

Causes of this problem include:

  • Medical conditions, such as fibromyalgia and low thyroid function
  • Mononucleosis or other viral illnesses
  • Narcolepsy and other sleep disorders
  • Obesity, especially if it causes obstructive sleep apnea

When no cause for the sleepiness can be found, it is called idiopathic hypersomnia.


Problems may also occur when you do not stick to a regular sleep and wake schedule. This occurs when people travel between time zones and with shift workers who are on changing schedules, especially nighttime workers.

Disorders that involve a disrupted sleep schedule include:

  • Irregular sleep-wake syndrome
  • Jet lag syndrome
  • Paradoxical insomnia (the person sleeps a different amount than they think they do)
  • Shift work sleep disorder


Abnormal behaviors during sleep are called parasomnias. They are fairly common in children and include:

  • Sleep terrors
  • Sleepwalking
  • REM sleep-behavior disorder (a person moves during REM sleep and may act out dreams)


Sateia MJ. International classification of sleep disorders-third edition: highlights and modifications. Chest. 2014;146:1387-1394. PMID 25367475

Wakefield TL, Lam DJ, Ishman SL. Sleep apnea and sleep disorders. In: Flint PW, Haughey BH, Lund VJ, et al., eds. Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Philadelphia, PA: Elsevier Mosby; 2015:chap 18.

Review Date: 2/2/2015
Reviewed By: Andrew Schriber, MD, FCCP, Specialist in Pulmonary, Critical Care, and Sleep Medicine, Virtua Memorial Hospital, Mount Holly, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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