The Association Between Combat Exposure and ...

ORIGINAL ARTICLE

The Association Between Combat Exposure and Negative Behavioral and Psychiatric Conditions Michael Shayne Gallaway, PhD, MPH,* David S. Fink, MPH,* Amy M. Millikan, MD, MPH,* Mary M. Mitchell, PhD,* and Michael R. Bell, MD, MPHÞ Abstract: This study evaluated the association between cumulative combat exposures and negative behavioral and psychiatric conditions. A total of 6128 active-duty soldiers completed a survey approximately 6 months after their unit’s most recent combat deployment. The soldiers self-reported combat exposures and behavioral and psychiatric conditions. Multivariable logistic regression was used to assess the association between cumulative combat exposures and behavioral and psychiatric outcomes. In comparison with the referent group of soldiers not previously deployed, the soldiers categorized as having the highest cumulative combat exposures were significantly associated with self-reporting a history of behavioral and psychiatric diagnoses, problematic alcohol misuse, aggression, criminal behavior, and physical altercations with a significant other. The magnitude and the consistency of the association among the soldiers with the highest number of combat exposures suggest that the number of cumulative combat deployment exposures is an important consideration for identifying and treating high-risk soldiers and units returning from combat. Key Words: Deployment, combat exposure, behavioral health, military. (J Nerv Ment Dis 2013;201: 572Y578)

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xisting literature links military combat exposure to negative behavioral and psychiatric outcomes including depression, anxiety, aggression, antisocial behavior, and problematic alcohol use (BoothKewley et al., 2010; Bryan et al., 2010; Hoge et al., 2004; Killgore et al., 2008; Pietrzak et al., 2011; Prigerson et al., 2002; Smith et al., 2008; Wilk et al., 2010). Studies have also examined the impact of multiple deployments on negative behavioral and psychiatric conditions (Hoge et al., 2004; Killgore et al., 2008; Pietrzak et al., 2011). Intensity of combat may be more strongly linked to negative behaviors and psychiatric conditions than is frequency of combat (Hoge et al., 2004; Kang et al., 2003), but this association has not been as well studied (Pietrzak et al., 2011). This study aims to expand on current knowledge by estimating the effect of combined combat exposures and multiple deployments on a range of specific behaviors and psychiatric conditions in a large population of Operation Enduring Freedom/ Operation Iraqi Freedom (OEF/OIF) soldiers.

*Behavioral and Social Health Outcomes Program (BSHOP), US Army Institute of Public Health, US Army Public Health Command, Aberdeen Proving Ground, MD; and †Uniformed Services University of Health Sciences, Bethesda, MD. Send reprint requests to M. Shayne Gallaway, PhD, MPH, 5158 Blackhawk Rd, Aberdeen Proving Ground, Edgewood Area, Aberdeen, MD 21010. E-mail: [email protected]. The work submitted conforms to all governmental regulations and discipline appropriate professional ethical standards. This study was reviewed by the US Army Public Health Command Review Board and deemed to be Public Health Practice (Hodge and Gostin, 2004). Army Regulation 40-5 established the US Army Public Health Command as the Army’s public health agency. Individuals did have the right to refuse to participate. The views expressed in this article are those of the authors and do not reflect official policy or position of the Department of the Army, the Department of Defense, the US Government, or any of the institutional affiliations listed. Copyright * 2013 by Lippincott Williams & Wilkins ISSN: 0022-3018/13/20107Y0572 DOI: 10.1097/NMD.0b013e318298296a

