title: Indirect associations of combat exposure with post-deployment physical symptoms in U.S. soldiers: roles of post-traumatic stress disorder, depression and insomnia.
abstract: OBJECTIVE
  To characterize the indirect associations of combat exposure with post-deployment physical symptoms through shared associations with post-traumatic stress disorder (PTSD), depression and insomnia symptoms.
  
  
  METHODS
  Surveys were administered to a sample of U.S. soldiers (N = 587) three months after a 15-month deployment to Iraq. A multiple indirect effects model was used to characterize direct and indirect associations between combat exposure and physical symptoms.
  
  
  RESULTS
  Despite a zero-order correlation between combat exposure and physical symptoms, the multiple indirect effects analysis did not provide evidence of a direct association between these variables. Evidence for a significant indirect association of combat exposure and physical symptoms was observed through PTSD, depression, and insomnia symptoms. In fact, 92% of the total effect of combat exposure on physical symptoms scores was indirect. These findings were evident even after adjusting for the physical injury and relevant demographics.
  
  
  CONCLUSIONS
  This is the first empirical study to suggest that PTSD, depression and insomnia collectively and independently contribute to the association between combat exposure and post-deployment physical symptoms. Limitations, future research directions, and potential policy implications are discussed.
authors.affiliation: Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, United States. Electronic address: phillip.j.quartana2.civ@mail.mil.
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Quartana
authors.affiliation: Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, United States.
authors.forename: Joshua E
authors.initials: JE
authors.lastname: Wilk
authors.affiliation: Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, United States.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Balkin
authors.affiliation: Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, United States.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Hoge
mesh_terms: D000328:Adult; D003863:Depression / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D006801:Humans; D054542:Iraq War, 2003-2011; D008297:Male; D008889:Military Personnel / Q000523:psychology* / Q000706:statistics & numerical data*; D007319:Sleep Initiation and Maintenance Disorders / Q000453:epidemiology* / Q000209:etiology; D013313:Stress Disorders, Post-Traumatic / Q000453:epidemiology* / Q000209:etiology; D014481:United States / Q000453:epidemiology
keywords: Combat exposure; Depression; Insomnia; Military; PTSD; Pain; Physical symptoms