Glossary

Here are definitions of medical terms related to insomnia.

Early morning awakening: A sleep disorder in which people fall asleep normally but wake up several hours after and are unable to fall asleep again.

Insomnia: An ongoing inability to sleep or to remain asleep throughout the night.

Melatonin: A hormone (a chemical produced by the body and carried by the bloodstream to another part of the body to stimulate or retard its function) produced in the hypothalamus of the brain that causes a drop in body temperature and sleepiness.

Non-rapid eye movement (NREM) sleep: The early stages of sleep.

Rapid eye movement (REM) sleep: A stage of deep sleep marked by movement of the eye muscles; dreaming occurs during REM sleep.

Sleep apnea: A sleep disorder characterized by periods when breathing temporarily stops; the person is momentarily unable to move respiratory muscles or maintain an air flow through the nose and mouth.

Sleeping pill: A sedative, usually available over the counter, that is taken for insomnia.