Thirty-Day Prevalence ofDSM-IVMental Disorders Among Nondeployed Soldiers in the US Army

IMPORTANCE Although high rates of current mental disorder are known to exist in the US Army, little is known about the proportions of these disorders that had onsets prior to enlistment. OBJECTIVE To estimate the proportions of 30-day DSM-IV mental disorders among nondeployed US Army personnel with first onsets prior to enlistment and the extent which role impairments associated with 30-day disorders differ depending on whether the disorders had pre- vs post-enlistment onsets. DESIGN, SETTING, AND PARTICIPANTS A representative sample of 5428 soldiers participating in the Army Study to Assess Risk and Resilience in Servicemembers completed self-administered questionnaires and consented to linkage of questionnaire responses with administrative records. MAIN OUTCOMES AND MEASURES Thirty-day DSM-IV internalizing (major depressive, bipolar, generalized anxiety, panic, and posttraumatic stress) and externalizing (attention-deficit/ hyperactivity, intermittent explosive, alcohol/drug) disorders were assessed with validated self-report scales. Age at onset was assessed retrospectively. Role impairment was assessed with a modified Sheehan Disability Scale. RESULTS A total of 25.1% of respondents met criteria for any 30-day disorder (15.0% internalizing; 18.4% externalizing) and 11.1% for multiple disorders. A total of 76.6% of cases reported pre-enlistment age at onset of at least one 30-day disorder (49.6% internalizing; 81.7% externalizing). Also,

M ental disorders are leading causes of US military morbidity. 1 Indeed, health care visits and days out of role owing to mental disorders in the US military are exceeded only by those owing to injuries. 2 This is partly because selection and retention criteria lead to low rates of chronic physical disorders, but military service also has unique stressors that can increase mental disorders. [3][4][5][6] Annual hospital bed days owing to mental disorders in the US military doubled 7 between 2006 and 2010. The military suicide rate also increased substantially during this period. 8 Although these trends are widely believed to be linked to the protracted conflicts in Afghanistan and Iraq, 3,9 it is not clear how many of these cases represented recurrences of pre-enlistment disorders. This question is important given recent discussions of optimal recruitment-retention strategies for an all-volunteer Army during times of war. 10,11 We know from general population epidemiological studies that most lifetime mental disorders have childhood-adolescence onsets [12][13][14] that are initially too mild to cause rejection from military service, even if they predict more severe subsequent episodes. 15 We are unaware of previous research that has examined the question of pre-enlistment history of mental disorders. Such data are presented here from the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS; www.armystarrs.org), a large multicomponent epidemiological-neurobiological study of Army suicide. 16