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The current US military operations in Afghanistan and Iraq are the largest and longest-lasting ground combat operations since the Vietnam War. Compared with the Vietnam War, the Korean War, and World War II, fatality rates for physical combat injuries and ground troops killed in action have significantly decreased, which has been often attributed to the improvements in body armor, trauma triage, and surgical techniques during the past several decades (Champion et al., 2003; Gawande, 2004; Holcomb et al., 2006; McSwain et al., 2003; Patel et al., 2004). However, the increasing number of soldiers returning from Iraq and Afghanistan who experience a range of combat exposures may have any number of negative behavioral and psychiatric conditions with no observable wound, creating a unique challenge to accurately diagnose and quantify incidence and prevalence rates. The prevalence of behavioral and psychiatric disorders among OEF/OIF veterans varies widely between samplesVfrom 11% to 17% (Hoge et al., 2006) to 37% (Seal et al., 2009). All deployment combat exposures are not the same, and the differences in rates of behavioral and psychiatric diagnoses across populations may, in part, be explained by specific combat exposures of service members (Dedert et al., 2009; Hoge et al., 2004; Killgore et al., 2008; Larson et al., 2008; Renshaw et al., 2009). Events particularly related to death, including being shot at, handling dead bodies, knowing someone who was killed, and killing an enemy combatant, have been found to be significantly associated with increased negative behavioral and psychiatric symptoms (Hoge et al., 2004; Killgore et al., 2008). Further, a linear increase has been shown between the number of firefights experienced by a soldier and the prevalence of posttraumatic stress disorder (PTSD; Hoge et al., 2004). Although the relationship between being previously deployed, experiencing some specific traumatic combat exposures, and negative behavioral and psychiatric conditions has been studied, there is still a gap in knowledge pertaining to the impact resulting from the cumulative effect of multiple types of combat exposures among active-duty OEF/OIF soldiers. This study was designed to evaluate the association between cumulative combat exposures and negative behavioral and psychiatric conditions among OEF/OIF combat veterans. We concentrated on five outcomes hypothesized to be particularly stressful to soldiers’ personal and professional lives, including self-reported behavioral and psychiatric diagnoses, aggression, problematic alcohol use, physical altercation with a significant other, and criminal behavior. We hypothesized that an increasing number of cumulative combat exposures would be associated with an increased likelihood of each negative behavioral and psychiatric condition.

METHODS Sample This sample was composed of soldiers from two US Army brigade combat teams (BCTs) located at a large military installation in Colorado. A BCT is a modular, combined arms force cable of self-sustaining offensive, defensive, stability, and civil support operations, typically made up of 3000 to 5000 soldiers. As a part of a rapid field investigation conducted by the US Army Public Health Command (USAPHC) Behavioral and Social Health Outcomes

The Journal of Nervous and Mental Disease

& Volume 201, Number 7, July 2013

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Program (Millikan et al., 2009), an anonymous survey was completed by 6128 soldiers (80% of the current BCT soldiers assigned). Soldiers who did not fully answer all questions related to their history of combat exposures were excluded from this analysis (n = 126), resulting in a total sample size of 6002. The soldiers assigned to each BCT were surveyed approximately 6 months after the most recent combat deployment to Iraq (November 2008 and October 2009) of their respective BCT. A large percentage of the soldiers had previously deployed (68%). As a part of this survey, the soldiers were asked to self-report demographic and military characteristics, combat exposures, behavioral health diagnoses and symptoms, and history of criminal behavior. Army Regulation 40-5 established the USAPHC as the Army’s public health agency, and this rapid public health surveillance study was deemed to be Public Health Practice (Hodge and Gostin, 2004). Individual participation was voluntary, and the survey administered was anonymous and nonattributional. The US Army Public Health Command Review Board approved the current rapid field investigation and the dissemination of these main study question findings for the peer-reviewed literature.

Measurement of Demographic and Military Characteristics The soldiers reported their age, sex, ethnicity, education, and marital status and specific military characteristics, including military rank, unit, and the number of previous deployments. Ethnicity was ascertained as white, African-American, Hispanic, Asian/Pacific Islander, and other. The soldiers who previously deployed were asked to complete a 15-item checklist of combat exposures they may have experienced during any of their previous deployments (e.g., ‘‘being attacked or ambushed,’’ ‘‘shooting or directing fire at an enemy,’’ ‘‘knowing someone seriously injured or killed’’). This checklist is similar to those used in previous studies evaluating combat exposures and behavioral and/or mental health outcomes (Booth-Kewley et al., 2010; Bryan et al., 2010; Hoge et al., 2004; Killgore et al., 2008; Wilk et al., 2010).

