A Longitudinal Comparison of Posttraumatic Stress Disorder and ...

Military Psychology 2014, Vol. 26, No. 2, 77– 87

© 2014 American Psychological Association 0899-5605/14/$12.00 http://dx.doi.org/10.1037/mil0000034

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A Longitudinal Comparison of Posttraumatic Stress Disorder and Depression Among Military Service Components Emma K. Schaller

Kelly A. Woodall

San Diego State University

Independent Scholar, Memphis, Tennessee

Hector Lemus

Susan P. Proctor


U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts

Dale W. Russell

Nancy F. Crum-Cianflone

Uniformed Services University of the Health Sciences


The purpose of this study was to longitudinally investigate PTSD and depression between Reserve, National Guard, and active duty continuously and dichotomously. The study consisted of Millennium Cohort Study participants and used self-reported symptoms. Repeated measures modeling assessed PTSD and depression continuously and dichotomously over time. A subanalysis among only recently deployed personnel was conducted. Of the 52,653 participants for the PTSD analysis, the adjusted PCL-C means were 34.6 for Reservists, 34.4 for National Guardsmen, and 34.7 for active duty members, respectively. Of the 53,073 participants for depression analysis, the adjusted PHQ-9 means were 6.8, 6.7, and 7.2, respectively. In dichotomous models, Reservists and National Guardsmen did not have a higher risk of PTSD or depression compared with active duty members. Among deployers, Reservists and National Guardsmen had higher odds (odds ratio ⫽ 1.16, 95% confidence limit [CL] [1.01, 1.34] and OR ⫽ 1.19, 95% CL [1.04, 1.36], respectively) of screening positive for PTSD, but not depression. Although Reserve and National Guard deployers had modestly increased odds of PTSD compared with active duty members, overall there were minimal differences in the risk and symptom scores of PTSD and depression between service components. Keywords: PTSD, depression, active duty, National Guardsmen, Reservists

During the recent conflicts in Iraq and Afghanistan, nearly half of the deployed U.S. military personnel were Reservists and National

Guardsmen (Polusny et al., 2011). Although deployment locations and lengths are typically similar to active-duty members, Reserve and National Guard personnel may face additional challenges, including decreased physical and mental preparedness for deployments, longterm absences from civilian jobs, and reintegration to civilian life upon their return (Doyle & Peterson, 2005; J. Griffith, 2011; Lane, Hourani, Bray, & Williams, 2012). Despite the large number of deployed Reserve and National Guard members, mental health issues within these groups have not been as thoroughly investigated compared with their active-duty counterparts (Riviere, Kendall-Robbins, McGurk, Castro, & Hoge, 2011).

Emma K. Schaller, Public Health Department, San Diego State University; Kelly A. Woodall, Independent Scholar, Memphis, Tennessee; Hector Lemus, Public Health Department, San Diego State University; Susan P. Proctor, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts; Dale W. Russell, Uniformed Services University of the Health Sciences; Nancy F. Crum-Cianflone, Public Health Department, San Diego State University. Correspondence concerning this article should be addressed to Emma K. Schaller, Public Health Department, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182. E-mail: [email protected] 77


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Research to date has shown that Reservists and National Guardsmen may have a higher rate of mental health problems after deployment compared with active-duty members (Kline et al., 2010; Riviere et al., 2011; Vasterling et al., 2010). Although previous studies have found similar rates of mental health problems among National Guard and active-duty service members immediately after deployment, National Guard personnel were 47% and 38% more likely to report symptoms of depression and posttraumatic stress disorder (PTSD), respectively, at 12 months post-deployment compared with active-duty members (James Griffith, 2010; Milliken, Auchterlonie, & Hoge, 2007; Thomas et al., 2010). Furthermore, symptoms of PTSD may persist for many years following onset and may be comorbid with depressive symptoms, hence longitudinal analyses are critical to understand how these mental health symptoms fluctuate over time by service component (T. C. Smith et al., 2009; Wells et al., 2010). Although previous studies have cited concern for potentially higher rates and severity scores for PTSD and depression among Reservists and National Guardsmen, these studies lacked longterm assessment of PTSD and depression symptoms or did not specifically compare Reservist and National Guard personnel with their activeduty counterparts while accounting for deployment status (Kline et al., 2010; Riviere et al., 2011; Thomas et al., 2010). Because postdeployment support for Reserve and National Guard members may differ by service branch, it is also critically important to investigate mental health outcomes by service branch and deployment status. The main objective of this study was to longitudinally investigate PTSD and depression between Reserve, National Guard, and active-duty personnel by service branch, while adjusting for deployment-related characteristics and other relevant covariates. Method Study Population The Millennium Cohort Study is a large population-based cohort designed to evaluate the long-term health effects of military service. The Cohort consists of active duty, Reserve, and National Guard personnel from all branches of

