Associations of Time-Related Deployment Variables With Risk of Suicide Attempt Among Soldiers

Key Points

Question

Are time-related deployment variables associated with subsequent risk of suicide attempt among US Army enlisted soldiers?

Findings

This longitudinal cohort study of soldiers who deployed exactly twice examined administrative records from 593 medically documented suicide attempters and 19 034 control person-months. Risk of suicide attempt during or after second deployment was higher for those who initially deployed within the first 12 months of service and those with a dwell time (length of time between deployments) of 6 months or less.

Meaning

Time in service before first deployment and dwell time are modifiable risk factors for suicide attempts among soldiers.

Abstract

Importance

There has been limited systematic examination of whether risk of suicide attempt (SA) among US Army soldiers is associated with time-related deployment variables, such as time in service before first deployment, duration of first deployment, and dwell time (DT) (ie, length of time between deployments).

Objective

To examine the associations of time-related deployment variables with subsequent SA among soldiers who had deployed twice.

Design, Setting, and Participants

Using administrative data from January 1, 2004, through December 31, 2009, this longitudinal, retrospective cohort study identified person-month records of active-duty Regular Army enlisted soldiers who had served continuously in the US Army for at least 2 years and deployed exactly twice. The dates of analysis were March 1 to December 1, 2017. There were 593 soldiers with a medically documented SA during or after their second deployment. An equal-probability sample of control person-months was selected from other soldiers with exactly 2 deployments (n = 19 034). Logistic regression analyses examined the associations of time in service before first deployment, duration of first deployment, and DT with subsequent SA.

Main Outcomes and Measures

Suicide attempts during or after second deployment were identified using US Department of Defense Suicide Event Report records and International Classification of Diseases, Ninth Revision, Clinical Modification E950 to E958 diagnostic codes. Independent variables were constructed from US Army personnel records.

Results

Among 593 SA cases, most were male (513 [86.5%]), white non-Hispanic (392 [66.1%]), at least high school educated (477 [80.4%]), currently married (398 [67.1%]), and younger than 21 years when they entered the US Army (384 [64.8%]). In multivariable models adjusting for sociodemographics, service-related characteristics, and previous mental health diagnosis, odds of SA during or after second deployment were higher among soldiers whose first deployment occurred within the first 12 months of service vs after 12 months (odds ratio, 2.0; 95% CI, 1.6-2.4) and among those with a DT of 6 months or less vs longer than 6 months (odds ratio, 1.6; 95% CI, 1.2-2.0). Duration of first deployment was not associated with subsequent SA. Analysis of 2-way interactions indicated that the associations of early deployment and DT with SA risk were not modified by other characteristics. Multivariable population-attributable risk proportions were 14.2% for deployment within the first 12 months of service and 4.0% for DT of 6 months or less.

Conclusions and Relevance

Time in service before first deployment and DT are modifiable risk factors for SA risk among soldiers.

This longitudinal cohort study examines the associations of time-related deployment variables with subsequent suicide attempt among soldiers who had deployed twice.

Introduction

Rates of suicidal behaviors, including suicide deaths, attempts, and ideation, among US Army soldiers increased considerably during the wars in Iraq and Afghanistan.^1,2 Findings regarding the association between deployment history and suicidal behaviors are mixed,^{2,3,4,5,6,7,8,9} suggesting that these relationships are complex. Time-related deployment variables, such as time in service before first deployment, duration of first deployment, and length of time between deployments for recovery, retraining, and reset (ie, dwell time [DT]), may affect mental health^10,11,12,13 but have received little attention in studies of military suicide risk. Understanding time-related factors has implications for managing human resources during combat and predicting suicidal behavior in other high-risk occupations.

Perceived preparedness for deployment is associated with more positive mental health outcomes.^14,15,16 Therefore, soldiers whose first deployment occurs early in their career could be at elevated risk for suicidal behavior. Risk may be particularly high for those who deploy within the first year of service, a time of initial training and US Army acculturation. This adjustment period is difficult for some soldiers, as evidenced by the greatly elevated risk of suicide attempt (SA) among soldiers in their first year.⁸ To our knowledge, only one study⁴ has examined time in service before first deployment as a risk factor for suicidal behavior, finding that currently deployed enlisted soldiers who were in their first year of service had substantially elevated risk of dying by suicide. However, it is not known how deployment within the first year may affect longer-term risk of suicidal behavior during or after subsequent deployments.

