title: A twin registry study of the relationship between posttraumatic stress disorder and nicotine dependence in men.
abstract: BACKGROUND
  Recent studies indicate a strong association between posttraumatic stress disorder (PTSD) and nicotine dependence (ND). However, the explanation for the association remains unclear.
  
  
  OBJECTIVE
  To test competing explanations for the association between PTSD and ND.
  
  
  METHODS
  Analysis of data on 6744 members of the Vietnam Era Twin Registry, a national registry of all male-male twin pairs who served in the military during the Vietnam era interviewed in 1991-1992.
  
  
  METHODS
  Risk of PTSD and ND using the Diagnostic Interview Schedule for the DSM-III-R.
  
  
  RESULTS
  The prevalence of ND was elevated among trauma-exposed individuals (52.0%) and those with PTSD (71.7%) compared with unexposed individuals (40.5%). This association was significant for ND and for trauma without PTSD (odds ratio, 1.31; 95% confidence interval [CI], 1.18-1.45) and for PTSD (odds ratio, 2.34; 95% CI, 1.92-2.84) and was not entirely explained by shared risk factors. Shared genetic effects explained 63% of the PTSD-ND association; the remaining covariance was explained by individual-specific environmental effects. Using survival analysis with time-dependent covariates, ND was associated with a substantially increased risk of PTSD among trauma-exposed men (hazard ratio, 1.98; 95% CI, 1.61-2.42). Trauma (hazard ratio, 1.49; 95% CI, 1.35-1.64) and PTSD (hazard ratio, 1.36; 95% CI, 1.14-1.61) were less strongly but significantly associated with increased risk of ND onset after controlling for shared risk factors.
  
  
  CONCLUSIONS
  Most of the PTSD-ND association is explained by shared genetic effects. However, there is a substantial, robust PTSD-ND association not explained by shared risk factors. Multiple explanations for the association were supported; however, the strongest association was consistent with preexisting ND increasing the risk of PTSD onset. These data suggest that male veterans with a history of ND may be at increased risk for PTSD. Further research on the biological mechanisms underlying PTSD-ND comorbidity is needed.
authors.affiliation: Department of Society, Human Development, and Health, Harvard School of Public Health, 677 Huntington Avenue, Kresge 613, Boston, MA 02115, USA. kkoenen@hsph.harvard.edu
authors.forename: Karestan C
authors.initials: KC
authors.lastname: Koenen
authors.forename: Brian
authors.initials: B
authors.lastname: Hitsman
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lyons
authors.forename: Raymond
authors.initials: R
authors.lastname: Niaura
authors.forename: Jeanne
authors.initials: J
authors.lastname: McCaffery
authors.forename: Jack
authors.initials: J
authors.lastname: Goldberg
authors.forename: Seth A
authors.initials: SA
authors.lastname: Eisen
authors.forename: William
authors.initials: W
authors.lastname: True
authors.forename: Ming
authors.initials: M
authors.lastname: Tsuang
mesh_terms: D000328:Adult; D003130:Combat Disorders / Q000453:epidemiology / Q000523:psychology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004200:Diseases in Twins / Q000453:epidemiology* / Q000523:psychology; D006801:Humans; D008016:Life Change Events; D008297:Male; D008875:Middle Aged; D008889:Military Personnel / Q000706:statistics & numerical data; D015995:Prevalence; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D012042:Registries; D012737:Sex Factors; D013313:Stress Disorders, Post-Traumatic / Q000453:epidemiology* / Q000523:psychology; D016019:Survival Analysis; D014029:Tobacco Use Disorder / Q000453:epidemiology* / Q000523:psychology; D014481:United States; D014728:Veterans; D047829:Vietnam Conflict