Insomnia is defined as inadequate or poor-quality sleep despite having adequate time to sleep. Insomnia may take the form of difficulty falling asleep, or middle-of-the-night or early-morning awakening. It may be a short-term problem or occur more often over a long period of time. It becomes more common as you get older.

Over the course of a year, about one third to one half of adults experience some level of insomnia. About 10%-15% have more severe or chronic insomnia. It 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.

Short-term insomnia is often due to temporary situations. It generally occurs in people who are 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 with jet lag or temporary shift work
• Side effects of medication

Chronic insomnia often results from a medical condition. Examples include:

• Depression
• Anxiety
• Arthritis
• Manic disorders
• Conditions that cause chronic pain
• Kidney disease
• Heart failure
• Asthma
• Sleep apnea
• Narcolepsy
• Restless legs syndrome
• Parkinson's disease
• Dementia or Alzheimer disease
• Hyperthyroidism
• Gastroesophageal reflux disease (GERD)
• Pregnancy
• Menopause
• Sickle cell disease

Chronic insomnia may caused by lifestyle or behavioral factors. These may 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 2 common responses:

• Expecting to have difficulty sleeping and worrying about it, or
• Excessive napping in the afternoon or evening