title: The relationship of fatigue to mental and physical health in a community sample.
abstract: BACKGROUND
  Previous studies have shown fatigue and depression/anxiety to be highly associated with each other. The present study seeks to differentiate between fatigue and depression/anxiety and to investigate the familiality/heritability of fatigue using sib-pairs.
  
  
  METHODS
  The GENESiS study is a questionnaire study based in the United Kingdom that includes a five-item fatigue scale and four mental health measures (GHQ-12, EPQ-N, MASQ-AA, MASQ-HPA). Fatigue data from 10,444 sibling pairs were analysed using multivariate methods and model fitting techniques to investigate the familiality/heritability of fatigue and its relationship with the other mental health measures and physical health items.
  
  
  RESULTS
  Fatigue correlated highly with GHQ-12 (r=0.62, p<0.001). A principal components analysis of the fatigue scale and the GHQ-12 revealed one main component which correlated highly with mental health items, and a smaller second component which correlated modestly with physical health items. Fatigue showed a modest sibling correlation (0.09, p<0.001), and multivariate modelling revealed evidence for familial effects on fatigue that were independent of the mental health measures.
  
  
  CONCLUSIONS
  Fatigue showed a strong relationship with both physical illness and mental health measures. Fatigue is modestly familial and at least part of this familial factor is not shared with mental health measures.
authors.affiliation: Social, Genetic, Developmental Psychiatry Research, Institute of Psychiatry, PO80, 16 De Crespigny Park, Denmark Hill London SE5 8AF, UK. spjgriw@iop.kcl.ac.uk
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Williamson
authors.forename: Shaun
authors.initials: S
authors.lastname: Purcell
authors.forename: Abram
authors.initials: A
authors.lastname: Sterne
authors.forename: Simon
authors.initials: S
authors.lastname: Wessely
authors.forename: Matthew
authors.initials: M
authors.lastname: Hotopf
authors.forename: Anne
authors.initials: A
authors.lastname: Farmer
authors.forename: Pak C
authors.initials: PC
authors.lastname: Sham
mesh_terms: D000328:Adult; D001007:Anxiety / Q000175:diagnosis / Q000453:epidemiology*; D003863:Depression / Q000175:diagnosis / Q000453:epidemiology*; D005221:Fatigue / Q000453:epidemiology* / Q000523:psychology*; D005260:Female; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D012737:Sex Factors; D011795:Surveys and Questionnaires