ABSTRACT
CHRONIC FATIGUE SYNDROME (CFS) and the relatedfibromyalgia (FM) syndrome are largely overlapping disorders, mainly characterized by long-lasting, medically unexplained physical and mental fatigue, effort intolerance and widespread musculoskeletal pain. Consensus diagnostic criteria have been formulated for both syndromes (Fukuda et al., 1994; Wolfe et al., 1990), but the definition and delineation of the syndromes remain controversial (Nimnuan et al., 2001; Reeves et al., 2003; Wessely and White, 2004), and even the very existence of the syndromes has been a matter of debate (Van Houdenhove, 2003).
