What is a coma?

A coma is when someone is in a coma for an extended period of time. Their eyes are closed, and they do not respond to sounds or other things in their environment. They cannot be awakened even by severe or painful stimulation.

Coma is different from sleep. In a coma, the brain does not go through its normal sleep cycle. A sleeping person may move if uncomfortable, but a comatose person will not.

In this article, you’ll learn what causes a coma, what it takes to recover from a coma, and some similar states of unconsciousness.

What causes a coma?

Many types of illnesses and injuries can damage your brain cells and put you in a coma, including:

  • serious head injury
  • Seizures
  • brain infection
  • Brain damage due to hypoxia
  • drug overdose
  • stroke
  • A chemical imbalance caused by a disease, such as low blood sugar (hypoglycemia) in diabetes

Most comas only last a few weeks, although they can last longer — even years. Much depends on what caused the coma in the first place.

If enough nerve cells die in areas of the brain that are critical to staying awake, the person may never regain normal consciousness. These areas include:

  • The thalamus: This area is located low in the back of your head, and it plays a role in movement, processing information from your senses, sleep, and alertness.
  • Brainstem: Just below the thalamus, the brainstem connects your brain and spinal cord. It plays a role in breathing, heart rate, balance, coordination and reflexes.
  • Most of the cerebral cortex: the outer layer of gray matter on the brain. It forms connections between brain regions and is involved in a large number of functions.

nerve cells were able regenerate, but they only do so in specific parts of the brain. Plus, if it does happen, it’s a very slow process.

However, technically there are other reasons why someone is in a coma.

Every time general anesthesia is used, the doctor puts the patient in a coma. However, most people wake up a few hours after the body processes the medication.

The definition also includes people who are rendered unconscious by drugs, toxins, or infections. As with anesthesia, they usually wake up when the body is free of whatever is causing unconsciousness.

Understanding Traumatic Brain Injury

what happens during a coma

During a coma, there is very little brain activity. Most of the body continues to function because it can repair itself and get out of this state. However, there is no awareness.

A comatose person may move in a waking manner, which may mislead friends and family. For example, they may make faces if something causes pain.

They may even look away from pain. In so-called Lazarus syndrome, a particularly strong reflex causes a comatose person to sit up straight.

However, these responses are just reflexes. This is similar to what happens to your leg when a health care provider hits your knee with a hammer. These movements do not mean that someone is awake, conscious, or improving. These are just automatic movements.

recovering from coma

Whether a person can recover from a coma depends on many factors, including what put them in the coma in the first place.

For example, coma from traumatic brain injury tends to have a better prognosis than coma from cardiac arrest.

Younger patients tend to do better than older patients. A person in a drug-induced coma may wake up naturally when the drug is cleared from their system.

But people with permanent brain damage can develop a persistent vegetative state in which they appear awake but unresponsive. It can also lead to brain death.

In general, the longer a person remains in a coma, the less likely they are to regain alertness. But the only way to know for sure if someone will recover from a coma is to wait a reasonable amount of time before watching.

How long to wait can be a tough decision. It depends on the unique circumstances of the individual and their loved ones. The patient’s medical team can provide helpful information to guide next steps.


A coma is a state that involves unconsciousness, closed eyes, and inability to be awakened. Some causes include head injury, seizures, brain damage or infection, stroke, drug overdose, or very low blood sugar. If the damage to certain brain areas is severe enough, the person is less likely to wake up from a coma.

other unconscious states

The same injuries and illnesses that put people in a coma can also lead to other states of unconsciousness. The four different states, from least to most severe, are:

  • minimal awareness
  • coma
  • vegetative state
  • brain death

Someone in the first three states may transition between them. For example, they may go from a coma to minimal consciousness. This may indicate recovery, but it doesn’t always mean they will wake up.

If their body cannot repair the damage, someone may go from a coma or a vegetative state to brain death.

minimal awareness

Minimal consciousness is a less serious state than coma. Doctors usually want signs that someone is minimally conscious, not in a true coma or a vegetative state.

Lightly conscious people are largely unaware of what is going on around them. However, they have enough brain activity to have some reserved awareness of themselves or their surroundings.

This could mean:

  • The ability to consistently follow simple commands
  • Appropriate yes/no answers
  • Demonstrate purposeful behavior (smiling or crying appropriately, adjusting hands to the size and shape of the object being held)

Someone may transition to a minimally conscious state or recover from it. It is also possible for someone to remain minimally conscious indefinitely.

In general, people in a minimally conscious state have better outcomes than those in a persistent coma. Even so, many people who recover from this condition remain severely disabled.

vegetative state

Comatose patients appear to be sleeping, while those in a vegetative state revert to a degree of rude arousal that causes the eyes to open.

The eyes may even move reflexively, as if staring at something in the room. These individuals, however, show no real awareness of themselves or their surroundings. Decreased brain activity in areas that control consciousness.

If the brainstem is intact, the heart, lungs and gastrointestinal tract will continue to function. If not, machines may be required to maintain these functions.

If this condition persists for several months, it is considered a persistent vegetative state (PVS).

This can be permanent. With continued medical care, someone may survive in a persistent vegetative state for decades.

brain death

Brain death means that the person is dead. This happens when brain function stops throughout the brain, including the brain stem. At this point, the person can no longer breathe on his own. If mechanical support is removed, they usually go into cardiac arrest.

There are no documented cases of meaningful recovery among people who have been accurately diagnosed as brain dead. Resurrecting them was considered impossible.

While a qualified doctor can make a diagnosis of brain death based on a physical exam alone, some families prefer additional testing given the severity of the diagnosis.

However, if the bedside examination can be done with complete accuracy, it is unlikely that additional testing will reveal any new or more promising information. Since the brain has been deprived of blood and oxygen, autopsies usually show that much of the brain has been depleted.


The less aware may be able to answer questions and follow simple instructions.

A person in a vegetative state may appear to be more conscious than someone in a coma, but this is not the case. Brain death occurs when a comatose person dies without mechanical support.


A coma is a state of unconsciousness that cannot be awakened. The brain doesn’t go through a normal sleep cycle, and you can’t respond to pain. A coma is caused by brain damage from a head injury or illness.

If damage occurs in certain key areas of the brain, it may not be able to recover. Age and causes of coma are other factors that affect recovery. The longer it lasts, the less likely recovery is.

Other unconscious states also exist. The least conscious individuals retain some awareness and responsiveness. On the other end of the scale is brain death, which means that there is no more activity in the brain and the person is dead.

VigorTip words

If someone you care about is unconscious, ask their healthcare team what state they are in and what kind of awareness they may have.

Understanding the different possible states may affect your behavior around the unconscious and help guide your decisions about their care.

level of medical awareness