A coma is a state of total unconsciousness that lasts more than six hours. A person in a coma cannot be woken up, has depressed reflexes, has no movement in the limbs other than reflex-based movements, does not respond to pain or other physical stimuli, and may have irregular breathing patterns. Comas are classified according to the area of the brain in which the coma originates, but the classification has no relation to prognosis.

What Causes Comas?

A coma is typically caused by problems in the brain. A blow to the head, a brain infection, brain tumors, stroke, seizures, and toxic substances may induce comas. Excessive ingestion of alcohol or drugs can also result in a coma, and are among the most common causes of comas. Doctors can also medically induce a coma. This procedure is typically reserved for people whose bodies need to heal from a serious illness or injury without excessively taxing their systems.

Treatment and Prognosis

Most people spontaneously awake from comas within several days or weeks. Treatment typically depends upon the cause of the coma. Doctors may give large doses of antibiotics if a brain infection is suspected and may perform surgery to treat brain injuries. Doctors also provide treatment to keep the person alive while he/she is in the coma. These treatments may include providing fluids and nutrition through an IV, putting the person on a ventilator, and carefully monitoring the heart rate. People who awaken from comas may return to normal functioning or may suffer prolonged brain damage.

A person who remains in a coma for more than a few weeks may be classified as being in a persistent vegetative state. While people can wake up from this state, it is less likely than waking from a coma, and few people who are in a persistent vegetative state for more than three years awaken. A persistent vegetative state can lead to brain death, but people in persistent vegetative states are not necessarily brain dead.


  1. Coma information page. (n.d.). Coma Information Page: National Institute of Neurological Disorders and Stroke (NINDS). Retrieved from
  2. Mayo Clinic Staff. (2010, May 08). Coma. Mayo Clinic. Retrieved from

Last Updated: 08-4-2015

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