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Chronic fatigue syndrome is a condition of prolonged and severe tiredness or weariness (fatigue) that is not relieved by rest and is not directly caused by other conditions. To be diagnosed with this condition, your tiredness must be severe enough to decrease your ability to participate in ordinary activities by 50%.

See also: Fatigue

Alternative Names:

CFS; Fatigue - chronic; Immune dysfunction syndrome

Causes, incidence, and risk factors:

The exact cause of chronic fatigue syndrome (CFS) is unknown. Some researchers suspect it may be caused by a virus, such as Epstein-Barr virus or human herpes virus-6 (HHV-6). However, no specific virus has been identified as the cause.

Studies suggest that CFS may be caused by inflammation along the nervous system, and that this inflammation may be some sort of immune response or process.

Other factors such as age, prior illness, stress, environment, or genetics may also play a role.

CFS most commonly occurs in women ages 30 to 50.

The Centers for Disease Control (CDC) describes CFS as a distinct disorder with specific symptoms and physical signs, based on ruling out other possible causes. The number of persons with CFS is unknown.


Symptoms of CFS are similar to those of most common viral infections (muscle aches, headache, and fatigue). They come on within a few hours or days and last for 6 months or more.

Main symptoms:

  • Fatigue or tiredness, never experienced to this extent before (new onset), lasting at least 6 months and not relieved by bed rest
  • Fatigue that is severe enough to restrict activity (serious fatigue develops with less than one-half of the exertion compared with before the illness)

Other symptoms:

  • Fatigue lasting more than 24 hours after an amount of exercise that would normally be easily tolerated
  • Feeling unrefreshed after sleeping an adequate amount of time
  • Forgetfulness or other similar symptoms including difficulty concentrating, confusion, or irritability
  • Headaches, different from previous headaches in quality, severity, or pattern
  • Joint pain, often moving from joint to joint (migratory arthralgias), without joint swelling or redness
  • Lymph node tenderness in the neck or armpit
  • Mild fever (101 degrees F or less)
  • Muscle aches (myalgias )
  • Muscle weakness , all over or multiple locations, not explained by any known disorder
  • Sore throat

Signs and tests:

Physical examination may confirm the fever, lymph node tenderness, lymph node swelling, or other symptoms. The throat may appear red without drainage or pus.

The health care provider will diagnose chronic fatigue syndrome (CFS) only after ruling out all other known possible causes of fatigue, such as:

  • Drug dependence
  • Immune or autoimmune disorders
  • Infections
  • Muscle or nerve diseases (such as multiple sclerosis )
  • Endocrine diseases (such as hypothyroidism )
  • Other illnesses (such as heart, kidney, liver diseases)
  • Psychiatric or psychological illnesses, particularly depression (since CFS itself may be associated with depression, a diagnosis of depression does not rule out CFS but fatigue related to depression alone must be ruled out for CFS to be diagnosed)
  • Tumors

A diagnosis of CFS must include:

  • Absence of other causes of chronic fatigue (excluding depression)
  • At least four of the other symptoms listed
  • Extreme, prolonged fatigue

There are no specific tests to confirm the diagnosis of CFS, though a variety of tests are usually done to exclude other possible causes of the symptoms.

The following test results, while not specific enough to diagnose CFS, are seen consistently in people who are eventually diagnosed with the disorder:

  • Brain MRI showing swelling in the brain or destruction of part of the nerve cells (demyelination )
  • Higher levels of specific white blood cells (CD4 T cells) compared with other types of white blood cells (CD8 T cells)
  • Specific white blood cells (lymphocytes) containing active forms of EBV or HHV-6


There is currently no cure for CFS. Instead, the symptoms are treated. Many people with CFS experience depression and other psychological problems that may improve with treatment.

Some of the proposed treatments include:

  • Antiviral drugs (such as acyclovir)
  • Drugs to fight yeast infections (such as nystatin)
  • Medications to reduce pain, discomfort, and fever
  • Medications to treat anxiety (antianxiety drugs)
  • Medications to treat depression (antidepressant drugs)

Some medications can cause adverse reactions or side effects that are worse than the original symptoms of chronic fatigue syndrome.

Patients with CFS are encouraged to maintain active social lives. Mild physical exercise may also be helpful.

Expectations (prognosis):

The long-term outlook for patients with CFS is variable and difficult to predict when symptoms first start. Some patients have been reported to completely recover after 6 months to a year. Others may take longer for a complete recovery.

Some patients report never returning to their pre-illness state. Most studies report that patients treated in an extensive rehabilitation program are more likely to recover completely than those patients who don't seek treatment.

  • Depression (related both to symptoms and lack of diagnosis)
  • Lifestyle restrictions (some people are so fatigued that they are essentially disabled during the course of the illness)
  • Side effects and adverse reactions to medication treatments
  • Social isolation caused by fatigue

Calling your health care provider:

Call for an appointment with your health care provider if you experience persistent, severe fatigue, with or without other symptoms of this disorder. Other more serious disorders can cause similar symptoms and should be ruled out.

See also:Chronic fatigue syndrome - resources


Harris ED, Budd RC, Genovese MC, Firestein GS, Sargent JS, Sledge CB. Kelley's Textbook of Rheumatology. 7th ed. St. Louis, Mo: WB Saunders; 2005:525.

Rakel RE, Bope ET. Conn's Current Therapy 2008. 60th ed. Philadelphia, Pa: Saunders Elsevier; 2008.

Review Date: 2/3/2009
Reviewed By: Mark James Borigini, Associate Clinical Professor of Medicine, University of California, Irvine, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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