Do adverse childhood experiences increase the risk of postdeployment posttraumatic stress disorder in US Marines?

As of March 2010, over 130,000 recruits had completed a RAP survey during initial training, with a response rate over 95%. Development of the RAP survey was a collaborative effort of public health officials, clinicians, and researchers from the Department of Defense, Veterans Health Administration, and Department of Health and Human Services. The survey instrument includes questions on demographics, health, family history, tobacco and alcohol use, mental health history, and ACE [19].

Adverse childhood experience questions on the RAP survey were derived from the Adverse Childhood Experiences Study [20, 21], which adapted questions from the Childhood Trauma Questionnaire [22], Conflict Tactics Scales [23], and sexual abuse questions from Wyatt [24]. Using questions framed to reflect experiences prior to age 17 years, 7 ACE categories were assessed in the current study: (1) physical neglect (lack of care and protection), (2) emotional neglect (lack of feeling loved), (3) physical abuse (pushed, grabbed, shoved, or slapped), (4) emotional abuse (was sworn at, insulted, or put down), (5) sexual abuse, (6) domestic violence, and (7) family history of mental illness or alcohol abuse. Each ACE category was based on 1 self-reported question from the RAP survey, with the exception of family history of mental illness and alcohol abuse, which was assessed using 2 questions. The 7 ACE categories were evaluated as dichotomous "yes" or "no" responses. Questions with a 5-point scale were dichotomized based on criteria used by Dube et al. [21]; for neglect, a positive response was classified if responders reported neglect "often" or more frequently. A 3-level categorical variable was created to evaluate overall occurrences of childhood adversity: no history of ACE, history of ACE in 1 category, or history of ACE in 2 or more categories.

Other questions from the RAP survey were used as covariates in multivariable modeling, including education, parental education, number of close friends, alcohol-drinking behavior, smoking status, self-reported mental health status, visiting a mental health professional in the 5 years prior to survey completion, and prior traumatic event (including being in a severe accident, seeing someone badly injured or killed, being attacked or assaulted, threatened with a weapon, or being raped).

Deployment data, obtained from the Defense Manpower Data Center (DMDC), include all service members deployed in support of the conflicts in Iraq and Afghanistan since September 2001. Length of deployment was defined as the cumulative number of days deployed after completion of the RAP survey until first mental health event, 2 years after last deployment, or June 30, 2005, whichever came first. Marital status, age at first deployment, Armed Forces Qualification Test (AFQT) score, and race/ethnicity were also acquired from DMDC. The AFQT score is computed using four tests that measure knowledge in high school level subjects.

Patient medical records were used to determine diagnosis for PTSD, and mental health disorders that may be manifestations of PTSD. Hospitalization and outpatient data sources, including all visits to military treatment facilities as well as civilian visits billed to the military, were used in these analyses. All diagnostic fields were scanned for PTSD (ICD-9-CM codes 308 and 309.8) and other mental health disorders (ICD-9-CM codes 290, 293-298, 300, 301, 306, 308, 309-312, and 316), excluding disorders specific to childhood, sexual 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 diagnosis 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 nondeployed 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 completed the RAP survey and were deployed in support of the conflicts in Iraq and Afghanistan between September 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.

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 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 deployment, (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.

This study has some limitations that should be considered. A study period of only 2 years may not be long enough to adequately capture all members who may be diagnosed with PTSD; although the onset of PTSD symptoms usually occurs within 3 months after a traumatic event [40]. Previous studies have identified combat exposures as one of the most consistent risk factors for developing combat-related PTSD [5, 7, 10, 41]. While cumulative length of deployment was used as a covariate in this study, actual combat exposures could not be assessed in this study. These Marines may have been exposed to varying levels of combat or trauma, however, it is likely that the combat exposure experienced by this homogeneous sample of active duty, male Marines in this study was similar since they all deployed for the first time shortly after finishing recruit training [10]. Responders who had a previous PTSD diagnosis recorded in their military medical records or billed to the military were excluded, though it was not possible to account for PTSD diagnoses that may have occurred before responders joined the Marine Corps. Adverse childhood experiences were self-reported on a survey that was administered at the beginning of recruit training. Like all self-reported data, it is difficult to know the extent of recall bias and reporting bias, especially with a sensitive topic such as ACE. With the low prevalence of PTSD and the sample size of this study, there was insufficient power to detect small differences in the risk of being diagnosed with PTSD across exposure categories. We were able to identify significant differences in risk for more common exposures, such as physical neglect. Since this study was conducted among male Marines, the results may not be generalizable across all service branches or to female personnel.

Despite these limitations, this study had a number of strengths. Prospective design eliminated biases related to same-time assessment of exposures and outcomes. Medical records, an objective outcome measure, were used to assess PTSD in contrast to self-reported symptoms. The electronic medical records are very complete for active-duty service members since medical visits at Department of Defense facilities and those billed to the military are included in these records. Both hospitalization and outpatient data were used to assess PTSD diagnoses, allowing for the full spectrum of health effects to be examined. The all-male population provided unique perspective on ACE, which is not always well described among men. Proportional hazard modeling allowed for hazard risk estimation while adjusting for many covariates and varied length of follow-up.