Measurement of Behavioral and Psychiatric Conditions The soldiers were also asked to self-report behavioral and psychiatric conditions, including alcohol use and history of specific behavioral and psychiatric diagnoses by a medical professional (e.g., depression, PTSD, adjustment disorder). The Rapid Alcohol Problems Screen (RAPS4) was used to identify problematic alcohol use. This four-item measure has good internal sensitivity (0.86) and specificity (0.95; Cherpitel, 2002). Alcohol use was considered problematic if one or more affirmative responses were given (US Department of Health and Human Services, 2003). A brief history of behavioral and psychiatric conditions (e.g., PTSD, adjustment disorder, depression) was solicited in response to a single question that asked ‘‘Has a medical professional ever told you that you have any of the following behavioral health problems,’’ with a list of diagnoses for the respondents to choose one or more.

Measurement of Aggression A modified version of the Conflict Tactics Scale (CTS2) was used to measure physical aggression in this population (Straus et al., 1996). The soldiers were asked to report whether they had committed any minor (five items) and severe (seven items) forms of aggression in the past 12 months. Because this survey was completed 6 months after a recent deployment for some members of this population, the soldiers were specifically instructed not to include acts of physical aggression occurring during combat or training. Minor aggression is defined as fairly common acts that may be viewed as insufficiently dangerous (e.g., threw something at someone, grabbed someone), whereas severe acts of aggression may be definitive indicators of * 2013 Lippincott Williams & Wilkins

Combat and Behavioral Conditions

physical maltreatment and suggest the potential for severe physical assault (e.g., used knife/gun on someone, choked someone; Straus et al., 2003). Traditionally the CTS2 has been used to specifically examine intimate-partner violence; however, in this population, it was adapted to include all acts of overt aggression toward others. Confirmatory factor analysis of the original 12 items of the CTS2 across these scales was conducted, and the reported Cronbach’s > for the Physical Assault Scale was 0.86, with individual item-total correlations ranging from 0.39 to 0.70 (Straus et al., 2003). For each of the 12 items in the CTS2, the soldiers were instructed to indicate the number of times an event had occurred (‘‘1Y2 times, ‘‘3 or more times,’’ or ‘‘never’’ if it did not occur). Because factor analysis supported a single dimension, the total score for each minor and severe physical aggressive acts was calculated by summing all items within each scale, attributing a weighted score of 0 to never, 2 to 1 to 2 times, and 4 to 3 or more times, resulting in a total possible range of 0 to 20 for minor physical aggression and 0 to 28 for severe physical aggression. The soldiers were categorized as having the highest relative levels of minor and severe aggression if their summary score for each item was in the highest quartile. The soldiers were also asked a single question pertaining to whether they had ever had a physical fight with their significant other.

Measurement of Criminal History The soldiers were asked whether they had previously been convicted of specific crimes (e.g., domestic violence, assault, robbery). For any affirmative responses, the soldiers were asked to denote whether the criminal conviction occurred before, or after, joining the army. From these responses, a single outcome variable for criminal behavior was created to indicate whether the soldiers had a history of any criminal conviction since joining the army (yes or no). The assessment of criminal history using self-report measures has been shown to have acceptable reliability (test-retest correlations of Q0.80), acceptable content validity, high construct validity, and moderate to strong criterion validity for most analytic purposes (Hindelang et al., 1981; Thornberry and Krohn, 2000).

