Conditions InDepth: Chronic Fatigue Syndrome (CFS)

Chronic fatigue syndrome (CFS) is a chronic, debilitating disorder that affects your brain and multiple parts of your body. It causes extreme fatigue and is not relieved by bed rest. Physical or mental fatigue often makes the condition worse. Symptoms last at least six months and are severe enough to interfere with daily activities.

There is no specific laboratory test or clinical sign for CFS; therefore, no one knows how many people are affected by this illness. The Centers for Disease Control and Prevention estimates, however, that as many as 500,000 people in the United States have a CFS-like condition.

No one knows what causes CFS. For more than a century, doctors have reported seeing illnesses similar to it. In the 1860s, Dr. George Beard named the syndrome "neurasthenia" because he thought it was a nervous disorder with weakness and fatigue. Subsequent experiments in man supported his idea that the brain is somehow involved in CFS.

In the early 1980s, CFS was stereotyped as a new "yuppie flu," because people who sought help for their symptoms were primarily upper middle-class women in their thirties and forties. Since then, health experts have suggested other explanations for this baffling illness, including various viruses (such as, Epstein-Barr virus, enteroviruses, parvovirus B19, Coxiella burnetii, Chlamydia pneumoniae), malfunction of the hypothalamic-pituitary-adrenal axis, emotional stress, iron-poor blood ( anemia ), low blood sugar ( hypoglycemia ), low blood pressure, environmental allergy or toxins, or a body-wide yeast infection ( candidiasis ). Doctors now report seeing the syndrome in people of all ages, races, and social and economic classes from several countries around the world. The incidence remains a ratio of about 4:1, women to men.

Recovery time varies among individuals with CFS. You may recover to the point where you can resume work and other activities, but continue to experience various or periodic CFS symptoms. CFS typically follows a cyclical course, alternating between periods of illness and relative well-being. You may also recover completely with time.

What are the risk factors for chronic fatigue syndrome?
What are the symptoms of chronic fatigue syndrome?
How is chronic fatigue syndrome diagnosed?
What are the treatments for chronic fatigue syndrome?
Are there screening tests for chronic fatigue syndrome?
How can I reduce my risk of chronic fatigue syndrome?
What questions should I ask my healthcare provider?
What is it like to live with chronic fatigue syndrome?
Where can I get more information about chronic fatigue syndrome?


Centers for Disease Control and Prevention website. Available at: .

Devanur LD, Kerr JR. Chronic fatigue syndrome. J Clin Virol. 2006;37:139-150.

Prins JB, van der Meer JW, Bleijenberg G. Chronic fatigue syndrome. Lancet. 2006;367:346-355.

National Institute of Allergy and Infectious Diseases website. Available at: .

Last reviewed April 2007 by David Juan, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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