Abstract

Chronic fatigue syndrome (CFS) describes a disorder consisting of chronic debilitating fatigue that cannot be explained by any known chronic medical or psychological condition (Fukuda et al., 1994). While a variety of case definitions exist, often with varying nomenclatures (reviewed in Christley, Duffy, & Martin, 2011), the most widely accepted for research purposes remains the 1994 Centers for Disease Control and Prevention definition (Harvey, Wadsworth, Wessely, & Hotopf, 2008). The core feature of a CFS diagnosis is the exclusion of any active medical condition that may explain the presence of the symptoms (e.g., severe obesity, cancer hypothyroidism, primary sleep disorders, rheumatoid arthritis, multiple sclerosis, Hepatitis B or C, major depressive disorders with psychotic or melancholic features, bipolar affective disorders, schizophrenia, dementia, alcohol abuse; Fukuda et al., 1994). CFS is a disorder affecting approximately 0.5 percent of the population (Jason et al., 1999b).