Data Analysis Frequency distributions were examined for all of the demographic and military characteristics. The distribution of the soldiers who reported each type of combat exposure was examined for each of the 15 items and was compared with findings reported on similar items reported in earlier study samples (Hoge et al., 2004; Killgore et al., 2008). A summary score for all positively endorsed combat exposures was calculated (i.e., cumulative combat exposures), with a possible range of 0 to 15. The skewness and kurtosis of cumulative combat exposures were assessed to ensure that the distribution was within an allowable level (i.e., T1.0; Bulmer, 1979). The mean number and standard deviation of combat exposures were examined for the soldiers with and without a lifetime history of behavioral and psychiatric conditions, a recent history of relatively high aggression, positive screening for problematic alcohol use, a physical altercation with their significant other, and a criminal conviction since joining the army. Analyses of variance were conducted to assess for significant differences across the subgroups using an > level of less than 0.05. An ordinal variable was created to measure the cumulative number of combat exposures encountered on recent deployments to approximate ‘‘combat intensity’’ and for ease of communication to military leadership. The combat exposure summary score was classified into tertiles (low, moderate, and high) on the basis of the sample distribution (Booth-Kewley et al., 2010). The soldiers who had not previously deployed were classified as having no combat exposures. The mean number and standard deviation of combat exposures were examined within each level of this categorical variable. Median values www.jonmd.com


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TABLE 1. Demographic and Military Characteristics of the Survey Population (N = 6002) Sex Ethnicity

Education

Marital status

Rank

Previous deployments

Male Female White African-American Hispanic Asian/Pacific Islander Other Some high school GED High school Some college/AA College degree Single Married Separated/divorced E1 to E4 E5 to E6 E7 to E9 WO1 to WO5 O1 to O5 None 1 2 Q3

n

%

5456 481 3996 652 778 247 270 58 750 1998 2451 681 2002 3272 671 3522 1570 328 53 440 1946 1913 1372 719

90.9 8.0 66.6 10.9 13.0 4.1 4.5 1.0 12.5 33.3 40.8 11.4 33.4 54.5 11.2 58.7 26.2 5.5 0.9 7.3 32.4 31.9 22.9 12.0

Demographic and military characteristics of the total army for comparability are as follows: men, 87%; white, 70%; GED/high school, 76%; some college, not tracked; married, 59%; E1 to E4, 46%; previously deployed, 72%. Data source: Defense Manpower Data Center, Active Duty (September 2010)/CTS deployment file (December 2010). AA indicates associates degree; CTS, Contingency Tracking System Deployment File; GED, General Educational Development; O, officer; WO, warrant officer.


were examined using the PROC NPAR1WAY in SAS (Wilcoxon’s twosample test), with an > level of less than 0.05, to determine differences across the subgroups. Bivariate and multivariable logistic regression modeling were then conducted to assess the association between this categorical variable (approximating relative combat intensity) and specific behavioral and psychiatric conditions, controlling for potential confounding from demographic (i.e., ethnicity, education, and marital status) and military characteristics (i.e., unit type, rank). These specific demographic and military characteristics were controlled in the analysis because there were significant differences observed between these strata and the exposure and outcomes of interest. The analysis was also replicated, restricting the population to the soldiers with one or zero deployments. All analyses were completed using SAS software version 9.2 (copyright SAS Institute Inc, Cary, NC).

RESULTS Among the 6002 soldiers included in this analysis, the majority self-identified as men (91%), white (66%), having a high school education (33%) or some college (41%), and married (55%; Table 1). This population was also predominantly junior-enlisted (E1 to E4) soldiers (56%), most of whom had previously deployed at least once (68%). The survey population was fairly comparable with the overall army in regard to demographic and military characteristics, although there was a higher proportion of lower enlisted soldiers (E1 to E4) than in the overall army (46%), which is typical of a BCT because it has a high proportion of combat arms soldiers (Defense Manpower Data Center, Active Duty, September 2010). The soldiers reported some specific combat exposures more commonly (e.g., ‘‘received incoming artillery, rocket, or mortar fire’’ [82%] and ‘‘knowing someone seriously injured or killed’’ [80%]) than others (e.g., ‘‘engaging in hand-to-hand combat’’ [4%] and ‘‘being responsible for the death of a nonenemy combatant’’ [12%]; Table 2). Compared with results from an earlier population of soldiers and marines deployed to Iraq in 2003,3 the percentage of soldiers in the current study reporting each specific combat exposure was similar or lower, with the exception of three items that were more commonly reported (i.e., ‘‘had a close call, was shot or hit, but protective gear

TABLE 2. Percentage of the Previously Deployed Population Reporting Specific Combat Exposures (n = 4118) Current Study Population Deployed to Iraq in 2007Y2009

