Article

A twin study of chronic fatigue

Department of Medicine, University of Washington, Seattle, WA, USA.
Psychosomatic Medicine (Impact Factor: 4.09). 01/2001; 63:936-943. DOI: 10.1097/00006842-200111000-00012
Source: PubMed

ABSTRACT OBJECTIVE: The etiology of chronic fatigue syndrome is unknown, but genetic influences may be important in its expression. Our objective was to assess the role of genetic and environmental factors in unexplained chronic fatigue. METHODS: A classic twin study was conducted using 146 female-female twin pairs, of whom at least one member reported > or =6 months of fatigue. After completing questionnaires on symptoms, zygosity, physical health, and a psychiatric interview, twins were classified using three increasingly stringent definitions: 1) chronic fatigue for > or =6 months, 2) chronic fatigue not explained by exclusionary medical conditions, and 3) idiopathic chronic fatigue not explained by medical or psychiatric exclusionary criteria of the chronic fatigue syndrome case definition. Concordance rates in monozygotic and dizygotic twins were calculated for each fatigue definition along with estimates of the relative magnitude of genetic and environmental influences on chronic fatigue. RESULTS: The concordance rate was higher in monozygotic than dizygotic twins for each definition of chronic fatigue. For idiopathic chronic fatigue, the concordance rates were 55% in monozygotic and 19% in dizygotic twins (p =.042). The estimated heritability in liability was 19% (95% confidence interval = 0-56) for chronic fatigue > or =6 months, 30% (95% confidence interval = 0-81) for chronic fatigue not explained by medical conditions, and 51% (95% confidence interval = 7-96) for idiopathic chronic fatigue. CONCLUSIONS: These results provide evidence supporting the familial aggregation of fatigue and suggest that genes may play a role in the etiology of chronic fatigue syndrome.

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    • "CFS may have a familial predisposition as relatives of patients with CFS may not necessarily meet the criteria for CFS but may be more prone to experience some of the symptoms of CFS (Walsh et al., 2001). Although twin studies allude to the existence of a genetic predisposition to CFS, this may be higher among monozygotic twins compared to dizygotic twins (Buchwald et al., 2001). Twins with CFS may share similar symptoms and experience the same level of severity in CFS related symptoms (Claypoole et al., 2007). "
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    • "Subjects were classified based on the 1994 Centers for Disease Control and Prevention (CDC) CFS case definition (Fukuda, et al., 1994). This cohort has been extensively evaluated in a number of studies regarding the biology of CFS (Aaron, et al., 2002; Aaron, et al., 2001; Armitage, et al., 2009; Ball, et al., 2004; Buchwald, et al., 2001; K. Claypoole, et al., 2001; K. H. Claypoole, et al., 2007; Herrell, et al., 2002; Lewis, et al., 2001; Mahurin, et al., 2004; Poole, Herrell, Ashton, Goldberg, & Buchwald, 2000; Roy-Byrne, et al., 2002; Watson, Jacobsen, Goldberg, Kapur, & Buchwald, 2004; Watson, et al., 2003), and our group has previously reported on immune parameters associated with CFS (Koelle, et al., 2002; Sabath, et al., 2002). From the original samples obtained in 2001 as described in (Koelle, et al., 2002; Sabath, et al., 2002), material was available for this study from 21 same-sex twin pairs (19 female, 2 male). "
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    • "Familial aggregation of FM has been repeatedly demonstrated [2] [3] [4], and a twin study of CWP estimated heritability to be approximately 50% [5]. Twin studies have also reported a genetic component to CFS [6] [7] and IBS [8] [9]. Not all twin studies of IBS, however, have reported a genetic component [10] [11], and others have found that the observed genetic component is explained by a genetic influence on associated psychiatric disorder or a tendency to report multiple bodily symptoms [12] [13]. "
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