Duration of first deployment is another potentially important factor in understanding suicide risk.^17,18 Longer deployments may increase exposure to deployment-related stressors, such as combat, separation from family, and boredom.¹⁹ There is evidence indicating that greater deployment length is associated with adverse mental, physical, and interpersonal consequences,²⁰ but this finding is somewhat inconsistent.^12,21,22 Furthermore, previous studies often focused on cumulative deployment time over a servicemember’s career, which does not specifically address the risk associated with the length of individual deployments.

Dwell time allows servicemembers to recover mentally and physically from previous deployments and prepare for upcoming deployments through additional training.²³ Longer DT among soldiers and US Marine Corps members has been associated with decreased odds of mental health problems (eg, posttraumatic stress disorder and depression) and decreased odds of referral for mental health services.^13,24,25 Conversely, a study²⁶ that included all US military services found that longer DT was related to increased risk of mental health diagnosis, although that study did not account for important differences between military branches, including deployment experiences.

This study used administrative data from the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS)²⁷ to examine the associations of time-related deployment variables (time in service before first deployment, duration of first deployment, and DT) with subsequent risk of SA among Regular Army enlisted soldiers during or after their second deployment. These analyses were conducted before and after adjusting for basic sociodemographic characteristics, other service-related variables, and history of mental health diagnosis. We also investigated whether the associations of time-related deployment variables with SA were modified by each other or by sex, deployment status (currently vs previously deployed), history of mental health diagnosis, or combat occupation.

Methods

Sample

This longitudinal, retrospective cohort study used data from the Army STARRS Historical Administrative Data Study (HADS), which integrates 38 US Army and Department of Defense (DoD) administrative data systems, including every system in which suicidal events are medically documented. The HADS includes individual-level person-month records for all soldiers on active duty between January 1, 2004, and December 31, 2009 (1.66 million).²⁸ This component of the Army STARRS was approved by the institutional review boards of the Uniformed Services University of the Health Sciences, Harvard Medical School, University of California San Diego, and University of Michigan Institute for Social Research, which determined that the present study did not constitute human participant research because it relies entirely on deidentified secondary data. The dates of analysis were March 1 to December 1, 2017.

The HADS contains administrative records for the 975 057 Regular Army soldiers on active duty during the study period (excluding activated US Army National Guard and Army Reserve), including 9791 who had a documented SA. This study focused on enlisted soldiers, who accounted for almost 99% of Regular Army SAs from 2004 through 2009, with officers accounting for the other 1%.⁸ Soldiers were included in the sample if they had served continuously since entering the US Army and had deployed exactly twice (ie, currently deployed soldiers on their second deployment and previously deployed soldiers who had returned from their second deployment). Soldiers with more than 2 deployments were excluded, as were those with less than 2 years of service, because it is not typical to have 2 deployments within this short time frame. The study also excluded 2085 soldiers whose first or second deployment was longer than 24 months. Special Forces were excluded owing to their frequent, atypical deployment schedule. The final analytic sample included all 593 soldiers whose first administratively recorded SA was during or after their second deployment and a 1:200 equal-probability sample of control person-months (n = 19 034) that were selected after stratifying the population of enlisted soldiers by sex, rank, time in service, deployment status (currently or previously deployed), and historical time. Control person-months excluded all soldiers with a documented SA or other nonfatal suicidal event (eg, suicidal ideation)¹ and person-months in which a soldier died. Data were analyzed using a discrete-time survival framework with person-month as the unit of analysis,²⁹ such that each month in the career of a soldier was treated as a separate observational record. Each control person-month was assigned a weight of 200 to adjust for undersampling.

Measures

Suicide Attempt

Soldiers who attempted suicide were identified using US Army and DoD administrative records from the US Department of Defense Suicide Event Report (DoDSER),³⁰ which is a DoD-wide surveillance mechanism that aggregates information on suicidal behaviors via a standardized form completed by medical providers at DoD treatment facilities. They were also identified using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnostic codes E950 to E958 (indicating self-inflicted poisoning or injury with suicidal intent) from the Military Health System Data Repository, Theater Medical Data Store, and TRANSCOM (Transportation Command) Regulating and Command and Control Evacuating System. Together, these data systems provide health care encounter information from military and civilian treatment facilities, combat operations, and aeromedical evacuations (eTable 1 in the Supplement). We excluded suicide deaths and DoDSER records indicating only suicide ideation. The E959 code (late effects of a self-inflicted injury) was excluded because it confounds the temporal relationships between predictor variables and SA.³¹ Records from different data systems were cross-referenced to ensure that all cases represented unique soldiers. For soldiers with multiple SAs, we selected the first attempt using a hierarchical classification scheme that prioritized DoDSER records (additional details are available elsewhere¹).

