LeardMann et al. BMC Public Health 2010, 10:437 http://www.biomedcentral.com/1471-2458/10/437 CM codes 290, 293-298, 300, 301, 306, 308, 309-312, and 316), excluding disorders specific to childhood, sex- ual deviations, special syndromes, mental retardation, and substance abuse or dependence. Coding was based on the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) [25]. For the purpose of this investigation, responders were classified as having an outcome if one of the ICD-9-CM-coded diagnoses was listed in the medical record within 24 months following deployment and prior to the end of the study period. Diagnoses during deployment often do not appear in electronic medical records, therefore those diagnosed with an outcome during a deployment were only classified as having an event if an additional diag- nosis appeared in the medical record after the individual returned from deployment. The majority of nondeployed Marines are unlikely to experience traumatic events resembling those of their deployed peers. It was not possible to assess which non- deployed Marines experienced traumatic events during the study period. Furthermore, nondeploying Marines may be fundamentally different from their peers since all Marines should be readily deployable; reasons for nondeployment were not possible to discern in this study. As experiencing a traumatic event is a necessary precursor to the development of PTSD, the population for this study included a subset of Marines who com- pleted the RAP survey and were deployed in support of the conflicts in Iraq and Afghanistan between Septem- ber 1, 2001 and June 30, 2004. Of the 9021 eligible responders, those who deployed prior to completing the RAP survey (n = 34), had a diagnosis of PTSD before or during their first deployment (n = 6), or had missing data (n = 590) were excluded from all analyses. When analyzing mental health disorders not specific to PTSD, responders were also excluded if they had a diagnosis for any of the mental health disorders prior to or during their first deployment (n = 167). Because MCRD San Diego does not train female Marines, analysis in this study was limited to men. Statistical analysis Descriptive investigation of population characteristics was completed. Univariate analyses, including chi-square statistics and measures of association, were performed. Cox proportional hazard modeling was used to evaluate associations between ACE and PTSD. The 7 individual ACE categories were assessed together in 1 model, using a dichotomous “yes” or “no” response for each category. The degree of multiple ACE was examined in a separate model, which was categorized as those reporting no ACE, ACE in 1 category, and ACE in 2 or more categories. All multivariable modeling was adjusted for covariates that were significantly associated Page 3 of 8 with the outcome or confounded the relationship between ACE and PTSD, all other variables were removed from the multivariable models. Follow-up time was calculated from the time of first deployment until (1) date of first event, (2) 2 years after the last deploy- ment, (3) date of separation from the military, or (4) the end of the study, June 30, 2005, whichever occurred first. All data analyses were completed using SAS Version 9.1 (SAS Institute, Inc., Cary, NC). This research has been conducted in compliance with all applicable federal regulations governing the protection of human subjects in research (NHRC Protocol 2000.0003). This study was approved by the Institutional Review Board of the Naval Health Research Center. Written consent was obtained from all study participants. Results Of the 9021 RAP responders who were deployed in support of the current conflicts in Iraq and Afghani- stan between September 1, 2001 and June 30, 2004, 8391 (93%) met the study criteria. Demographic char- acteristics of the entire study, and those diagnosed with postdeployment PTSD, are compared in Table 1. A greater proportion of those diagnosed with PTSD were white non-Hispanic, married, non-problematic drinkers, current smokers, deployed more than once, and diagnosed with a non-PTSD mental health disor- der prior to their initial deployment. Additionally, a greater proportion of responders diagnosed with PTSD scored in the lowest quartile for AFQT, reported hav- ing 1 or fewer close friends, and reported poor mental health some, most, or all of the time at the beginning of military training. Adverse childhood experiences of those diagnosed with PTSD were compared with the study sample (Table 2). A greater proportion of those diagnosed with PTSD reported childhood physical neglect, emotional neglect, emotional abuse, and domestic violence. Addi- tionally, a greater proportion of those diagnosed with PTSD also self-reported a history of ACE in more than 1 category than the study sample in general. Those who self-reported being physically neglected as a child were more likely to be diagnosed with postde- ployment PTSD (hazard ratio [HR] = 1.74; 95% confi- dence interval [CI] = 1.17, 2.59), after adjusting for history of ACE in other categories, and other covariates and confounders (Table 3). Furthermore, Marines who were married at the time of deployment, deployed more than once, and reported being diagnosed with a mental health disorder were at greater risk for postdeployment PTSD, while those who scored anywhere above the 25th percentile on the AFQT were at a lower risk for postde- ployment PTSD.