The Sample
Data came from the April to December 2011 Army STARRS All-Army Study (AAS), a de-identified cross-sectional survey of active duty soldiers exclusive of those in Basic Combat Training or deployed to a combat theater. Quarterly AAS replicates consisted of stratified (by Army Command location) probability samples of units or subunits selected with probabilities proportional to authorized unit strength excluding units of fewer than 30 soldiers (less than 2% of Army personnel). All personnel in selected units were ordered to attend an informed consent presentation explaining study purposes, confidentiality, and voluntary participation before requesting written informed consent for a group self-administered questionnaire to link their administrative records to questionnaire responses and to participate in future data collections. Identifying information (eg, name and social security number) was collected from consenting respondents and kept in a separate secure file. These recruitment, consent, and data protection procedures were approved by the Human Subjects Committees of the Uniformed Services University of the Health Sciences for the Henry M. Jackson Foundation (the primary grantee), the Institute for Social Research at the University of Michigan (the organization collecting the data), and all other collaborating organizations.
A total of 327 group sessions were held in April to December 2011. Sessions were held with platoons (typically 30-60 soldiers), companies (typically 80-225 soldiers), or other subunits of battalions (typically 300-1300 soldiers, but divided into smaller groups for group administration). The median number of attendees was 18 (range, 1-169; interquartile range [ie, 25th-75th percentiles], . Small sessions were mostly held in medical or military police units to deal with their special 24hour operation schedules. Large sessions were confined to installations with large auditoriums and a short time window for unit data collection. All interview sessions were scheduled for 90 minutes. The 5428 AAS respondents considered here represent all Regular Army soldiers in the April to December 2011 AAS who completed the questionnaire and provided written consent for administrative data linkage. Activated Army Reserve and National Guard respondents were excluded owing to small numbers. Although all unit members were ordered to report to informed consent sessions, 23 17 Although we were prohibited from attempting refusal conversion or obtaining individual-level administrative data for refusers, de-identified administrative data were provided for the entire Army and for survey respondents who agreed to linkage, allowing 2 weights to be created to adjust for nonresponse bias. Weight 1 adjusted for discrepancies in survey responses between survey completers with and without record linkage. Weight 2 adjusted for discrepancies between multivariate administrative record profiles of weighted (weight 1) survey completers with record linkage and the target population. Doubly weighted (weight 1 × weight 2) data were used in analyses. A more detailed description of AAS weighting is presented elsewhere. 18 Measures Data Collection Mode Some data collection staff members were stationed throughout the field period at the largest 6 domestic Army installations (Forts Bliss and Hood in Texas, Bragg in North Carolina, Campbell in Kentucky, Carson in Colorado, and JB Lewis-McChord in Washington; together accounting for 63.5% of the AAS sample). Other staff traveled to smaller installations. Questionnaires were computer-administered using laptop computers at the 6 largest installations, while paper and pencil administration was used at other facilities. A discussion of considerations in this dual-mode approach to data collection is presented elsewhere. 19 Diagnostic Assessment Respondents self-administered the Composite International Diagnostic Interview Screening Scale (CIDI-SC) 20 and the Posttraumatic Stress Disorder (PTSD) Checklist (PCL) 21 to assess 30-day DSM-IV mental disorders. We distinguished between internalizing and externalizing disorders based on empirical evidence for the importance of this distinction. 22 Internalizing disorders included major depressive disorder (MDD), bipolar I and II or subthreshold bipolar disorder, generalized anxiety disorder (GAD), panic disorder (PD), and PTSD. Externalizing disorders included attention-deficit/hyperactivity disorder (ADHD), intermittent explosive disorder (IED), and substance use disorder (SUD; alcohol or drug abuse or dependence). The SUD assessment included both illicit drugs and misused prescription drugs (the latter was defined as use either without a doctor's prescription; more than prescribed; or to get high, buzzed, or numbed out) based on evidence that prescription drug misuse is considerably more common than illicit drug use in the Army. 23 All disorders were assessed without DSM-IV diagnostic hierarchy or organic exclusion rules. Respondents who reported a disorder were asked at what age they first experienced the disorder. Comparison of these age at onset (AAO) reports with respondent age at enlistment was used to distinguish disorders with pre-vs post-enlistment onsets. An AAS clinical reappraisal study found good individuallevel concordance (area under the receiver operating characteristic curve of 0.69-0.79 across diagnoses) 24 between diagnoses based on the CIDI-SC or PCL and independent clinical diagnoses based on blinded administration of the Structured Clinical Interview for DSM-IV. 25 The clinical reappraisal study also found that CIDI-SC and PCL prevalence estimates were unbiased relative to the Structured Clinical Interview for DSM-IV prevalence estimates (χ 2 1 = 0.0-0.6, P = .89 to .43). 24 Health-Related Role Impairment The severity of health-related role impairment was assessed with a revised version of the Sheehan Disability Scale 26 asking respondents the extent to which problems with physical health, mental health, or alcohol-drug use interfered with their functioning in the past 30 days in each of 4 role domains using a 0 to 10 visual analogue scale labeled as no interference (0), mild (1-3), moderate (4-6), severe (7-9), and very severe (10) interference. The 4 domains were home management, quality of work on duty, social life, and close personal relationships. Severe self-reported role impairment was defined as a 7 to 10 rating in 1 or more domains.

