<p>A coma is a deep state of unconsciousness. An individual in a coma is alive but unable to move or respond to his or her environment. Coma may occur as a complication of an underlying illness, or as a result of injuries, such as <a href="https://medlineplus.gov/traumaticbraininjury.html">brain injury</a>.</p> <p>A coma rarely lasts more than 2 to 4 weeks. The outcome for coma depends on the cause, severity, and site of the damage. People may come out of a coma with physical, intellectual, and psychological problems. Some people may remain in a coma for years or even decades. For those people, the most common cause of death is infection, such as pneumonia.</p> <p class="">NIH: National Institute of Neurological Disorders and Stroke</p>