Being attacked or ambushed Receiving incoming artillery, rocket, or mortar fire Shooting or directing fire at an enemy Being responsible for the death of a noncombatant Being responsible for the death of an enemy combatant Seeing dead bodies or human remains Knowing someone seriously injured or killed Participating in demining operations Seeing ill or injured women or children whom you were unable to help Being wounded or injured Had a close call, was shot or hit, but protective gear saved you Had a buddy shot or hit who was near you Clearing or searching homes or buildings Engaging in hand-to-hand combat Saved the life of a soldier or civilian

Soldiers/Marines Deployed to Iraq in 2003(Hoge et al., 2004)

Soldiers Deployed to Iraq in 2006(Killgore et al., 2008)

n

%

% (min-max)

%

2517 3297 2152 475 1364 2972 3172 563 1925 605 992 1292 2301 161 789

62.9 82.3 53.8 11.9 34.1 74.2 79.2 14.1 48.1 15.1 24.8 32.3 57.5 4.0 19.7

89Y95 86Y92 77Y87 14Y28 48Y65 94Y95 86Y87 34Y38 69Y83 9Y14 8Y10 22Y26 80Y86 9Y22 19Y21

59.7 86.3 36.3 3.2 8.8 63.3 79.3 52.0 30.4 7.9 9.5 11.6 53.3 3.1 16.5

Max indicates maximum; min, minimum.

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TABLE 3. Self-Reported History of Behavioral Health Issues and Mean Combat Exposures of the Survey Population (N = 6002) Combat Exposuresf

Total Behavioral/psychiatric health issuea Major aggressionb Minor aggressionb Problematic alcohol usec Physical altercation with significant otherd Criminal behavior since joining the armye

No Yes No Yes No Yes No Yes No Yes No Yes

n

%

Median

Mean

SD

6002 4184 1818 4452 1550 4743 1259 4142 1860 5243 481 5778 224

100.0 69.7 30.3 74.2 25.8 79.0 21.0 69.0 31.0 87.4 8.0 96.3 3.7

3.0 2.0 6.0 3.0 5.0 3.0 5.0 3.0 5.0 3.0 4.0 3.0 6.0

4.1 3.3 6.0 3.8 5.1 3.8 5.4 3.8 4.9 4.0 5.1 4.1 5.6

4.2 3.9 4.3 3.9 4.7 4.0 4.6 4.0 4.5 4.1 4.6 4.2 4.6

p

G0.0001 G0.0001 G0.0001 G0.0001 G0.0001 G0.0001

a

Any self-reported history of behavioral or psychiatric health diagnosis. High levels of aggression in the past 12 months (highest 25% of scores among the survey respondents) (Straus et al., 2003). c Problematic alcohol use (two or more positive responses on the RAPS4 scale) (US Department of Health and Human Services, 2003). d Any self-reported history of a physical altercation with a significant other. e Any self-reported criminal convictions after joining the army. f The soldiers never deployed are coded as having experienced zero combat exposures. b