service and collects follow-up data approximately every 3 years regardless of current military status (T. C. Smith, 2009). Participants were randomly selected from U.S. military personnel as previously described (Crum-Cianflone, 2013; T. C. Smith, 2009). The first panel (2001–2003) enrolled 77,047 consenting participants, of whom 55,021 (71%) completed a first follow-up questionnaire (2004 –2006), and 54,790 (71%) completed a second follow-up questionnaire (2007–2008). This study included participants who completed a baseline (2001– 2003) and at least one follow-up (2004 –2006 and/or 2007–2008) questionnaire (n ⫽ 63,370/ 77,019 [82%]). Those with incomplete outcome and covariate data (n ⫽ 9899 for PTSD population and n ⫽ 9479 for depression population) and those who changed service branches over the 6-year follow-up period (n ⫽ 818) were excluded from the PTSD and depression study populations. The final PTSD and depression study populations included 52,653 and 53,073 participants, respectively. Military Component and Service Branch Component status (Reserve, National Guard, and active duty) and service branch (Army, Air Force, Navy, Marine Corps, and Coast Guard) were determined using data files from the Defense Manpower Data Center (DMDC). For all the models, component status was determined at baseline. PTSD and Depression PTSD and depression were measured longitudinally using self-reported responses on the baseline and follow-up surveys. Because our population included active duty, reservists, national guardsmen, and individuals separated from the military, the standardized PTSD Checklist-Civilian Version (PCL-C) was used to assess PTSD symptoms rather than the PTSD Checklist-Military Version (PCL-M). Symptom severity for PTSD was assessed using continuous PCL-C scores. Scores range from 17 to 85, and a score of 50 or above suggests high symptom severity and possible functional impairment (Diagnostic and Statistical Manual of Mental Disorders, fourth edition [DSM–IV]; Monson et al., 2008; Thomas et al., 2010). PTSD was also assessed using dichotomous outcomes (yes/no) based on DSM–IV criteria


PTSD AND DEPRESSION BETWEEN MILITARY COMPONENTS

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(screening positive for 1 intrusion symptom, 3 avoidance, and 2 hyperarousal symptoms) for the PCL-C. The 9 depression items from the Patient Health Questionnaire (PHQ) were used to assess depression symptoms. Depression symptom severity was assessed using continuous PHQ-9 scores that range from 0 to 27. Cut-off points have previously been determined for mild (5), moderate (10), moderately severe (15), and severe depression (20; Kroenke, Spitzer, & Williams, 2001; Manea, Gilbody, & McMillan, 2012). Depression was also assessed using dichotomous outcomes (yes/no) using a cutpoint of 10 or greater on the PHQ-9. The screening criteria for PTSD and depression, which produce dichotomous outcomes, have been validated among both civilian and military populations, and characterized by high specificity and sensitivity values for both PCL-C (specificity ⫽ 0.99, sensitivity ⫽ 0.60) and PHQ-9 (specificity ⫽ 0.89, sensitivity ⫽ 0.85; Bliese et al., 2008; Fann et al., 2005; Kroenke et al., 2001; Manea et al., 2012; Monson et al., 2008).

deployers were defined by at least one deployment between the baseline and follow-up. Deployers were further categorized by combat experience based on self-report of at least one positive response to personally witnessing death, trauma, injuries, prisoners of war, or refugees. In addition, cumulative days deployed and number of deployments were both included in a supplementary analysis of deployers.

