Insomnia — difficulty falling, staying asleep or waking too early and not being able to get back to sleep - is one of the most common sleep problems. More than half (54 percent) of Americans said they experience at least one symptom of insomnia at least a few nights a week. Additionally, one in five adults experienced difficulty falling asleep, and one in three reported waking too often during the night at least a few nights a week.

Insomnia has many causes and may be a symptom of some underlying problem. Healthcare professionals find it useful to categorize insomnia by duration of the symptoms:

• Transient insomnia — lasts no more than a few nights and is usually triggered by short-term stress (e.g., a job interview), excitement or changes in sleep schedule or environment.
   
• Short-term insomnia — lasts no more than a few weeks and is usually associated with ongoing stressful events (e.g., divorce or moving to a new city), psychological trauma or illness. It is common for episodes to recur.
   
• Long-term or chronic insomnia — lasts more than a month, with poor sleep occurring every night, most nights or several nights per month. There may be underlying behavioral, medical or psychiatric problems, such as depression.

What Are the Effects of Sleep Loss?

A lack of restful sleep can negatively impact an individual's waking hours. Lost sleep can result in a reduced ability to concentrate, excessive daytime sleepiness, and irritability. While not all sleep loss is attributable to insomnia, sleep deprivation can impair the ability to perform both physical and mental tasks.

• There’s more to chronic insomnia than feeling drowsy in the morning. It can actually impair your functioning by causing a decreased ability to concentrate, memory loss, fatigue, and diminished motivation. It can also impair your coordination and motor functioning, and lead to an increased risk of accidents when you’re driving or even just walking. Evidence also suggests that insomnia is associated with many other serious medical conditions, and may increase the risk of developing certain psychiatric disorders, particularly depression and anxiety.
   
• Chronic insomnia may impair your normal functioning in a number of ways, causing both cognitive and physical problems. Research has shown that insomnia can decrease your memory function, motivation and concentration, as well as cause fatigue. Chronic insomnia may also increase your risk of accidents, such as driving accidents or falls. Additionally, insomnia is associated with a number of other medical conditions, and may even increase the risk of developing certain psychiatric disorders, particularly depression and anxiety.

What Are Some of the Causes of Insomnia?

• Lifestyle factors — Many behaviors can create or worsen sleeping problems. Smoking and drinking caffeinated beverages, for example, interfere with sleep because they involve intake of stimulants such as nicotine and caffeine, which promote wakefulness. Alcohol intake close to bedtime may also result in disruption of normal sleep patterns. Other lifestyle factors that can contribute to poor sleep include physical activity too close to bedtime and erratic sleep schedules. For example, shift workers often find sleep particularly challenging because they have to sleep during daylight hours when biological rhythms encourage wakefulness.
   
• Environmental factors — Noise, such as that from passing traffic, airplanes or a neighbor's television, can disturb sleep. Too much light or a sleeping environment that is too hot or too cold also can interfere with sleep.
   
• Medical factors — Kidney disease, heart failure, asthma and Parkinson's disease can impair healthy sleep. Conditions that cause pain or discomfort, such as arthritis, can also make it difficult to sleep well.
   
• Psychological/psychiatric factors — Most sleep experts consider stress to be the most common cause of short-term sleeping difficulties. School- or job-related pressures, family or marriage problems, or a serious illness or death in the family are common triggers. Insomnia can be a component of depression.

National Sleep Foundation Polls

According to NSF polls dating back to 1999, over 1/2 of America's adults experience one or more symptom of insomnia at least a few nights a week. In 2005, the following percentages of adults reported having the following symptoms this often:  38% woke up feeling unrefreshed; 32% wake often during the night; and 21% of the population reports waking too early, not being able to get back to sleep and difficulty falling asleep. Of this last group, almost 1/4 state that it takes them at least 30 minutes to fall asleep. These people are likely to be women (28% vs. 16%) and not to have a bed partner (27% vs. 19%). 

People who drink >4 caffeinated beverages a day are more likely to have difficulty falling asleep and wake unrefreshed. Those who are obese are more likely to have a symptom of insomnia. Adults who have daytime sleepiness at least 3 times a week are experiencing a symptom of insomnia (86%) compared to those who rarely or never have such symptoms (31%). This is also true for those who say sleepiness has a strong impact on their daily activities (83%) versus those who experience very little impact (44%). More people who take >2 naps a day report symptoms of insomnia (62%) compared to those who do not take a nap (48%).