Chronic fatigue syndrome refers to long-standing severe and disabling fatigue without a proven physical or psychologic cause.
Chronic fatigue syndrome may occur in up to 38 of 100,000 people in the United States. However, a recent telephone survey found the prevalence to be many times higher. Chronic fatigue syndrome affects people primarily between the ages of 20 and 50 and is about 1½ times more common among women than men.
Despite considerable research, the cause of chronic fatigue syndrome remains unknown. Controversy exists as to whether there is a single cause or many causes and whether the cause is physical or psychologic.
Some studies have suggested infection with the Epstein-Barr virus, rubella virus, herpesvirus, or human immunodeficiency virus (HIV) as a possible cause of chronic fatigue syndrome. However, current research indicates that these viral infections probably do not cause this syndrome. It is unclear whether other infections are related to the syndrome.
Some evidence suggests abnormalities of the immune system as possible causes. Other suggested causes include allergies (about 65% of people with chronic fatigue syndrome report previous allergies), hormonal abnormalities, decreased blood flow to the brain, and lack of certain nutrients in the diet.
Chronic fatigue syndrome seems to run in families, possibly supporting an infectious agent as a cause. Alternatively, members of the same family may respond similarly to physical and psychosocial stress.
Some researchers have suggested that prolonged bed rest during convalescence from an illness may play a role in causing this disorder.
Some researchers believe the syndrome ultimately will prove to have several causes, including genetic predisposition and exposure to microbes, toxins, and other physical and emotional factors.
Symptoms and Diagnosis
The main symptom is fatigue that usually lasts at least 6 months and that is severe enough to interfere with daily activities. Severe fatigue is present even on awakening and persists throughout the day. The fatigue often worsens with physical exertion or psychologic stress. However, evidence of muscle weakness or of joint or nerve abnormalities is rare. Symptoms may begin after a coldlike illness that involves tender or painful swollen lymph nodes. In these people, extreme fatigue may begin with a fever and runny nose. However, in many people, fatigue begins without any preceding coldlike illness. Other symptoms that may occur are difficulty concentrating and sleeping, sore throat, headache, joint pains, muscle pains, and abdominal pain.
No laboratory tests are available to confirm a diagnosis of chronic fatigue syndrome. Doctors therefore must rule out other diseases that may cause similar symptoms, such as thyroid disease, psychologic problems, alcoholism, or the early stage of a liver, inflammatory, or kidney disorder. The diagnosis of chronic fatigue syndrome is made only if no other cause, including side effects of drugs, is found to explain the fatigue.
In most cases, symptoms of chronic fatigue syndrome lessen over time.
Excessive periods of prolonged rest cause deconditioning and may worsen symptoms of chronic fatigue syndrome. Gradual introduction of regular aerobic exercise, such as walking, swimming, cycling, or jogging, under close medical supervision may reduce fatigue and improve physical function. Formal, structured physical rehabilitation programs may be best. Psychotherapy, including individual and group behavior therapy, may be helpful as well.
Many different drugs and alternative therapies have been tried. Although many treatments, such as antidepressants and corticosteroids, seem to make a few people feel better, none are clearly effective for all. It is hard for people and doctors to tell what treatments work because symptoms are different in different people and because symptoms may come and go on their own.
Controlled clinical trials are the best way to test therapies, and no drug therapy has been shown to be effective in controlled trials. A number of treatments directed at possible causes, including use of interferons, intravenous injections of immune globulin, and antiviral drugs, have been mostly disappointing. Dietary supplements, such as evening primrose oil, fish oil supplements, and high-dose vitamins, are commonly used, but their benefits remain unproved. Other alternative treatments (for example, essential fatty acids, animal liver extracts, exclusion diets, and removal of dental fillings) have also been ineffective.
Last full review/revision December 2008 by Margaret-Mary G. Wilson, MD