Demographics and MilitarySpecific Characteristics

Statistical Analysis

Demographic and military-specific characteristics were obtained from the Department of Defense electronic personnel files managed by the DMDC. Factors assessed at baseline included sex (male, female), birth year (before 1960, 1960 –1969, 1970 –1979, 1980 or later), education (some college or less, bachelor’s or higher degree), race/ethnicity (non-Hispanic White, non-Hispanic Black, other), marital status (never married, married, other), pay grade (junior enlisted, senior enlisted, junior officer, senior officer), and occupation (combat specialist, health care specialist, other). Date of military separation, and in and out of theater dates for those deployed in support of the operations in Iraq and Afghanistan, were also obtained from DMDC. For this study, deployment and military separation status were utilized as time-dependent variables. Separation status was assessed before baseline and between each of the follow-up surveys. Participants were classified as deployers at baseline if they had at least 1 deployment in support of the recent conflicts before completion of the baseline survey. At follow-up,

Behavioral Characteristics Based on baseline questionnaire responses to smoking at least 100 cigarettes and quitting, participants were categorized as a never, past, or current smoker. Problem drinking was assessed using the PHQ-5, which asks questions about alcohol-related incidents, such as missing work or school as a result of drinking, or driving after drinking too much, occurring more than once in the last 6 months (Grucza, Przybeck, & Cloninger, 2008). A participant with an affirmative self-report at baseline to any of the five items was classified as a problem drinker (Spitzer et al., 1994).

Descriptive statistics and univariate analyses were conducted to examine the covariates and the mental health outcomes by service component. After longitudinal data assumptions were evaluated as being met, repeated-measures modeling was conducted to assess the unadjusted and adjusted associations of PTSD and depression symptom severity scores between Reserve, National Guard, and active-duty members. Similar models were performed using the dichotomous outcomes for PTSD and depression. The severity score models were repeated and restricted to service members who had screened positive for PTSD (meeting the DSM–IV criteria) or depression (PHQ-9 ⱖ 10; Bliese et al., 2008; Monson et al., 2008). Secondary models for both PTSD and depression were performed, stratified by service branch. All models were adjusted for demographics, military characteristics, behavioral characteristics, and baseline mental health symptoms. Additional subanalyses were conducted. A deployer-only model was performed and adjusted for cumulative days deployed and number of deployments to assess whether these additional deployment-specific characteristics

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influenced PTSD and depression. These deployer-only models were assessed using both continuous and dichotomous outcomes for PTSD and depression. Data management and statistical analysis were performed using SAS software version 9.3 (IBM, Armonk, NY).


Results A total of 52,653 and 53,073 participants were included in PTSD and depression study populations, respectively. Of the study population utilized for the PTSD models, 57% were active duty, 22% were Reserve, and 21% were National Guard members (see Table 1). Reservists were proportionally more likely than active duty and National Guard personnel to be female, born before 1960, have a bachelor’s degree or higher, be divorced, widowed, or separated, be senior officers, nonsmokers, never deployed, and not have separated from military service before completion of the last follow-up survey. National Guardsmen were proportionally more likely than active duty personnel and Reservists to be male, non-Hispanic White, have some college education or less, enlisted, in the Army, have an occupation other than health care or combat specialist, be a past smoker, and have alcohol-related problems (see Table 1). The depression population was nearly identical to the PTSD population shown in Table 1 (data not shown). Based on the screening criteria, 3.9% of active-duty members, 4.0% of National Guardsmen, and 3.5% of Reserve personnel screened positive for PTSD at baseline. After the last follow-up was completed, 9.0% of active-duty members, 10.0% of National Guardsmen, and 8.5% of Reserve personnel screened positive for PTSD. In the adjusted model, active-duty members had slightly higher PTSD severity scores (M ⫽ 34.7) compared with National Guard personnel (M ⫽ 34.4, p ⬍ .05), but their scores were not significantly different from Reserve personnel (M ⫽ 34.6; see Table 2). When stratified by service branch, the same pattern was observed among Army personnel: active-duty members (M ⫽ 36.2) had slightly higher PTSD symptom severity scores than Army National Guardsmen (M ⫽ 35.6; p ⬍ .05), but did not differ statistically from Reservists (M ⫽ 36.1; see Table 2). Among the Navy/Coast Guard, active-duty

