Authored by Revere Health

What Causes a Coma?

November 15, 2016 | Neurology

Stroke Prevention and Brain Health

Defined as any extended period of unconsciousness, people in a coma cannot be awoken or stimulated despite the appearance of sleep. The longer a person is in a coma, the larger their overall health and brain risks are. Death or loss of brain function are the most extreme outcomes. There are several types of comas the human body can enter, ranging from generally reversible to permanent and life-altering. Treatments and prognoses vary in similar ways, and are approached on a case-by-case basis. A wide variety of events or disorders can cause a coma, and generally involve some kind of injury to the brain. Here are some of the most common risk factors:

Head Trauma

Significant head injuries cause bleeding or swelling within the brain, which causes brain fluid to press up against the skull. If this pressure becomes too large, the brain itself will begin pushing down on its own brain stem, eventually damaging what’s called the Reticular Activating System (RAS)—the part of the brain in charge of keeping us awake and perceptive.

Because it’s such a broad category, head trauma can also be an underlying precursor for several other distinct causes of comas.

Swelling and Bleeding

These are common results of head trauma, but both conditions can occur in the brain independently. The brain can swell due to circumstances like a hormone or electrolyte imbalance, or from lack of oxygen.

A variety of factors can cause bleeding in the brain, ranging from high blood pressure to tumors or aneurysms in the brain. In both cases, the brain can respond similarly to a head trauma and damage the RAS and brain stem, causing a coma.

Blood Sugar and Diabetes

In extreme cases of diabetes, blood sugar will rise too high or fall too low, processes which can lead to a coma. In most cases, these types of comas can be reversed so long as medical attention is sought in a timely fashion.


People who abuse drugs or alcohol can overdose on these substances, often resulting in a coma for an undefined period of time.


A stroke takes place any time blood flow to the brain is limited or stopped altogether, and coma is a common symptom for those who survive.

Lack of Oxygen

The brain can be deprived of oxygen during specific events or as part of a larger condition. Survivors of any event where airflow is cut off to the entire body – near-drowning, choking or restricted airways – can enter a coma when the brain isn’t receiving enough oxygen.

In addition to restricting blood flow, heart attacks also cut off blood flow to the brain, a process called hypoxia or anoxia. Those who survive heart attacks frequently enter a coma following the cardiac arrest.

Chronic Seizures

Referred to in the medical community as “status epilepticus,” chronic seizures limit the brain’s ability to recover from a traumatic event. If the seizures are frequent enough, this can cause a prolonged coma. Singular incidents of seizure almost never lead directly to a coma, though it’s possible.

Toxic Substances

Toxic substances in large enough doses can cause comas, and these substances can come from either outside or inside the body.  Toxins present in the environment can occasionally lead to comas in some people, and many would consider drugs and alcohol among such toxins.

Toxins in the body involve complications with the body’s ability to process and eliminate certain toxins naturally found inside it, a common disorder following certain major health events. These issues can often be signs of non-coma-related conditions which require immediate attention, but they sometimes result in a coma if toxic levels grow too high.


Certain types of infections in the central nervous system lead to swelling in the brain, and can cause comas through the same process as head traumas.

Revere Health Neurology specialists treat patients with a variety of neurological disorders.





The Live Better Team

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This information is not intended to replace the advice of a medical professional. You should always consult your doctor before making decisions about your health.