Sleep and neuroimmune function in chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is a medically unexplained condition characterized by persistent or relapsing fatigue for at least 6 months, which substantially interferes with normal activities. It is largely a diagnosis of exclusion. The fatigue is unrelieved by rest and exacerbated by exercise. While depression may be associated with fatigue, chronic fatigue syndrome can occur in the absence of depressive disorders; approximately 60% of patients studied in our research center were negative for depression. The illness affects women twice as often as men (0.52% versus 0.29%) (Jason et al. 1999; Path, Scherbaum, and Bornstein 2000) and is often disabling.