members (M ⫽ 33.2) had higher PTSD symptom severity scores than Reserve personnel (M ⫽ 32.8; p ⬍ .05). There were no significant differences in PTSD scores by component in the Marine Corps or Air Force. Reserve and National Guard members did not have significantly higher odds of screening positive for PTSD when examining all service members together. In models stratified by service branch, Air Force Reservists had higher odds of screening positive for PTSD (odds ratio [OR] ⫽ 1.30; 95% confidence limit [CL] [1.02, 1.64] compared with active-duty members in the Air Force, but no other Reserve or Guard members in the other service branches had significantly higher odds of PTSD. In an analysis restricted to those who screened positive for PTSD (meeting the DSM–IV criteria) on 1 or more questionnaires, mean scores were not significantly different by component (data not shown). Baseline rates for screening positive for depression were 6.1% for active-duty members, 4.9% for National Guardsmen, and 4.9% for Reservists, whereas 7.2%, 6.7%, and 6.5%, respectively, screened positive during the follow-up period. In the fully adjusted depression model, active-duty members had slightly higher, but significant, mean depression severity scores compared with those in the other components (active duty ⫽ 7.2, National Guard ⫽ 6.7, Reserve ⫽ 6.8; all p ⬍ .05; see Table 3). In the depression models stratified by service branch, active-duty members had slightly higher depression scores than National Guard and/or Reserve personnel in each of the service branches (all p ⬍ .05; see Table 3). In the dichotomous models, National Guard personnel had lower odds of depression compared with active-duty members when examining all service members combined (OR ⫽ 0.83, 95% CL [0.74, 0.92]. In the models stratified by service branch there were no significant differences, except Army National Guardsmen had decreased odds of depression compared with Army active-duty members (OR ⫽ 0.83, 95% CL [0.74, 0.94]; see Table 3). In an analysis among those who screened positive for depression on 1 or more questionnaires, Reservists had a slightly lower mean score than active duty and National Guard


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Table 1 Baseline Characteristics of Millennium Cohort Participants in the PTSD Model (n ⫽ 52,653) PTSD population


Characteristicsa Sex Male Female Birth year Pre-1960 1960–1969 1970–1979 1980⫹ Race/ethnicity Non-Hispanic White Non-Hispanic Black Other Education Some college or less Bachelor’s degree or higher Marital status Never married Married Other Military pay gradeb Junior enlisted Senior enlisted Junior officer Senior officer Service branchc Air Force Army Marine Corps Navy/Coast Guard Occupation Other Combat specialist Health care specialist Smoking status Nonsmoker Past smoker Current smoker Alcohol-related problemsd No Yes Deploymente Not deployed Deployed without combat Deployed with combat Separatedf No Yes

Active duty (n ⫽ 30,033) n (%)

National Guard (n ⫽ 11,127) n (%)

Reserve (n ⫽ 11,493) n (%)

23,019 (76.7) 7,014 (23.4)

8,685 (78.1) 2,442 (22.0)

7,471 (65.0) 4,022 (35.0)

3,878 (12.9) 12,788 (42.6) 12,002 (40.0) 1,365 (4.6)

3,907 (35.1) 4,082 (36.7) 2,657 (23.9) 481 (4.3)

4,504 (39.2) 4,400 (38.3) 2,175 (18.9) 414 (3.6)

19,566 (65.1) 3,901 (13.0) 6,566 (21.9)

9,333 (83.9) 791 (7.1) 1,003 (9.0)

8,677 (75.5) 1,584 (13.8) 1,232 (10.7)

21,367 (71.2) 8,666 (28.8)

8,464 (76.1) 2,663 (23.9)

7,646 (66.5) 3,847 (33.5)

8,119 (27.1) 20,417 (68.0) 1,497 (5.0)

2,782 (25.0) 7,358 (66.1) 987 (8.9)

3,139 (27.3) 7,190 (62.6) 1,164 (10.1)

6,878 (22.9) 15,681 (52.1) 4,160 (13.9) 3,360 (11.2)

2,758 (24.8) 6,609 (59.3) 771 (6.9) 1,003 (9.0)

2,045 (17.8) 5,991 (52.0) 1,185 (10.3) 2,291 (19.9)

9,410 (31.3) 11,645 (38.8) 1,853 (6.2) 7,125 (23.7)

3,847 (34.6) 7,280 (65.4)

2,974 (25.9) 5,489 (47.7) 466 (4.1) 2,564 (22.3)

20,303 (67.6) 6,717 (22.3) 3,013 (10.0)

8,001 (72.0) 2,362 (21.2) 764 (6.9)

7,835 (68.2) 1,789 (15.6) 1,869 (16.2)

17,662 (58.3) 7,382 (24.5) 5,221 (17.2)

5,933 (53.0) 3,172 (28.3) 2,099 (18.7)

7,054 (60.9) 2,925 (25.2) 1,625 (13.9)

