the inability to sleep adequately. Causes may include poor sleeping conditions, circulatory (cardiovascular disease) or brain disorders, a respiratory disorder known as apnea, stress, or other physical or mental disorders. Insomnia is not harmful if it is only occasional; the body is readily restored by a few hours of extra sleep. If, however, it is regular or frequent, insomnia may have harmful effects on other systems and functions of the body.

Treatment of mild insomnia may involve simple improvement of sleeping conditions or such traditional remedies as warm baths, warm milk, or relaxation. Chronic insomnia may require the temporary use of sedatives (sedative-hypnotic drug), hypnosis, or psychotherapy; apnea and its associated insomnia may be treated surgically. The prolonged use of sleeping pills as a relief from frequent or recurring insomnia can have harmful effects. The body tends to build up a tolerance to the medication, necessitating a more potent dosage in order to fall asleep; habitual use can lead to addiction.