Insomnia is characterized by inadequate or non-refreshing sleep, frequent wakning with difficulty falling back to sleep, difficulty falling asleep or waking too early. Inadequate amount of sleep or the lack or restful sleep impairs the person's ability to carry out their daily responsibilities because they are too tired or have trouble concentrating. About 10 to 15 percent of adults in industrialized countries indicate that their condition is severe or chronic (insomnia lasting more than four weeks). The prevalence of insomnia increases with age and is more common in women.

Insomnia has a variety of causes. It is often a symptom of some other disease or condition (e.g. life stress, psychiatric and medical disorders, or use of certain medications), but it can also be a distinct disorder (primary). Chronic insomnia is often associated with fatigue, mood changes, difficulty concentrating and impaired daytime functioning. A useful treatment would not only help the patients gain more sleep or better quality sleep at night but is also expected to improve daytime functioning. These therapeutic effects should be maintained upon long-term use.