27,076 (90.2) 2,957 (9.9)

9,469 (85.1) 1,658 (14.9)

10,228 (89.0) 1,265 (11.0)

15,951 (53.2) 6,583 (21.9) 7,499 (24.9)

6,607 (59.4) 2,079 (18.7) 2,441 (21.9)

7,801 (67.8) 1,695 (14.8) 1,997 (17.4)

19,516 (65.0) 10,517 (35.0)

9,630 (86.6) 1,497 (13.5)

10,447 (90.9) 1,046 (9.1)

Note. PTSD ⫽ posttraumatic stress disorder. a Univariate chi-square statistics of military component status (Reserve vs. active duty and National Guard vs. active duty) revealed that all characteristics were statistically significant at the p ⬍ .05 level. Percentages may not sum to 100 because of rounding. b Military pay grade: junior enlisted (E1–E4), senior enlisted (E5–W5), junior officer (O1–O3), and senior officer (O4 –O9). c Service branch does not have a National Guard. d Alcohol-related problems evaluated using the Patient Health Questionnaire. e Ever deployed between 2001 and last follow-up survey completed. f Separated before completion of the last follow-up survey.

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Table 2 Longitudinal Repeated-Measures Modeling for PTSD Assessed Continuously and Dichotomously by Component and Service Branch (n ⫽ 52,653)


Component/Service branch Component Active duty National Guard Reserve Service branchc Army Active duty National Guard Reserve Air Force Active duty National Guard Reserve Navy/Coast Guardd Active duty Reserve Marine Corpsd Active duty Reserve

Unadjusted symptom Fully adjusted symptom Fully adjusted OR severity scores severity scoresa (95% CL)b 23.4e,f 22.5e 22.2f

34.7e 34.4f 34.6e,f

1.00 1.03 (0.94, 1.13) 1.03 (0.94, 1.13)

23.8e 23.4f 23.4f

36.2e 35.6f 36.1e

1.00 0.99 (0.90, 1.10) 0.99 (0.88, 1.11)

20.7e 20.8e 20.6e

32.6e 32.9e 32.9e

1.00 1.19 (0.97, 1.46) 1.30 (1.02, 1.64)

22.1e 21.4f

33.2e 32.8f

1.00 1.08 (0.88, 1.33)

22.6e 22.4e

35.4e 35.6e

1.00 1.03 (0.68, 1.54)

Note. CL ⫽ confidence limit; OR ⫽ odds ratio; PTSD ⫽ posttraumatic stress disorder. a PTSD severity scores were assessed continuously using the PCL-C. Scores may range from 17 to 85. Model is adjusted for component status, time, sex, birth year, race/ethnicity, education, marital status, military pay grade, service branch, occupation, deployment status, separation status, baseline smoking status, alcohol-related problems, and baseline depression symptoms. b PTSD assessed using dichotomous outcomes based on the Diagnostic and Statistical Manual of Mental Disorders, fourth edition criteria. Model is adjusted for component status, time, sex, birth year, race/ethnicity, education, marital status, military pay grade, service branch, occupation, deployment status, separation status, baseline smoking status, alcohol-related problems, and baseline depression symptoms. c Stratified by service branch. d Service branch does not have National Guard. e,f Letters that are different indicate statistically significant differences (p ⬍ .05) of adjusted means. Same letters indicate no statistically significant differences in means. Tukey’s method was used to adjust for multiple comparisons.

personnel (11.7 vs. 12.2 vs. 12.0, respectively; data not shown). In the subanalysis that included only service members who deployed, significant differences in PTSD scores were not observed using the continuous outcome. When PTSD was assessed dichotomously, deployed Reserve and National Guard members had higher odds of screening positive for PTSD (OR ⫽ 1.16, 95% CL [1.01, 1.34]; and OR ⫽ 1.19, 95% CL [1.04, 1.36], respectively) compared with deployed active-duty members (see Table 4). No significant differences in depression were observed among deployed Reserve and National Guard members compared with active-duty members using dichotomous depression outcomes. However, when

assessed continuously active-duty members had significantly higher depression scores compared with National Guard and Reserve members (see Table 4). Discussion The findings from this study suggest that Reservists and National Guardsmen do not have significantly higher mean PTSD or depression severity scores or increased odds of screening positive for PTSD or depression compared with active-duty members over approximately 6 years of follow-up. In models restricted to deployers and adjusted for deployment-related experiences, Reservists and National Guardsmen have modest, yet significant, increased odds of


