A coma is a prolonged state of unconsciousness. It occurs when a temporary or permanent disruption of the brain’s function severely affects consciousness. This damage results in:

  • unconsciousness
  • inability to awake
  • unresponsiveness to stimuli, such as pain, sound, and light

The word “coma” is derived from the Greek word “koma,” which means “deep sleep.”

A person who is in a coma is alive but unable to move at will. In most instances, they can’t think, speak, or respond to their environment. Important functions like breathing and blood circulation are impaired in most cases. A person can be supported with medication or other interventions, such as airway pressure or mechanical ventilation.

When a person has a sudden or gradual impairment of consciousness, healthcare professionals work quickly so the person will have the best outcome possible. If a person receives the diagnosis of a coma, it’s important to maintain organ support until they recover.

Some people wake up gradually from a coma, typically after a few weeks. Others, however, may remain in comas for years or even decades, kept alive by nutritional supplementation as well as breathing and heart function assistance.

A coma is diagnosed when a person has remained in a state of decreased consciousness and meets certain criteria, such as:

  • closed eyes
  • unresponsiveness
  • irregular breathing
  • no response of limbs, except for reflexes
  • no response to pain, except for reflexes

People in a coma may still swallow and cough on their own.

Sometimes, people in a coma can breathe without assistance, but other times, they need a machine, like a ventilator, to help them.

Comas are caused by damage to the brain, especially if there’s bilateral damage to the cerebral cortex (which means damage on both sides), or damage to the reticular activating system. The reticular activating system controls arousal and awareness of the cerebral cortex. Damage here can result from many potential factors, such as:

  • traumatic brain injuries, such as those caused by traffic accidents or violent trauma
  • stroke (reduced blood supply to the brain)
  • tumors in the brain or brainstem
  • lack of oxygen to the brain after being rescued from drowning or from a heart attack
  • unmanaged diabetes, which causes blood sugar levels to become too high (hyperglycemia) or too low (hypoglycemia) and can lead to swelling in the brain
  • overdosing on drugs or alcohol
  • carbon monoxide poisoning
  • buildup of toxins in the body, such as ammonia, urea, or carbon dioxide
  • heavy metal poisoning like lead
  • infections, such as meningitis or encephalitis
  • repeated seizures
  • electrolyte imbalance

For people in a coma, there are different levels of awareness, ranging from deep and unresponsive, to more shallow, when a person can open their eyes. These states are:

Persistent vegetative state. When someone is in a persistent vegetative state, they’re unaware of their surroundings and unable to move voluntarily. This condition can sometimes last indefinitely, and when it does, it’s called a permanent vegetative state.

Minimally conscious state. This state of consciousness sometimes occurs when someone comes out of a vegetative state. They have limited signs of awareness and can occasionally respond to stimuli or requests (“grab my hand,”), but it’s hard for them to retain consciousness for long periods.

Brain death. This is different from a coma and is not reversible. The definition of brain death includes specific criteria, such as a lack of certain reflexes. Several doctors will perform a medical examination to determine if the brainstem and cerebrum are functioning.

When someone has an impairment of consciousness, a healthcare professional will ask friends and family about any events or symptoms that led up to the coma. They’ll also ask for details about recent changes in the person’s life, medical history, and drug use. Drugs of concern include prescription drugs and over-the-counter drugs, as well as recreational drugs.

A physical exam will be conducted. This might include:

  • checking reflexes
  • checking muscle tone
  • checking blood pressure
  • observing breathing patterns and heart rhythm
  • checking for signs of bruises on the skin that may have been caused by trauma
  • determining the person’s response to painful stimuli
  • observing pupil size

Glasgow coma scale

During a physical examination, a doctor may use a scale, such as the Glasgow coma scale, to describe the symptoms. This way, the doctor can follow changes in a consistent manner and document whether a person’s level of consciousness is improving, stable, or getting worse. This type of system observes factors such as “verbal response” on the following scale:

  • 5 = oriented
  • 4 = confused
  • 3 = inappropriate words
  • 2 = incomprehensible sounds
  • 1 = no verbal response


When a person is not responsive and it’s not clear why, a medical professional can perform a variety of tests to look at the following:

  • urinalysis
  • blood count
  • thyroid and liver function
  • electrolyte levels
  • blood sugar levels
  • carbon monoxide poisoning
  • drug overdose
  • alcohol overdose
  • infections of the nervous system

Brain scans may also be done to locate the areas that have been injured, and to look for signs of brain hemorrhage, tumors, stroke, or seizure activity. Some of these brain scans are:

  • Computerized tomography (CT) scans. CT scans use X-rays to create a detailed image of the brain.
  • Magnetic resonance imaging (MRI). An MRI uses radio waves and magnets to view the brain.
  • Electroencephalography (EEG). An EEG measures electrical activity inside the brain.

The first priority of coma treatment is to minimize brain damage and to support the functions of the body.

If the cause of the coma is known, medications for treating the underlying condition will be administered, as in the case of a drug overdose or a brain infection.

Sometimes, surgery may be required to reduce swelling in the brain.

Once a person who is in a coma is stabilized, doctors will work to prevent infections, bedsores, and contractures of the muscles. The medical team will also make sure to provide the person with balanced nutrition during the coma.

Many times, a person will recover from a coma after a few weeks. The recovery is usually gradual.

When a person first gains consciousness, they may be agitated or confused. Talk with doctors or hospital staff about the best ways to communicate with a loved one as they gradually recover.

Some people recover from a coma without any lasting symptoms. Others many have lifelong conditions due to damage to their brain, and may need physical therapy or occupational therapy.

It’s not always possible to predict how well a person will recover from a coma, but there are a few factors that play into it, such as:

  • a person’s age
  • the severity and cause of the brain damage
  • the length of time they were unconscious

A coma is a prolonged state of unconsciousness that occurs when part of the brain is damaged. It can be caused by a variety of factors, such as trauma to the brain, drug overdose, or unmanaged diabetes.

In many cases, a coma lasts for a few weeks. But, some people may remain in a coma for much longer. Long-term outcomes depend on what caused the coma and the site and extent of damage to the brain.

Some people emerge from a coma with physical, intellectual, or psychological conditions. And some people recover from a coma without any lasting symptoms.

People who remain in a coma for more than a year are unlikely to come out of that state — but that’s not always the case. In more severe coma situations, it can be difficult to assess when someone will wake up.