Insomnia is a common clinical problem for many individuals. It may be related to other comorbid conditions such as: mood disorders or psychiatric disease, medical conditions (cardiac, thyroid, menopausal, neurologic and age related). Insomnia is also a common sequela of other sleep disorders such as narcolepsy, sleep apnea, restless leg syndrome and circadian rhythm disorders. Its evaluation requires a careful and detailed history. Its essential elements include: persistent sleep disturbances in light of adequate opportunities for sleep and excessive day time sleepiness.

Insomnia is characterized as difficulty with initiating sleep, maintaining sufficient sleep duration and problems consolidating sleep with poor sleep quality. Studies have demonstrated elevated heart rate, basal skin resistance, core body temperature, increased metabolic activity and phasic vasoconstriction in some subjects with chronic insomnia. If left untreated, chronic insomnia may predispose a greater risk for developing medical complications related to the immune system, cardiovascular disease and endocrine function.