saved you,’’ current study, 24%, vs. Hoge et al., 8%Y10%); ‘‘had a buddy shot or hit who was near you,’’ current study, 32%, vs. Hoge et al., 2004, 22%Y26%; and ‘‘being wounded or injured,’’ current study, 15%, vs. Hoge et al., 2004, 9%Y14%). Compared with results from an earlier population of soldiers deployed to Iraq in 2006,4 the percentage of soldiers in the current study reporting each specific combat exposure was similar or higher, with the exception of one item that was reported less commonly (i.e., ‘‘participating in demining operations,’’ current study, 14%, vs. Killgore et al., 2008, 52%). Overall, the mean number of combat exposures reported by the soldiers was 4.1 (SD, 4.2; Table 3). The mean number of combat exposures was significantly higher (p G 0.0001) among the soldiers with a history of behavioral and psychiatric conditions (6.0; SD, 4.3) compared with the soldiers reporting no history of behavioral and psychiatric conditions (3.3; SD, 3.9). Similarly, compared with the soldiers reporting no history of each selected outcome, the soldiers reporting relatively higher minor and severe aggression, problematic alcohol use, a physical altercation with a significant other, or a criminal conviction since joining the army also reported a significantly higher (p G 0.0001) mean number of combat exposures. Significance testing of the median number of cumulative exposures was similar to the mean scores. On the basis of the frequency distribution of the total summary of combat exposures, approximate levels of relative combat exposures were categorized as none (nondeployed, n = 1946), low (0Y4 combat exposures, n = 1532), moderate (5Y8 combat exposures, n = 1327), and high (9Y15 combat exposures, n = 1197). The mean number of combat exposures and the standard deviation within each stratum were as follows: low (2.1; SD, 1.4), moderate (6.5; SD, 1.1), and high (10.7; SD, 1.5). Multivariate analyses adjusted for unit type, ethnicity, education, rank, and marital status revealed a trend of increasing associations between all of the outcomes examined and increasing cumulative combat exposures. In comparison with the referent group of soldiers who had not previously deployed, the soldiers categorized as having the highest relative cumulative combat exposures (i.e., ‘‘high combat intensity’’) were significantly more likely to be associated with selfreporting a history of behavioral and psychiatric diagnoses, relatively * 2013 Lippincott Williams & Wilkins

higher severe and minor aggression, problematic alcohol use, a physical altercation with a significant other, and/or a criminal conviction since joining the army (Table 4). In contrast, compared with the referent group of soldiers who had not previously deployed, the soldiers who had deployed but who had the lowest relative combat exposures (i.e., ‘‘low combat intensity’’) were not significantly associated with reporting relatively higher severe and minor aggression, problematic alcohol use, or physical altercations with a significant other. The associations remained significant when we restricted the analysis to the soldiers who had previously deployed only once and the soldiers who had not previously deployed (data not shown).

DISCUSSION The results from this study confirmed the hypothesis that an increasing number of cumulative combat exposures is associated with an increased likelihood of self-reported negative outcomes. Outcomes particularly stressful to soldiers’ personal and professional life such as behavioral and psychiatric diagnoses, aggression, problematic alcohol use, physical altercations with a significant other, and criminal behavior since joining the military were all significantly more likely among the soldiers reporting the highest level of combat exposures. Furthermore, a consistent increasing association was found between cumulative combat exposures and the soldiers reporting behavioral and psychiatric conditions. The soldiers reporting the highest level of combat were more than 6 times more likely to report a history of behavioral and psychiatric diagnoses than those who were never deployed, compared with 1.7 times and 2.9 times for the soldiers who reported low and moderate levels of combat, respectively. This increasing trend was consistent across all behavioral and psychiatric conditions evaluated in the current study but some to a greater or lesser extent. Although the soldiers reporting the highest relative combat exposures were consistently at elevated risk for negative behavioral and psychiatric conditions, the number and/or types of combat exposures may impact subsequent conditions (e.g., aggression, problematic alcohol use) differently. The trend observed between increasing combat exposures and behavioral and psychiatric conditions is consistent with a previous study (Kang et al., 2003) that observed an www.jonmd.com


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TABLE 4. Adjusted ORs and 95% CIs for the Association Between Categorized Cumulative Combat Exposures and Behavioral Outcomes Any Self-Reported Behavioral/ Psychiatric Diagnosesa

