Chronic fatigue syndrome (CFS) is a condition of prolonged, severe tiredness or weariness (fatigue) that is not relieved by rest and is not directly caused by other conditions. CFS most often occurs in women ages 30 to 50.

The cause of CFS is not known. Some researchers suspect it may be caused by a virus, but no definite viral cause has been found. An immune response may also be involved.

Major symptoms of CFS are:

• Fatigue or tiredness that has never experienced to this extent before, lasting at least six months and not relieved by bed rest
• Fatigue that is severe enough to restrict normal activities by at least 50 percent

Other symptoms include:

• Fatigue lasting more than 24 hours that develops after exercise that would normally be easily tolerated
• Mild fever
• sore throat, and headaches
• Lymph node tenderness in the neck or armpit
• Muscle aches and muscle weakness, all over or in more than one location
• Sleep disturbances, such as sleeping too much or difficulty falling asleep or remaining asleep
• Joint pain without joint swelling or redness
• Unusual nervous system symptoms, such as increased sensitivity to light, forgetfulness, irritability, and depression

CFS can be diagnosed only after ruling out all other known possible causes of fatigue. No treatment has been proven effective in curing CFS, although lifestyle changes can help and the symptoms are treated with medications. Maintaining active social lives and mild physical exercise may also help people with CFS.

MedStar National Rehabilitation Network experts can help assess the problem and then recommend appropriate lifestyle changes and mild exercises.