Chronic Fatigue Syndrome - Causes

There is no single known cause for chronic fatigue syndrome. Some factors that are thought to be responsible for the disease are:

• Viral infections
• Chemical toxins (poisons)
• Allergies
• Abnormalities in the immune system
• Psychological disorders

Many doctors now believe that CFS is not one illness, but a combination of symptoms caused by several factors. According to one theory, the first step in chronic fatigue syndrome is infection by a virus. About 90 percent of all people have a virus in the herpes family in their bodies. Herpes viruses (see herpes infections entry) cause a number of problems, including cold sores and a painful inflammation of the nerves called shingles (see chickenpox entry).

These viruses are usually dormant (not active) in the body. The viruses can become active again, however, if the body is disturbed in some way. Certain chemicals in the air, for example, can cause the viruses to become active and begin to grow. When that happens, the body's immune system starts to fight off the viral infection. It produces chemicals designed to kill the virus. But these chemicals can cause other effects, too. Those effects are similar to ones observed in people with CFS.

The role of psychological factors in CFS is very controversial. Some think that people who are depressed are more likely to develop CFS. A person's mental state, they believe, may influence the way his or her body works. For example, depression (see depressive disorders entry) might cause dormant viruses to become active again. Other experts disagree with this analysis. They say a person's mental state is more likely to be caused by the disease, rather than being a cause of the disease.