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Table 3 Longitudinal Repeated-Measures Modeling for Depression Assessed Continuously and Dichotomously by Component and Service Branch (n ⫽ 53,073)


Component/Service branch Component Active duty National Guard Reserve Service branchc Army Active duty National Guard Reserve Air Force Active duty National Guard Reserve Navy/Coast Guardd Active duty Reserve Marine Corpsd Active duty Reserve

Unadjusted symptom Fully adjusted symptom Fully adjusted OR severity scores severity scoresa (95% CL)b 2.5e 2.3f 2.2f

7.2e 6.7f 6.8g

1.00 0.83 (0.74, 0.92) 0.93 (0.84, 1.03)

3.1e 2.6f 2.7g

7.5e 7.0f 7.2g

1.00 0.83 (0.74, 0.94) 0.97 (0.85, 1.10)

1.9e 1.7f 1.6f

6.7e 6.5f 6.5f

1.00 0.89 (0.70, 1.13) 0.87 (0.67, 1.14)

2.5e 1.9f

7.1e 7.0f

1.00 0.89 (0.53, 1.50)

2.5e 2.1f

6.9e 6.5f

1.00 1.00 (0.80, 1.26)

Note. CL ⫽ confidence limit; OR ⫽ odds ratio; PHQ ⫽ Patient Health Questionnaire; PTSD ⫽ posttraumatic stress disorder. a Depression severity scores were assessed continuously using the PHQ-9. Scores may range from 0 to 27. Model is adjusted for component status, time, sex, birth year, race/ethnicity, education, marital status, military pay grade, service branch, occupation, deployment status, separation status, baseline smoking status, alcohol-related problems, and baseline PTSD symptoms. b Depression assessed using dichotomous outcomes specified by a cut point of 10. Model is adjusted for component status, time, sex, birth year, race/ethnicity, education, marital status, military pay grade, service branch, occupation, deployment status, separation status, baseline smoking status, alcohol-related problems, and baseline PTSD symptoms. c Stratified by service branch. d Service branch does not have National Guard. e,f,g Letters that are different indicate statistically significant differences (p ⬍ .05) of adjusted means. Same letters indicate no statistically significant differences in means. Tukey’s method was used to adjust for multiple comparisons.

PTSD compared with their active-duty counterparts, but there were no significant differences in reported PTSD symptom severity over time. The finding of increased odds of PTSD among deployed Reserve and National Guard members is consistent with several previous studies and highlights the importance of deployment-related experiences on PTSD (Vasterling et al., 2010). Reentry, reintegration, and recovery after deployment play a vital role in the mental health of military personnel (Doyle & Peterson, 2005). For instance, on return from deployment, Reservists and National Guardsmen may lack the social support received by active-duty members (Doyle & Peterson, 2005; J. Griffith, 2011). In addition, Reservists and

National Guardsmen are more likely to report concerns about family and relationship disruptions than are their active-duty counterparts (Vogt, Samper, King, King, & Martin, 2008). Both financial hardship and unemployment can independently increase the risk for depression and PTSD (Riviere et al., 2011). For example, in a prior study of National Guard members, those reporting financial difficulties 12 months after deployment were more likely to report depression and PTSD than those not reporting financial difficulties (Riviere et al., 2011). Although there are numerous reasons or mechanisms that could lead to increased mental health morbidity among Reserve and National Guard members, results from this study indicate

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Table 4 Longitudinal Repeated-Measures Modeling for PTSD and Depression Assessed Continuously and Dichotomously Among Deployed Participants


Condition PTSDb (n ⫽ 22,294) Component Active duty National Guard Reserve Depressionc (n ⫽ 22,440) Component Active duty National Guard Reserve

Fully adjusted symptom severity scoresa

Fully adjusted OR (95% CL)a

33.8d 33.7d 33.9d

1.00 1.19 (1.04, 1.36) 1.16 (1.01, 1.34)

3.3d 2.8e 3.0e

1.00 0.92 (0.78, 1.08) 1.04 (0.89, 1.14)

