Scientists don't know exactly what causes chronic fatigue syndrome. It may be a combination of factors that affect people who were born with a predisposition for the disorder. Some of the factors that have been studied include:

  • Viral infections. Because some people develop chronic fatigue syndrome after having a viral infection, researchers have wondered if some viruses might trigger the disorder. Suspicious viruses have included Epstein-Barr, human herpesvirus 6 and mouse leukemia viruses. No conclusive link has yet been found.
  • Immune system problems. The immune systems of people who have chronic fatigue syndrome appear to be impaired slightly, but it's unclear if this impairment is enough to actually cause the disorder.
  • Hormonal imbalances. People who have chronic fatigue syndrome also sometimes experience abnormal blood levels of hormones produced in the hypothalamus, pituitary gland or adrenal glands. But the significance of these abnormalities is still unknown.
Jun. 18, 2011