Never deployed Combat exposuresf Low Moderate High

Major Aggressionb

Minor Aggressionb

Problematic Alcohol Usec

Physical Altercation With Significant Otherd

Criminal Behavior Since Joining the Armye

OR

95% CI

OR

95% CI

OR

95% CI

OR

95% CI

OR

95% CI

OR

95% CI

1.00

V

1.00

V

1.00

V

1.00

V

1.00

V

1.00

V

1.70 2.90 6.08

1.4Y2.0 2.4Y3.5 5.0Y7.4

0.76 1.38 2.93

0.6Y0.9 1.1Y1.7 2.4Y3.6

0.98 1.71 3.52

0.8Y1.2 1.4Y2.1 2.9Y4.3

0.99 1.95 3.01

0.8Y1.3 1.6Y2.4 2.4Y3.8

0.99 1.12 1.78

0.7Y1.3 0.8Y1.5 1.3Y1.6

1.51 1.60 2.69

1.0Y2.3 1.1Y2.4 1.8Y4.0

ORs adjusted for battalion type, race/ethnicity, education level, rank, and marital status. a Any self-reported history of one or more behavioral or psychiatric health diagnoses by a medical professional. b High levels of aggression in the past 12 months (highest 25% of scores among the survey respondents)25. c Problematic alcohol use (two or more positive responses on the RAPS4 scale).23 d Any self-reported history of a physical altercation with a significant other. e Any self-reported criminal convictions after joining the army. f Levels of cumulative combat exposures among the deployed soldiers were defined by examining the frequency distribution of the total number of events encountered while deployed, as indicated on the 15-item combat exposure scale, and categorizing the responses into tertiles: low (0Y4), moderate (5Y8), and high (9Y15). CI indicates confidence interval; OR, odds ratio.

increasing trend between increasing cumulative combat exposures among Gulf War veterans and an increased likelihood of PTSD. Combat exposures are likely to differ on the basis of the timing, mission, objectives, and theatre of operations, and, as such, the current study sample of soldiers deployed to Iraq in 2007Y2009 reported relatively lower rates of most combat exposures than did a population of soldiers and marines deployed to Iraq in 2003 (Hoge et al., 2004) but relatively higher rates of most combat exposures than did a population of soldiers deployed to Iraq in 2006 (Killgore et al., 2008). However, the current soldier population consistently reported higher rates of injury to themselves and their fellow soldiers compared with both previous study samples (Hoge et al., 2004; Killgore et al., 2008). Previous studies (Hoge et al., 2004; Killgore et al., 2008) have assessed soldiers’ individual combat exposures items to determine those most strongly associated with subsequent behavioral and psychiatric conditions. The majority (62%) of deployed soldiers in the current study endorsed five or more different combat exposures, perhaps reflective of the co-occurrence of multiple combat exposures within a dynamic combat environment. As such, the assessment of individual combat exposures (e.g., being attacked or ambushed) has the potential to artificially inflate the individual relationship between any one combat exposure and specific behavioral and psychiatric conditions. In the current study, the cumulative number of combat exposures was examined after categorization into tertiles in an attempt to account for the dynamic nature of combat and to approximate combat intensity. The data collected for the current study were completed during a rapid field investigation, and, because of survey time and length restrictions, the history of behavioral and psychiatric diagnoses was estimated through the participants self-reporting whether a medical professional had ever told them that they had had a specific behavioral or psychiatric problem. This method is not without limitation, and although all soldiers were advised before completing the survey that the data were being collected anonymously, the possibility of stigma and concerns of confidentiality could have impacted accurate participant reporting. However, the rate of behavioral and psychiatric diagnoses in this survey population (30%) was found to be fairly comparable with the rate of medical encounters for behavioral and psychiatric reasons in a group of soldiers previously and/or currently assigned to the same two BCTs after their most recent 576

