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What Is Insomnia?

When Trouble Falling or Staying Asleep is a Disorder


Updated November 06, 2013

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

What Is Insomnia?
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Though it is one of the most common of sleep disorders, one may wonder: What is insomnia? It is important to understand what insomnia is, how often it occurs, and its classic clinical features.

Defining Insomnia

Insomnia is an inability to obtain a sufficient amount of sleep to feel rested. It can be characterized either by difficulty falling or staying asleep. In addition, the sleep itself may be chronically of poor quality. In order for insomnia to be present, the above difficulties must occur despite adequate opportunity for sleep, so that it is not due to sleep deprivation. In addition, the impairment must lead to problems with daytime functioning.

The degree of sleep disturbance may vary, but insomnia typically involves taking 30 or more minutes to fall asleep or a total sleep time that is less than six hours, three or more nights per week.

How Common Is Insomnia?

Insomnia is perhaps the most common sleep disorder. Just how frequently it occurs depends on the study, the definition used, and whether one is assessing chronic versus intermittent or acute insomnia. In one study, 35% of adults reported insomnia of any type during the previous year. Approximately 10% of people have chronic insomnia that affects their daytime functioning, according to a review of 50 studies.

In addition, insomnia more commonly occurs as we get older. Women in particular are more likely to report insomnia symptoms. Insomnia also seems to be more common among those who are unemployed, single (from any cause), or of low socioeconomic status.

Symptoms of Insomnia

Patients with insomnia may experience numerous symptoms, including:

  • Fatigue or daytime sleepiness
  • Poor attention or concentration
  • Reduced energy or motivation
  • Problems with work or social life
  • Mood problems, including anxiety and depression
  • Suicide risk
  • Headache

Causes of Insomnia

Factors that may potentially contribute to developing insomnia include travel, noise, family responsibilities (including caring for infants), pain, stress, or nocturia (getting up during the night to urinate).

As with any medical condition, it is important to rule out other potential causes of insomnia. In individuals with symptoms suggestive of insomnia, it is necessary to assess whether other medical or psychiatric problems, medications, or substance use may be contributing to the condition. For anyone who simply is not getting enough sleep by choice, insomnia would not be the correct diagnosis.

Insomnia is a common condition that should be properly identified so that efforts can be made to provide adequate treatment and relief from a disorder that can lead to significant impairment of one’s life.


"International classification of sleep disorders: Diagnostic and coding manual." 2nd ed. American Academy of Sleep Medicine. Westchester, IL 2005.

Mellinger, GD et al. "Insomnia and its treatment: Prevalence and correlates." Arch Gen Psychiatry 1985; 42:225.

Ohayon, MM. "Epidemiology of insomnia: what we know and what we still need to learn." Sleep Med Rev 2002; 6:97.

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