Sociodemographic and Service-Related Characteristics

Sociodemographic characteristics (sex, race/ethnicity, educational level, and marital status) and service-related variables (age at US Army entry and deployment status [ie, currently vs previously deployed after second deployment]) were drawn from US Army and DoD administrative data. Also drawn from this source was military occupational specialty (MOS) (combat arms vs other for men only based on duty MOS). Details are listed in eTable 1 in the Supplement.

Time-Related Deployment Variables

Administrative records were used to calculate continuous time-related deployment variables. These included time in service before first deployment, duration of first deployment (range, 1 to >13 months), and DT between the end of the first deployment and the beginning of the second deployment (range, 2 to >36 months).

Previous Mental Health Diagnosis

We created an indicator variable for any mental health diagnosis during US Army service before second deployment by combining categories derived from administrative medical record ICD-9-CM codes (eg, major depression, bipolar disorder, posttraumatic stress disorder, and personality disorders), excluding postconcussion syndrome, tobacco use disorder, and supplemental V-codes that are not disorders (eg, stressors and adversities and marital problems). Details are listed in eTable 2 in the Supplement.

Statistical Analysis

All analyses were conducted using statistical software (SAS, version 9.4; SAS Institute Inc).³² After examining the time-related deployment variables (time in service before first deployment, duration of first deployment, and DT) as continuous predictors of SA in univariable logistic regression models, we graphed significant associations by converting odds to probabilities (suicide attempters per 100 000 person-years). We then transformed the functional form of bivariate associations involving these continuous predictors to capture substantively plausible nonlinearities. The associations of the resulting categorical time-related deployment variables with SA were then examined in univariable and multivariable logistic regression analyses. Multivariable models included the time-related deployment variables, sociodemographic characteristics (sex, race/ethnicity, educational level, and marital status), service-related characteristics (age at US Army entry and deployment status), and previous mental health diagnosis before second deployment. We separately examined 2-way interactions of the time-related deployment variables with each other and with sex, deployment status, and previous mental health diagnosis before second deployment to determine whether the associations of time-related deployment variables with SA were modified by other characteristics. Parameter estimates for the continuous time-related deployment variables are reported as logits. Logistic regression coefficients for categorical predictors were exponentiated to obtain odds ratios (ORs) and 95% CIs. All univariable and multivariable logistic regression models included a dummy predictor for calendar month and year to control for increasing rates of SA during the study period (2004-2009).¹ Coefficients of other predictors can consequently be interpreted as averaged within-month associations based on the assumption that the associations of other predictors do not vary over time. Significance was evaluated using 0.05-level 2-sided tests. Population-attributable risk proportions (PARPs)³³ were calculated to identify the proportions of observed SAs that would not have occurred if significant time-related variables were reduced to reference levels, assuming that coefficients in each model represent causal associations of the predictors. Significance was evaluated using 0.05-level 2-sided tests.

Results

Among 593 SA cases, most were male (513 [86.5%]), white non-Hispanic (392 [66.1%]), at least high school educated (477 [80.4%]), currently married (398 [67.1%]), and younger than 21 years when they entered the US Army (384 [64.8%]) (Table 1). Almost 27% (159 of 593) were currently deployed, and 47.0% (279 of 593) had received a previous mental health diagnosis before second deployment. Most SA cases (71.5% [424 of 593]) deployed for the first time after at least 13 months of service, and slightly more than half (55.5% [329 of 593]) had a first deployment of 9 months or more. The mean (SD) DT was 17.1 (8.5) months (median, 17.0 months), with DT of longer than 6 months for 86.8% (515 of 593) and longer than 12 months for 67.8% (402 of 593).

Table 1. Sociodemographic and Service-Related Characteristics Among Regular Army Enlisted Soldiers Who Deployed Twice^a.

