title: The comorbidity of self-reported chronic fatigue syndrome, post-traumatic stress disorder, and traumatic symptoms.
abstract: BACKGROUND
  Data from primary care and community samples suggest higher rates of post-traumatic stress disorder (PTSD) among individuals with chronic fatigue syndrome (CFS).
  
  
  OBJECTIVE
  This study investigated the co-occurrence of CFS, PTSD, and trauma symptoms and assessed the contribution of familial factors to the association of CFS with lifetime PTSD and current traumatic symptoms.
  
  
  METHODS
  Data on lifetime CFS and PTSD, as measured by self-report of a doctor's diagnosis of the disorder, and standardized questionnaire data on traumatic symptoms, using the Impact of Events Scale (IES), were obtained from 8544 female and male twins from the community-based University of Washington Twin Registry.
  
  
  RESULTS
  Lifetime prevalence of CFS was 2% and lifetime prevalence of PTSD was 4%. Participants who reported a history of PTSD were over eight times more likely to report a history of CFS. Participants with scores ≥ 26 on the IES were over four times more likely to report CFS than those who had scores ≤ 25. These associations were attenuated but remained significant after adjusting for familial factors through within-twin pair analyses.
  
  
  CONCLUSIONS
  These results support similar findings that a lifetime diagnosis of CFS is strongly associated with both lifetime PTSD and current traumatic symptoms, although familial factors, such as shared genetic and environmental contributions, played a limited role in the relationship between CFS, PTSD, and traumatic symptoms. These findings suggest that future research should investigate both the familial and the unique environmental factors that may give rise to both CFS and PTSD.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA, USA.
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Dansie
authors.forename: Pia
authors.initials: P
authors.lastname: Heppner
authors.forename: Helena
authors.initials: H
authors.lastname: Furberg
authors.forename: Jack
authors.initials: J
authors.lastname: Goldberg
authors.forename: Dedra
authors.initials: D
authors.lastname: Buchwald
authors.forename: Niloofar
authors.initials: N
authors.lastname: Afari
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D003710:Demography; D004200:Diseases in Twins / Q000453:epidemiology*; D004812:Epidemiologic Methods; D015673:Fatigue Syndrome, Chronic / Q000453:epidemiology* / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008016:Life Change Events; D008297:Male; D008875:Middle Aged; D013313:Stress Disorders, Post-Traumatic / Q000453:epidemiology* / Q000235:genetics / Q000523:psychology; D014481:United States / Q000453:epidemiology; D055815:Young Adult