Insomnia is defined as having trouble falling asleep or staying asleep,
or as having unrefreshing sleep despite having ample opportunity to
sleep. Life is filled with events that occasionally cause insomnia for
a short time. Such temporary insomnia is common and is often
brought on by situations such as stress at work, family pressures, or
a traumatic event. A National Sleep Foundation poll of adults in the
United States found that close to half of the respondents reported
temporary insomnia in the nights immediately after the terrorist
attacks on September 11, 2001.
Chronic insomnia is defined as having symptoms at least 3 nights
per week for more than 1 month. Most cases of chronic insomnia
are secondary, which means they are due to another disorder or
medications. Primary chronic insomnia is a distinct sleep disorder;
its cause is not yet well understood. About 30–40 percent of adults
say they have some symptoms of insomnia within any given year,
and about 10–15 percent of adults say they have chronic insomnia.
Chronic insomnia becomes more common with age, and women are
more likely than men to report having insomnia.
Insomnia often causes problems during the day, such as extreme
sleepiness, fatigue, a lack of energy, difficulty concentrating,
depressed mood, and irritability. Thus, untreated insomnia can
impair quality of life as much as, or more than, other chronic
medical problems