Northside Health Library

Sleep disorders - overview


Sleep disorders are problems with sleeping, including trouble falling or staying asleep, falling asleep at the wrong times, too much sleep, or 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:

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:

Review Date: 8/16/2011
Reviewed By: David B. Merrill, MD, Assistant Clinical Professor of Psychiatry, Department of Psychiatry, Columbia University Medical Center, New York, NY. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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