Sociodemographic and Army Career Variables
Sociodemographic variables considered here included respondent sex, race/ethnicity, and marital status. Army career variables included rank, age at enlistment, number of deployments to a combat theater, and current Army Command assignment (the major organizational subdivisions within the Army). Race and ethnicity were assessed in 2 questions, the first asking respondents whether they were Spanish, Hispanic, or Latino (yes or no) and the second asking respondents to record their race by checking all applicable categories of white, black or African American, American Indian or Native American, Asian (eg, Chinese, Filipino, or Indian), and Native Hawaiian or other Pacific Islander and/or providing an open-ended response to an other race category. Responses were collapsed into the summary categories of non-Hispanic black, non-Hispanic white, Hispanic, and others. Race and ethnicity were assessed as part of an effort to create a comprehensive sociodemographic profile of soldiers. Distributions of sociodemographic and career variables in the weighted AAS sample are quite comparable with those in the target population ( Table 1).

Analysis Methods
Thirty-day prevalence of disorders with pre-and postenlistment AAO were compared with estimates from a subsample of the National Comorbidity Survey Replication (NCS-R), 27 a US national household survey that assessed DSM-IV disorders with the full CIDI, 20 calibrated to be sociodemographically comparable with the AAS using methods described elsewhere. 28 Predicted age at enlistment was imputed at the individual level to NCS-R respondents using the SAS PROC MI procedure, 29 which implemented Rubin's multiple imputation method 30 using all variables available in both the NCS-R and Army administrative data set to make imputations. Logistic regression analysis was used to examine associations of sociodemographic and Army career variables with disorders and of disorders with self-reported severe role impairment. Coefficients were exponentiated to generate odds ratios (ORs) and 95% CIs. Simulation methods described elsewhere 31 were used to calculate population-attributable risk proportions (PARPs) of severe role impairment owing to 30day DSM-IV disorders with pre-vs post-enlistment AAOs. The PARP describes the proportion of observed severe impairment associated with the predictors. 32 As the AAS data are both clustered and weighted, the design-based Taylor series linearization method was used to estimate standard errors. The significance of predictor sets was evaluated using design-based Wald χ 2 tests. Statistical significance was evaluated using .05level 2-sided tests.
The situation was different for externalizing disorders, where 81.7% of AAS respondents with 30-day prevalence had first onsets of at least 1 such disorder prior to enlistment. None of the disorder-specific proportions with pre-enlistment onset differed significantly in the AAS vs calibrated NCS-R. This means the higher AAS than NCS-R 30-day prevalence estimates of externalizing disorders were owing equally to cases with pre-and post-enlistment onsets.

Sociodemographic and Army Career Predictors of 30-Day Disorder Prevalence
Multivariate logistic regression equations predicted each 30day disorder, any internalizing disorder, any externalizing disorder, and any disorder. Only summary results are presented here ( Table 3). Detailed results are available on request.

Sex
Women soldiers had significantly elevated odds of any internalizing disorder (1.5) and several individual disorders (MDD, GAD, and PTSD; 1.6-2.6).

Race/Ethnicity
Although race and ethnicity are significantly associated overall with any disorder (χ 2 3 = 9.4, P = .02), the only individually significant coefficient was one modestly lower OR among non-Hispanic black than non-Hispanic white individuals (0.7) for IED.

Marital Status
Although the association of marital status with any disorder is nonsignificant, never-married soldiers had significantly lower odds than married soldiers of any externalizing (0.7) disorder owing to significantly lower odds of ADHD and IED (0.5-0.6).

Rank
Rank significantly predicted all disorders, with ORs for lowerrank enlisted soldiers significantly elevated vs officers for each aggregate (2.3-3.5), each internalizing disorder other than MDD (2.2-12.0), and each externalizing disorder (2.7-2.8). In addition, odds for virtually all internalizing disorders other than MDD (2.9-6.5) and all externalizing disorders (2.4-3.0) were significantly higher for higher-rank enlisted soldiers than officers.

