title: EFFECT OF THE APOE ε4 ALLELE AND COMBAT EXPOSURE ON PTSD AMONG IRAQ/AFGHANISTAN-ERA VETERANS.
abstract: BACKGROUND
  The apolipoprotein E (APOE) ε4 allele has been implicated in a range of neuropsychiatric conditions. The present research examined if the ε4 allele of the APOE gene moderated the effect of combat exposure on posttraumatic stress disorder (PTSD) among Iraq/Afghanistan-era veterans.
  
  
  METHODS
  Participants included 765 non-Hispanic White (NHW) and 859 non-Hispanic Black (NHB) Iraq/Afghanistan-era veterans. A structured interview established psychiatric diagnoses. Combat exposure and PTSD symptom severity were assessed via self-report.
  
  
  RESULTS
  The most common lifetime diagnoses were depression (39.2%), PTSD (38.4%), and alcohol dependence (24.38%). After correcting for multiple comparisons, no significant effects were observed on any of the outcomes among the NHW sample; however, within the NHB sample, significant gene × environment (G × E) interactions were observed for lifetime PTSD (P = .0029) and PTSD symptom severity (P = .0009). In each case, the APOE ε4 allele had no effect on the outcomes when combat exposure was low; however, when combat exposure was high, an additive effect was observed such that ε4 homozygotes exposed to high levels of combat reported the highest rates of PTSD (92%) and the worst symptom severity scores on the Davidson Trauma Scale (M = 79.5).
  
  
  CONCLUSIONS
  Although preliminary, these findings suggest that the APOE ε4 allele, in conjunction with exposure to high levels of combat exposure, may increase veterans' risk for developing PTSD.
authors.affiliation: Durham Veterans Affairs Medical Center, Durham, North Carolina; The VA Mid-Atlantic Mental Illness Research, Education, and Clinical Center, Durham, North Carolina; Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, North Carolina.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Kimbrel
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hauser
authors.forename: Melanie
authors.initials: M
authors.lastname: Garrett
authors.forename: Allison
authors.initials: A
authors.lastname: Ashley-Koch
authors.forename: Yutao
authors.initials: Y
authors.lastname: Liu
authors.forename: Michelle F
authors.initials: MF
authors.lastname: Dennis
authors.forename: Rebecca C
authors.initials: RC
authors.lastname: Klein
authors.forename: Jean C
authors.initials: JC
authors.lastname: Beckham
mesh_terms: D055826:Afghan Campaign 2001-; D001741:Black or African American / Q000235:genetics / Q000523:psychology / Q000706:statistics & numerical data; D000483:Alleles; D053327:Apolipoprotein E4 / Q000235:genetics*; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D054542:Iraq War, 2003-2011; D008297:Male; D057566:Self Report; D013313:Stress Disorders, Post-Traumatic / Q000235:genetics* / Q000523:psychology; D014728:Veterans / Q000523:psychology* / Q000706:statistics & numerical data; D014857:Warfare; D044465:White People / Q000235:genetics / Q000523:psychology / Q000706:statistics & numerical data
chemical_list: D053327:Apolipoprotein E4
keywords: APOE; PTSD; comorbidity; depression; genetic; veteran