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deployment (37%Y41%), as reported using medical encounter data during the broader field investigation (Millikan et al., 2009). Likewise, the rate of behavioral and psychiatric diagnoses reported on the survey was comparable with that of a recent large population study assessing prevalence rates of behavioral and psychiatric diagnoses among veterans seeking care at the Veterans Health Administration (Seal et al., 2009). Given that the behavioral and psychiatric diagnoses rates in the current study are similar to those of similar population comparisons, there is evidence that self-reported diagnoses as a proxy for true diagnosis rates were a suitable estimate in this population. The findings of this study should be considered in conjunction with the following limitations. The combat exposure scale analyzed in this study was modified from a larger 33-item assessment tool created by the Mental Health Advisory Team to assess behavioral health in combat-deployed service members. Although this modified scale has not been standardized, numerous studies have used this tool to assess combat exposure among OEF/OIF veterans in a similar manner (Booth-Kewley et al., 2010; Hoge et al., 2004; Killgore et al., 2008; Wilk et al., 2010). The method of combining combat exposures to estimate cumulative combat exposures does not take into account the relative weight and/or stress associated with each type of combat exposure. On the basis of knowledge of the known risk factors of PTSD, such as trauma severity (Brewin et al., 2000) and perceived life threat (Ozer et al., 2003), it is likely that some combat exposures (e.g., ‘‘seeing ill or injured women or children whom you were unable to help’’ or ‘‘had a close call, was shot or hit, but protective gear saved you’’) are more likely to impact subsequent development of behavioral and psychiatric conditions than are others, and future studies assessing cumulative combat exposures may consider this. Because the soldiers were asked to report any previous combat exposures (not just those during the most recent deployment), the possibility exists that the observed associations were the result of the soldiers having multiple deployments with a higher number of combat exposures. To determine the extent to which multiple deployments of combat exposures versus multiple combat exposures during a single deployment were associated with negative behavioral and psychiatric conditions, we performed an ad hoc analysis among the soldiers with only one or zero deployments. The results of these ad hoc analyses were not statistically different from those observed * 2013 Lippincott Williams & Wilkins




among soldiers with more than one deployment, indicating that cumulative combat exposures were highly associated with negative behavioral conditions, regardless of the number of previous deployments. There is also the possibility that a number of nondeployed soldiers with similar exposures (e.g., seeing dead bodies, knowing someone who was seriously killed or injured) in a nondeployed setting were misclassified; however, this would have resulted in misclassification bias toward the null and an underestimate of measures of association. Because of the cross-sectional nature of the study and this analysis, it was impossible to assess the temporal nature of the relationship between combat exposures and the subsequent development of behavioral and psychiatric conditions. However, a previous longitudinal analysis of OEF/OIF soldiers, evaluating outcomes before and after deployment, found that up to 76% of new self-reported PTSD symptoms could be attributable to combat exposures among previously deployed service members (Smith et al., 2008). Self-reported measures of criminal behavior have been shown to be underreported in some populations (Thornberry and Krohn, 2000), and differential reporting may or may not be true for some specific race-sex groups (Farrington et al., 1996; Hindelang et al., 1981; Huizinga and Elliot, 1986). However, the current study survey was anonymous to encourage honest self-reporting among the soldiers who may be hesitant to honestly report their complete history of criminal convictions since joining the military. The extent that there would be differential reporting with respect to the soldiers’ level of combat exposure is unclear. Lastly, this analysis, based on survey data collected within a single active-duty army population, may not be representative of all deployment exposures of service members, although the observed proportion of the soldiers’ individual combat exposures was fairly similar to those in previous studies.

CONCLUSIONS This study provides further evidence of an association between cumulative combat exposures among soldiers previously deployed to Iraq and an increasing likelihood of several different types of negative behavioral and psychiatric conditions. The magnitude and the consistency of the association among the group of soldiers with the highest number of combat exposures and negative behavioral and psychiatric conditions suggest that the cumulative number of combat exposures is an important consideration for identifying high-risk soldiers and units returning from combat deployments. Among the growing cohort of OIF/OEF veterans returning from combat deployments, understanding the causal predictors of negative behavioral and psychiatric conditions is imperative to help effectively treat and mitigate future development of behavioral and psychiatric conditions; however, more longitudinal research in this area is necessary to garner a deeper understanding of this temporal relationship. Clinicians and leaders alike should be aware that not all service members deployed at the same time, or even within the same unit, may have had the same combat exposures, and thus, individual development of behavioral and psychiatric conditions is likely to vary among soldiers returning from combat deployments. DISCLOSURE The authors declare no conflict of interest. REFERENCES Booth-Kewley S, Larson GE, Highfill-McRoy RM, Garland CF, Gaskin TA (2010) Factors associated with antisocial behavior in combat veterans. Aggress Behav. 36:330Y337. Brewin CR, Andrews B, Valentine JD (2000) Meta-analysis of risk factors for posttraumatic stress disorder in trauma-exposed adults. J Consult Clin Psychol. 68:748Y766.



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