Variable	Unweighted No.		Weighted No.
	Suicide Attempt Cases (n = 593)	Control Person-Months (n = 19 034)	Total Person-Months	Total Proportion
Sociodemographic Characteristics
Sex
Male	513	17 351	3 470 713	91.2
Female	80	1683	336 680	8.8
Race/ethnicity
White non-Hispanic	392	10 726	2 145 592	56.4
Other	201	8308	1 661 801	43.6
Educational level
<High schoolb	116	1641	328 316	8.6
≥High school	477	17 393	3 479 077	91.4
Marital status
Never or previously married	195	6009	1 201 995	31.6
Currently married	398	13 025	2 605 398	68.4
Service-Related Characteristics
Age at US Army entry, y
<21	384	12 317	2 463 784	64.7
21-24	144	4491	898 344	23.6
≥25	65	2226	445 265	11.7
Deployment status
Currently deployed	159	7893	1 578 759	41.5
Previously deployed	434	11 141	2 228 634	58.5
Mental Health Characteristics
Previous mental health diagnosis before second deployment
No	314	14 871	2 974 514	78.1
Yes	279	4163	832 879	21.9
Time-Related Deployment Variables
Time in service before first deployment, mo
≤12	169	3283	656 600	17.2
>12	424	15 751	3 150 200	82.8
Duration of first deployment, mo
≤4	124	4720	944 124	24.8
5-8	140	4625	925 140	24.3
9-12	263	7677	1 535 663	40.3
≥13	66	2012	402 466	10.6
Dwell time, mo
≤6	78	2056	411 278	10.8
7-12	113	3984	796 913	20.9
13-18	175	5434	1 086 975	28.5
19-24	141	4409	881 941	23.2
25-30	39	1244	248 839	6.5
≥31	47	1907	381 447	10.0

^aThe sample of enlisted soldiers with exactly 2 deployments (593 cases and 19 034 control person-months) is a subset of the total sample (193 617 person-months) from the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS) Historical Administrative Data Study (HADS), which includes all Regular Army soldiers (ie, excluding those in the US Army National Guard and Army Reserve) with a suicide attempt in their administrative records during 2004 to 2009, plus a 1:200 stratified probability sample of all other active-duty Regular Army person-months in the population exclusive of soldiers with a suicide attempt or other nonfatal suicidal event (eg, suicidal ideation) and person-months associated with death (ie, suicides, combat deaths, homicides, and deaths due to other injuries or illnesses). All records in the 1:200 sample were assigned a weight of 200 to adjust for the undersampling of months not associated with suicide attempt.

^bLess than high school includes General Educational Development (GED) credential, home study diploma, occupational program certificate, correspondence school diploma, high school certificate of attendance, adult education diploma, and other nontraditional high school credentials.

As continuous predictors, time in service before first deployment (logit, −0.01; P < .001) and DT (logit, −0.02; P < .001) had negative univariable associations with SA during or after second deployment, indicating that SA risk increased as time in service before first deployment and DT decreased (Figure 1 and Figure 2). Duration of first deployment was not associated with subsequent SA. Time in service before first deployment was dichotomized (≤12 vs >12 months) based on its functional form and the rationale that the first year of service is an important period of initial training and US Army acculturation. In a univariable model, soldiers who deployed within the first 12 months of service were almost twice as likely to attempt suicide as those who deployed later (OR, 1.9; 95% CI, 1.6-2.2) (Table 2). To better examine the functional form of DT and its association with SA risk, we created discrete categories by 6-month intervals ranging from 0 to 36 months. In a univariable model, all DT categories greater than 6 months were associated with decreased SA risk compared with DT of 6 months or less (χ²₅ = 20.2; OR range, 0.4-0.7) (eTable 3 in the Supplement). Pairwise analyses indicated no differences between discrete DT categories greater than 6 months; therefore, we dichotomized the DT variable (≤6 vs >6 months). In a univariable model, DT of 6 months or less was associated with increased odds of subsequent SA relative to longer DT (OR, 1.6; 95% CI, 1.2-2.0) (Table 2).

Figure 1. Association of Time in Service Before First Deployment With Suicide Attempt During or After Second Deployment Among Regular Army Enlisted Soldiers Who Deployed Twice.

The sample of enlisted soldiers with exactly 2 deployments (593 cases and 19 034 control person-months) is a subset of the total sample (193 617 person-months) from the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS) Historical Administrative Data Study (HADS), which includes all Regular Army soldiers. Risk of subsequent suicide attempt (per 100 000 person-years) was calculated based on predicted probabilities from a logistic regression model that included time in service before first deployment and a dummy predictor variable for calendar month and year to control for secular trends.

Figure 2. Association of Dwell Time With Suicide Attempt During or After Second Deployment Among Regular Army Enlisted Soldiers Who Deployed Twice.

The sample of enlisted soldiers with exactly 2 deployments (593 cases and 19 034 control person-months) is a subset of the total sample (193 617 person-months) from the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS) Historical Administrative Data Study (HADS), which includes all Regular Army soldiers. Risk of subsequent suicide attempt (per 100 000 person-years) was calculated based on predicted probabilities from a logistic regression model that included dwell time and a dummy predictor variable for calendar month and year to control for secular trends.

