Types and Causes of Insomnia

Reviewed by: HU Medical Review Board | Last reviewed: June 2020

Insomnia, or trouble falling asleep and staying asleep, is one of the most common sleep disorders in the United States. As many as half of people in the United States sometimes have insomnia symptoms. Experts believe 10 percent to 15 percent experience chronic insomnia.1,2

There are 2 types of insomnia:3

  • Short-term, or acute, insomnia which usually lasts for a few days or weeks
  • Chronic insomnia, which occurs at least 3 times a week for 3 months or longer

What is acute (short-term) insomnia?

Almost everyone experiences a sleepless night or two at some point in their lives. In fact, short-term insomnia impacts 30 to 50 percent of people.

This type of insomnia often happens during stressful times. Losing a job, worry about a family member, divorce, or getting bad news are all examples of life events that may disrupt sleep for a short time. Jet lag is another condition that may cause temporary insomnia.3,4

Normal sleep patterns usually return when the stress passes or the person adjusts to a new routine. However, short-term insomnia can become a long-term problem if poor sleep habits develop during this time.3

What is chronic (persistent) insomnia?

Long-term, or chronic, insomnia is less common. It happens to about 10 to 15 out of every 100 people. Doctors may diagnose chronic insomnia if the person has trouble falling or staying asleep for at least 3 nights a week for 3 months or longer. Chronic insomnia is more common in the elderly and people with certain health conditions.2,3,5

Other types of chronic insomnia are terminal insomnia and middle-of-the-night insomnia. Terminal insomnia means a person wakes up too early and cannot go back to sleep. Wake times are often 2 a.m. to 4 a.m. Middle-of-the-night insomnia means a person wakes many times in the middle of the night. In both types, the person may not have trouble falling asleep when they first go to bed.6

Types of long-term (chronic) insomnia

Chronic insomnia is divided into 2 types: primary and secondary.

Primary insomnia

Primary insomnia is insomnia with no known cause. Psychophysiological insomnia is one example of primary insomnia. With this type of insomnia, a person worries about not getting good sleep before they go to bed, which then leads to trouble falling or staying asleep. This type of insomnia is a learned behavior rather than insomnia with a physical cause.7

Idiopathic insomnia, another type of primary insomnia, is a neurological issue in which the brain does not properly control wake and sleep cycles. People with this type of insomnia often describe themselves as “light sleepers.”8

Some studies suggest that people with primary insomnia have consistently low melatonin levels and unusual vital signs during sleep.9

Secondary insomnia

Most people with chronic insomnia have what is called secondary insomnia. Secondary insomnia is sleeplessness caused by some other health issue.4

What causes secondary insomnia?

Chronic insomnia may come and go from night-to-night over years, depending on a person’s stress and overall health. Among the many health conditions that may lead to secondary insomnia are:3,4

  • Mental health issues such as depression, anxiety, and schizophrenia
  • Post-traumatic stress disorder (PTSD) or brain injury
  • Brain disorders such as stroke, Alzheimer’s or Parkinson’s disease
  • Asthma
  • Pregnancy
  • Menopause
  • Cancer
  • Thyroid problems
  • Autoimmune disorders
  • Chronic pain
  • Certain drugs

In some people, insomnia may be an early sign of developing major depression and other types of mental illness.

Family history and lifestyle issues

A personal or family history of insomnia and certain lifestyle issues may make a person more likely to develop insomnia. These include:10

  • Worry and stress
  • Living alone
  • Recreational drug use and alcoholism
  • Poor sleep habits

A range of common sleep habits may trigger insomnia or make it worse. These include:3

  • Drinking alcohol, consuming caffeine, or smoking close to bedtime
  • Exercising late in the day
  • Not keeping a regular sleep schedule

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