Insomnia, or trouble sleeping, is a sleep disorder in which there is an inability to fall asleep or to stay asleep as long as desired.[1][2] While the term is sometimes used to describe a disorder demonstrated by polysomnographic or actigraphic evidence of disturbed sleep, this sleep disorder is often practically defined as a positive response to either of two questions: "Do you experience difficulty sleeping?" or "Do you have difficulty falling or staying asleep?"[2]
Insomnia is most often thought of as both a medical sign and a symptom[2][3] that can accompany several sleep, medical, and psychiatric disorders characterized by a persistent difficulty falling asleep and/or staying asleep or sleep of poor quality. Insomnia is typically followed by functional impairment while awake. Insomnia can occur at any age, but it is particularly common in the elderly.[4] Insomnia can be short term (up to three weeks) or long term (above 3–4 weeks); it can lead to memory problems, depression, irritability and an increased risk of heart disease and automobile related accidents.[5]
Insomnia can be grouped into primary and secondary, or comorbid, insomnia.[6][7][8] Primary insomnia is a sleep disorder not attributable to a medical, psychiatric, or environmental cause.[9] It is described as a complaint of prolonged sleep onset latency, disturbance of sleep maintenance, or the experience of non-refreshing sleep.[10] A complete diagnosis will differentiate between free-standing primary insomnia, insomnia as secondary to another condition, and primary insomnia co-morbid with one or more conditions.
Cognitive behavioral therapy is useful in insomnia that is present for a long duration.[11] Those who are having trouble sleeping sometimes turn to sleeping pills, which may help, but also may lead to substance dependency or addiction if used regularly for an extended period.[12]