Note. CL ⫽ confidence limit; OR ⫽ odds ratio; PTSD ⫽ posttraumatic stress disorder. a Adjusted for component status, time, sex, birth year, race/ethnicity, education, marital status, military pay grade, service branch, occupation, deployment with or without combat, number of deployments, cumulative days deployed, separation status, smoking status, and alcoholrelated problems. b Adjusted for baseline depression. c Adjusted for baseline PTSD. d,e Letters that are different indicate statistically significant differences (p ⬍ .05) of adjusted means. Same letters indicate no statistically significant differences in means. Tukey’s method was used to adjust for multiple comparisons.

only a weak association between component status and PTSD among deployers, and no association between component status and depression or PTSD symptom severity scores over the approximate 6 years of follow-up. This suggests that the increased risk of PTSD may be shortlived among Reservists and Guardsmen, and may be not substantially different from activeduty members, especially when examined over the long term. It is also possible that variations in time after deployment may account for some of the findings. The existing literature suggests that the timeframe between post-deployment and symptom assessment plays an important role in the rates and severity of both PTSD and depression symptoms. For example, although there is evidence that National Guard personnel are more likely than active-duty members to report symptoms of depression and PTSD at 12 months post-deployment, other studies have found similar rates of mental health problems between these components immediately after deployment (James Griffith, 2010; Milliken et al., 2007; Thomas et al., 2010). Although the overall population of Reservists and National Guardsmen in our study did not experience higher rates of PTSD or depression compared with active-duty members over the 6-year fol-

low-up period, perhaps Reservists and National Guardsmen experienced higher rates of these conditions at certain intervals during the study period. In this study, survey data were administered at specific intervals (approximately every 3 years) unrelated to the timing of deployments. This study is unique because it assessed military personnel from all service components for approximately 6 years including both nondeployed military personnel and personnel with multiple deployments. Previous studies in the U.S. military have been limited to a 12-month follow-up period. One study conducted by Harvey and colleagues followed United Kingdom Reservists for 5 years (Harvey et al., 2011). This study found that Reservists were at higher risk of PTSD approximately 16 months after deployment; however, five years after returning from deployment, the majority of Reservists did not have PTSD. This finding is consistent with our study and suggests that although deployed Reservists may experience higher odds of PTSD symptoms, this appears to be transient, and they do not experience elevated symptom severity scores long term. Improving access to health care, social support, and reintegration into the civilian sector may account for the



observed long-term mental health improvement (Werber et al., 2008). In this study, Reservists and National Guardsmen did not have increased odds of depression compared with active-duty members in the overall sample or among deployers. We found that active-duty members had statistically significantly higher severity scores especially for depression, however the magnitude of differences was small and may not be clinically meaningful. For the PCL-C and PHQ-9, it has been suggested that a 10- to 20- and 5-point change, respectively, is clinically significant in terms of disease symptom severity (Kroenke et al., 2001; Manea et al., 2012). This study has several limitations. The Millennium Cohort data consisted of a sample of responders who may not be representative of all military personnel. However, prior studies have shown that the study population is representative, reports information reliably, and that participation is not influenced by poor health before enrollment (Chretien et al., 2007; LeardMann et al., 2007; Riddle et al., 2007; Ryan et al., 2007; B. Smith, C. A. LeardMann et al., 2007; B. Smith, Smith, Gray, Ryan, & the Millennium Cohort Study Team, 2007; B. Smith, D. L. Wingard et al., 2007; T. C. Smith, I. G. Jacobson et al., 2007; Tyler C. Smith, Smith, Jacobson, Corbeil, & Ryan, 2007; T. C. Smith, M. Zamorski et al., 2007; Wells et al., 2008). Compared with those completing both follow-up surveys, military personnel completing only 1 follow-up survey had statistically higher PTSD (M ⫽ 22.1 vs. M ⫽ 23.3, respectively; p ⬍ .05) and depression (M ⫽ 2.3 vs. M ⫽ 2.8, respectively; p ⬍ .05) scores at first follow- up, although the magnitude of these differences was small. Further, a sensitivity analysis assessing differences between follow-up survey completions found no significant differences by component. Although the assessments of PTSD and depression utilized validated survey instruments (PCL-C and PHQ), these surveys are surrogates for a clinician diagnosis so they may not necessarily reflect clinical presentation of PTSD and depression. Mental health treatment data were not available to include in the models, which may impact severity scores over time. Despite the limitations, several strengths should be noted. This is the first study to longitudinally assess PTSD and depression among

