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A population-based study of chronic fatigue syndrome (CFS) experienced in differing patient groups: An effort to replicate Vercoulen et al.'s model of CFS

Background: Vercoulen et al.'s (1998) model characterizes patients with chronic fatigue syndrome (CFS) as having insufficient motivation for physical activity or recovery, lacking an internal locus of control, and maintaining a self-defeating preoccupation with symptoms. However, this model has only been tested in a poorly specified group using a single comparison sample. Aims: To investigate whether Vercoulen et al.'s model provides an adequate description of CFS in a community-based sample. Method: A community-based sample recruited through telephone interviewing (N = 28,763) produced five groups (CFS, CF-psychiatrically-explained symptoms, CF-medically-unexplained symptoms, CF-substance misuse, and idiopathic CF). The data were analysed using path analysis with the endogenous (dependent) variables, fatigue severity, physical activity, and impairment, were ratio-level measurements and consisted of at least four values. The exogenous (independent) variables except for causal attribution of fatigue were also ratio-level measurements. Results: The current investigation found that the Vercoulen et al. model adequately represented chronic fatigue secondary to psychiatric conditions but not CFS. Conclusions: This finding points to important differences between CFS and psychiatrically-explained chronic fatigue which may have an impact on the development of therapy as well as explanatory models. Declaration of interest: Financial support for this article was provided by the National Institutes of Allergies and Infectious Diseases grant number AI36295. There are no financial relationships that pose a conflict of interest.