Deployment History
Two-thirds of AAS respondents had a history of deployment (31.9% had 1 deployment, 21.1% had 2, and 15.7% had 3 or more).
The number of deployments had a consistently positive monotonic relationship with virtually all disorders and significantly so with 5 (MDD, bipolar disorder, GAD, PTSD, and IED), with ORs in the range of 1.1 to 1.5 for 1, 1.2 to 3.0 for 2, and 1.7 to 3.8 for 3 or more deployments.

Army Command
Current Army Command assignment was significantly associated with any internalizing disorder and several individual disorders owing to elevated odds in the Training and Doctrine Command (GAD and PTSD, 1.3-2.2) and decreased odds in the Special Operations Command (PD and PTSD, 0.3-0.5) compared with the Forces Command.

Associations of 30-Day Disorders With Self-Reported Severe Role Impairment
Reported by 12.8% of respondents, severe role impairment was substantially more common among soldiers with (31.4%) than without (6.6%) DSM-IV mental disorders (χ 2 1 = 79.6, P < .001). Most respondents with self-reported severe role impairment (61.5%) had at least one 30-day DSM-IV disorder. The bestfitting model predicting self-reported severe role impairment distinguishes disorders with pre-vs post-enlistment onsets (χ 2 7 = 16.0, P = .03), with significant ORs generally higher for    the former than latter ( Table 4). Global interactions were significantly subadditive for the number of pre-enlistment (χ 2 2 = 12.6, P = .002) and post-enlistment (χ 2 2 = 6.6, P = .04) onset disorders, meaning that the ORs for comorbid disorders were significantly less than the products of the ORs reported in Table 4 for component disorders.
The PARPs based on the best-fitting model were 21.7% for 30-day disorders with pre-enlistment onsets, 24.3% for 30day disorders with post-enlistment onsets, and 43.4% for all 30-day disorders. The latter estimate was smaller than the sum of the first 2 estimates because the effects of pre-enlistment disorders were partially mediated through post-enlistment dis-

