Overview

Definition

Chronic fatigue syndrome (CFS), also called Chronic Fatigue and Immune Dysfunction Syndrome (CFIDS) is not simply one or a few episodes of daytime sleepiness. Rather, CFS is a complex, debilitating illness consisting of a severe, persistent lack of energy, generalized muscle or joint aches and difficulty concentrating. The profound fatigue of CFS does not improve after a good night's sleep and worsens with physical or mental exertion.

There are many underlying conditions that cause fatigue, including common viral illnesses, diabetes and anemia. Wakefulness and energy return once the "24-hour flu" runs its course, or medications normalize the blood sugar or blood count. Unlike these conditions, CFS has no clear cause. CFS is not a psychiatric disorder, nor is there a clear metabolic or physical explanation. Furthermore, there is no known test or measurable indicator associated with CFS.

CFS usually comes on suddenly, often following an illness or period of emotional stress. For others CFS comes on gradually without any prior illness or event. The Centers for Disease Control and Prevention (CDC) estimates that CFS affects more than one million people in the United States. There are tens of millions of people with similar fatiguing illnesses who do not fully meet the strict research definition of CFS. Out of a concern that CFS was an infectious disease, the CDC conducted a study from 1989 to 1993 in four cities. In addition to revealing that CFS affects mostly white women in their 30s, no clear evidence for an infectious cause was found.

There is no cure for CFS. However, there are treatments, including a variety of medications, that alleviate symptoms. Given the number of people with CFS and our current gap in knowledge, there are many unfounded claims for treatments or cures. The CDC cautions all to be wary of information "that points to sure cures or that alludes to pathological damage as a consequence of CFS."

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This article was reviewed and updated June 2007.