Insomnia is defined as inadequate or poor-quality sleep. Types of insomnia include:

  • Transient insomnia—lasts from one night to a few weeks
  • Intermittent insomnia—happens from time to time
  • Chronic insomnia—happens on most nights and lasts a month or more

Insomnia may take the form of difficulty falling asleep, or middle-of-the-night or early-morning awakening.

Over the course of a year about one third of adults experience some level of insomnia, and 10%-15% have more severe or chronic insomnia. Insomnia may cause problems during the day, such as tiredness, a lack of energy, difficulty concentrating, and irritability. Insomnia is not a disease. Instead, it is a result of a behavior or a symptom of an underlying mental or physical problem. There are many causes of insomnia.

Transient and intermittent insomnia generally occur in people who are temporarily experiencing one or more of the following:

  • A life crisis or stress
  • A change in the sleep environment, including factors such as noise, light, or temperature
  • Sleep/wake schedule problems, such as those due to jet lag or temporary shift work
  • Side effects of medication

Chronic insomnia often results from a combination of factors. Medical conditions or factors that may disrupt sleep include:

Chronic insomnia may also be due to behavioral factors. These include:

  • Misuse of nicotine, caffeine, alcohol, or other substances
  • Disrupted sleep/wake cycles from shift work or other nighttime activity schedules
  • Chronic stress

For some people, insomnia is aggravated by:

  • Changes in time zone after a long flight (‘jet lag’)
  • Expecting to have difficulty sleeping and worrying about it
  • Excessive napping in the afternoon or evening

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