Discussion
Exclusions of deployed soldiers and those in basic training limited generalizability. The low response rate limited external validity despite the lack of evidence of substantial sample bias. 18 In addition, respondents might have underreported mental disorders, 33 although methodological studies show this bias is reduced by using the confidential self-administration procedures used here. 34,35 Within the context of these limitations, AAS 30-day DSM-IV disorders appeared to be more prevalent than among sociodemographically matched civilians owing largely to postenlistment internalizing disorders and both pre-and postenlistment externalizing disorders. The high pre-enlistment externalizing disorders presumably reflected selection processes in the current all-volunteer Army, although the higher prevalence of disorders in the AAS than civilian sample has to be interpreted with caution despite efforts to calibrate the NCS-R owing to incomplete understanding of selection factors into Army service. Inconsistent results have been reported in previous studies attempting to compare civilian and military prevalence estimates using less rigorous calibration methods. 36,37 It is also noteworthy that mental disorders predict early attrition 38 and might influence promotion and deployment, 39 leading to uncertainties in interpreting associations of those variables with disorders.
To our knowledge, although no previous US Army epidemiological survey estimated the prevalence of the same disorders as the AAS, the 25.1% overall 30-day AAS prevalence estimate was close to the 19.5% estimate for a similar set of disorders in the Millennium Cohort Study. 40 It is more difficult to compare disorder-specific AAS prevalence estimates with previous surveys owing to variation in samples and measures, but useful comparisons can be gleaned from 3 recent state-of-the-art reviews on military MDD, 41 PTSD, 42 and SUD. 43 The MDD review found a relatively stable prevalence estimate across 25 US Army surveys, with median prevalence (4.4%) similar to the 4.8% AAS estimate. 41 In comparison, the PTSD review found wide variation in prevalence estimates (2.2%-17.3%) across surveys of Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn servicemembers. 42 The 8.6% AAS PTSD prevalence estimate was at the median of this range, presumably reflecting the AAS inclusion of never-deployed soldiers (who had low PTSD prevalence) and noncoverage of the National Guard and Army Reserve (found in other surveys to have high PTSD prevalence). Finally, the SUD review focused on heavy substance use rather than abuser dependence. 44 Nor did most previous military surveys study bipolar disorder, GAD, PD, ADHD, or IED, despite 2 of these disorders (ADHD and IED) being among the most common disorders considered here.
That most AAS 30-day DSM-IV disorders had preenlistment onsets should not be surprising given early mental disorder AAO in the general population. 13,14 That most 30day internalizing disorders with pre-enlistment onsets had comparable prevalence with calibrated civilian estimates suggests that the high AAS 30-day prevalence of internalizing disorders was largely owing to elevated onset risk after enlistment. The situation is different for externalizing disorders, although where pre-enlistment onset in the AAS is much higher than in the civilian sample, suggesting that early-onset externalizing disorders are associated with joining and/or remaining in the Army. Implications of these findings for recruitment are unclear because the Army already screens for emotional problems in pre-enlistment health examinations. However, knowledge that new recruits have high externalizing disorder rates (even if denied in recruitment interviews) might be useful to the Army in developing targeted outreachintervention programs for new soldiers such as interventions for ADHD 45,46 and for problems with anger management. 47,48 Results from the AAS regarding sociodemographic and Army career predictors are mostly consistent with previous studies in finding higher rates of internalizing disorders among women than men, 49,50 somewhat lower rates of IED among non-Hispanic black than white individuals, 40,51,52 weak associations with age at enlistment, 53,54 strong inverse associa- tions of prevalence with rank, 40,44 and positive associations of prevalence with number of deployments. 55,56 However, 3 of these associations warrant brief comment. First, sex differences in AAS prevalence estimates, consistent with other military surveys, 44 were smaller than in civilian surveys, 49,57-59 possibly reflecting differential selection of women into Army service, narrowing of sex differences in military roles, 60 or sex differences in psychological reactions to military stressors. 61,62 These possibilities deserve further study in light of the increasing role of women in the military.
Second, the finding that never-married soldiers had somewhat lower prevalence than married soldiers 63 and absence of higher prevalence among previously married than married soldiers 64,65 were inconsistent with general-population studies. This might be owing to unique stressors faced by military marriages (frequent moves, deployments, and rules and regulations). 66 Further analysis is needed to investigate this possibility and to determine whether, as with civilians, effects of marriage might differ by sex 67 and be related as much to quality duration as to marriage per se. 68 Third, although the low disorder prevalence in Special Operations Command was broadly consistent with evidence of hyperresilience to stress among Special Operations soldiers, 69,70 the ethic of stoicism in Special Operations culture 71 might have led Special Operations survey respondents to underreport emotional problems. 55 In comparison, we are unaware of previous research that documented elevated mental disorder prevalence in Training and Doctrine Command.
Finally, the finding that 30-day DSM-IV disorders were strong predictors of self-reported severe role impairments was broadly consistent with evidence that mental disorders are highly impairing. 72,73 The 43.4% PARP is considerably higher than in civilian surveys, although presumably reflecting Army recruitment-retention practices that reduce impairing physical disorders. That PARP is higher for pre-enlistment than postenlistment mental disorders is consistent with evidence that early AAO is associated with increased mental disorder severity. 74,75 Conclusions Although we know of no previous studies of pre-vs postenlistment disorders, evidence exists for associations of childhood stresses 76 and mental disorders 77,78 with poor soldier functioning, lending indirect support to the results reported here. It would be possible to expand future recruitment screening efforts to include self-reports about these pre-enlistment risk factors, but the inability to obtain objective confirmation of these self-reports could undercut the value of such efforts. Another possibility would be to build outreach and treatment programs for new soldiers based on these research findings aimed at attracting soldiers with known pre-enlistment risk factors for targeted interventions, with pre-enlistment mental disorders included in this set of risk factors.