What is Chronic Fatigue Syndrome?

Chronic fatigue syndrome isn’t just like being tired. It’s a fatigue that can be so severe that it gets in the way of your normal daily activities.

If you have it, physical activity can leave you tired for a long time. You find it very hard to move around. It can be hard to do even simple things, or to complete daily tasks. Rest and sleep don’t seem to help.

Even mental activity makes you feel very tired, and it’s sometimes hard to concentrate.

Chronic fatigue syndrome is also known as myalgic encephalomyelitis, or systemic exertion intolerance disease. It tends to cycle through flareups and remissions. There isn’t any known cure, but different treatments can help the symptoms.

Facts about Chronic Fatigue Syndrome

  • It affects about 1 million Americans.
  • Anyone can get it, including children and teens.
  • It is most common in women in their 40s and 50s.
  • Women are two to four times more likely to develop it than men.
  • Most cases are mild or moderate.
  • About 1 in 4 people with the condition have severe symptoms.

If you have mild chronic fatigue syndrome, you can probably manage on your own. Moderate symptoms can make it hard for you to move around. For example, you might need to sleep in the afternoons.

If your symptoms are severe, the impact on your quality of life and abilities can be as bad as if you had lupus, heart disease, or rheumatoid arthritis.


How Does It Happen?

Doctors don’t know the cause of chronic fatigue syndrome, but there are theories about things that may contribute to it.

Genes: Sometimes several cases happen in the same family, which could mean there’s a genetic link.

Infections or other illness: Researchers have studied a number of different infections to find out if they could lead to chronic fatigue syndrome:

  • Epstein-Barr Virus (which can cause mononucleosis)
  • Ross River virus
  • Coxsackievirus type B

Serotonin and cortisol: Some people with chronic fatigue syndrome have high levels of serotonin, a brain chemical that helps manage sleep. Others have low levels of cortisol, a hormone that the body releases in response to stress. In fact, some people say that their symptoms started after a period of major stress.

Immune system problems: How your body reacts to illness – whether too strongly or not strongly enough -- could also play a part. But all researchers don’t agree on that.

Blood pressure issues: Very low blood pressure, the type that causes fainting, might also trigger the condition.

How Can I Find Out If I Have It?

You’ll need to see your doctor to find out if you have chronic fatigue syndrome. Remember that it can be hard to diagnose. There’s not a brain scan or blood test to detect it.

Because extreme fatigue is a symptom of so many conditions, your doctor will want to rule out other things first. You’ll need to get a complete checkup and talk with your doctor about all your symptoms.

WebMD Medical Reference Reviewed by Minesh Khatri, MD on August 14, 2018



CDC: “Chronic Fatigue Syndrome.”

WebMD Medical Reference: "Coxsackie Virus."

Office of Women’s Health, U.S. Department of Health and Human Services: “Chronic fatigue syndrome.”

National Health Service (U.K.): “Chronic fatigue syndrome.”

Narita, M. Biochemical and Biophysical Research Communications, November 2003.

Sharpe, M. BMJ, July 1997.

Cleare, A. The American Journal of Psychiatry, April 2001.

Genetics Home Reference: “Corticosteroid-binding globulin deficiency.”

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