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Reservists, National Guardsmen, and activeduty members in a population-based cohort, while additionally stratifying by service branch and adjusting for several potential confounders. Additionally, continuous PTSD and depression scores were utilized, which can reveal small changes in symptom severity over time. The PCL-C and PHQ may also capture a greater burden of disease because many participants with symptoms may not seek treatment for myriad reasons including fear of stigma (Kim, Thomas, Wilk, Castro, & Hoge, 2010). Although a PTSD diagnostic tool is available for military populations (i.e., PTSD ChecklistMilitary version), the PCL-C was used to capture PTSD symptoms that occurred after service time or that may have resulted from nonmilitary experiences. Because our population included active duty, reservists, national guardsmen, and individuals separated from the military, the PCL-C version allowed us to monitor PTSD symptoms throughout the study period rather than only during active service time. In addition, the PCL-C is the most commonly used diagnostic tool for PTSD in adults and has been used in several other military studies and, therefore, allows consistent and understandable results across multiple studies (Brewin, 2005). In summary, with the exception of the deployment model, overall, Reservists and National Guardsmen did not have significantly higher odds of or mean symptom severity scores for PTSD and depression compared with activeduty members over time. Mean scores of PTSD and depression remained low throughout the follow-up period among all the components, with the majority of the participants (89%) never screening positive for PTSD or depression over the approximate 6-year follow-up period. Our findings are reassuring because they suggest that National Guardsmen and Reservists are not at increased risk for higher PTSD and depression severity scores over the long-term (6-year time frame) compared with active-duty members. References Bliese, P. D., Wright, K. M., Adler, A. B., Cabrera, O., Castro, C. A., & Hoge, C. W. (2008). Validating the Primary Care Posttraumatic Stress Disorder screen and the Posttraumatic Stress Disorder


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(2007). The physical and mental health of a large military cohort: Baseline functional health status of the Millennium Cohort. BMC Public Health, 7, 340. doi:10.1186/1471-2458-7-340 Spitzer, R. L., Williams, J. B., Kroenke, K., Linzer, M., deGruy, F. V., Hahn, S. R., . . . Johnson, J. G. (1994). Utility of a new procedure for diagnosing mental disorders in primary care. The PRIME-MD 1000 study. JAMA: Journal of the American Medical Association, 272, 1749 –1756. doi:10.1001/ jama.1994.03520220043029 Thomas, J. L., Wilk, J. E., Riviere, L. A., McGurk, D., Castro, C. A., & Hoge, C. W. (2010). Prevalence of mental health problems and functional impairment among active component and National Guard soldiers 3 and 12 months following combat in Iraq. Archives of General Psychiatry, 67, 614 – 623. Vasterling, J. J., Proctor, S. P., Friedman, M. J., Hoge, C. W., Heeren, T., King, L. A., & King, D. W. (2010). PTSD symptom increases in Iraqdeployed soldiers: Comparison with nondeployed soldiers and associations with baseline symptoms, deployment experiences, and postdeployment stress. Journal of Traumatic Stress, 23, 41–51. doi:10.1002/jts.20487 Vogt, D. S., Samper, R. E., King, D. W., King, L. A., & Martin, J. A. (2008). Deployment stressors and posttraumatic stress symptomatology: Comparing active duty and National Guard/Reserve personnel from Gulf War I. Journal of Traumatic Stress, 21, 66 –74. doi:10.1002/jts.20306 Wells, T. S., Jacobson, I. G., Smith, T. C., Spooner, C. N., Smith, B., Reed, R. J., . . . The Millennium Cohort Study Team. (2008). Prior health care utilization as a potential determinant of enrollment in a 21-year prospective study, the Millennium Cohort Study. European Journal of Epidemiology, 23, 79 – 87. doi:10.1007/s10654-007-9216-0 Wells, T. S., LeardMann, C. A., Fortuna, S. O., Smith, B., Smith, T. C., Ryan, M. A., . . . The Millennium Cohort Study Team. (2010). A prospective study of depression following combat deployment in support of the wars in Iraq and Afghanistan. American Journal of Public Health, 100, 90 –99. doi:10.2105/AJPH.2008.155432 Werber, L., Harrel, M. C., Varda, D. M., Hall, K. C., Beckett, M. K., & Stern, S. (2008). Deployment experiences of Guard and Reserve families: Implications for support and retention. Retrieved from http://www.rand.org/pubs/monographs/MG645 Received March 10, 2014 Revision received June 9, 2014 Accepted June 12, 2014 䡲