Table 2. Univariable and Multivariable Associations of Time-Related Deployment Variables With Suicide Attempt During or After Second Deployment Among Regular Army Enlisted Soldiers Who Deployed Twice^a.

Variable	Odds Ratio (95% CI)
	Univariableb	Multivariable 1c	Multivariable 2d
Sex
Male	1 [Reference]	1 [Reference]	1 [Reference]
Female	1.6 (1.3-2.0)	2.0 (1.5-2.6)	1.6 (1.3-2.0)
χ21	15.0	28.4	13.7
P value	<.001	<.001	<.001
Race/ethnicity
White non-Hispanic	1 [Reference]	1 [Reference]	1 [Reference]
Other	0.7 (0.6-0.8)	0.7 (0.6-0.8)	0.7 (0.6-0.8)
χ21	22.6	18.5	15.0
P value	<.001	<.001	NA
Educational level
<High schoole	2.6 (2.1-3.2)	2.4 (1.9-3.0)	2.2 (1.8-2.8)
≥High school	1 [Reference]	1 [Reference]	1 [Reference]
χ21	83.9	66.5	57.0
P value	<.001	<.001	<.001
Marital status
Never or previously married	1.1 (0.9-1.3)	1.0 (0.8-1.1)	1.0 (0.9-1.2)
Currently married	1 [Reference]	1 [Reference]	1 [Reference]
χ21	1.4	0.3	0.0
P value	.24	.61	.85
Age at US Army entry, y
<21	1 (0.8-1.2)	1 (0.9-1.3)	1 (0.9-1.3)
21-24	1 [Reference]	1 [Reference]	1 [Reference]
≥25	0.9 (0.7-1.2)	0.9 (0.7-1.2)	0.9 (0.7-1.2)
χ22	0.5	0.8	1.0
P value	.79	.67	.61
Deployment status
Currently deployed	1 [Reference]	NA	1 [Reference]
Previously deployed	1.9 (1.6-2.2)	NA	2.1 (1.7-2.6)
χ21	43.6	NA	58.8
P value	<.001	NA	<.001
Previous mental health diagnosis before second deployment
No	1 [Reference]	NA	1 [Reference]
Yes	3.0 (2.6-3.6)	NA	3.1 (2.6-3.6)
χ21	179.4	NA	174.8
P value	<.001	NA	<.001
Time in service before first deployment, mo
≤12	1.9 (1.6-2.2)	1.7 (1.5-2.0)	2.0 (1.6-2.4)
>12	1 [Reference]	1 [Reference]	1 [Reference]
χ21	49.5	35.8	51.1
P value	<.001	<.001	<.001
Duration of first deployment, mo
≤4	1 [Reference]	1 [Reference]	1 [Reference]
5-8	1.2 (0.9-1.5)	1.2 (0.9-1.5)	1.1 (0.9-1.5)
9-12	1.1 (0.9-1.4)	1.2 (1.0-1.5)	1.3 (1.1-1.6)
≥13	1.1 (0.8-1.4)	1.1 (0.8-16.0)	1.4 (1.0-1.9)
χ23	1.9	3.2	6.6
P value	.60	.36	.08
Dwell time, mo
≤6	1.6 (1.2-2.0)	1.8 (1.4-2.2)	1.6 (1.2-2.0)
>6	1 [Reference]	1 [Reference]	1 [Reference]
χ21	12.9	17.5	11.1
P value	<.001	<.001	<.001

Abbreviation: NA, not applicable.

^aThe sample of enlisted soldiers with exactly 2 deployments (593 cases and 19 034 control person-months) is a subset of the total sample (193 617 person-months) from the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS) Historical Administrative Data Study (HADS), which includes all Regular Army soldiers (ie, excluding those in the US Army National Guard and Army Reserve) with a suicide attempt in their administrative records during 2004 to 2009, plus a 1:200 stratified probability sample of all other active-duty Regular Army person-months in the population exclusive of soldiers with a suicide attempt or other nonfatal suicidal event (eg, suicidal ideation) and person-months associated with death (ie, suicides, combat deaths, homicides, and deaths due to other injuries or illnesses). All records in the 1:200 sample were assigned a weight of 200 to adjust for the undersampling of months not associated with suicide attempt.

^bEach predictor was examined in a separate univariable logistic regression model that also included a dummy predictor variable for calendar month and year to control for secular trends.

^cMultivariable 1 is logistic regression that included sociodemographic characteristics (sex, race/ethnicity, educational level, and marital status), age at US Army entry, time in service before first deployment, duration of first deployment, dwell time, and a dummy predictor variable for calendar month and year to control for secular trends.

^dMultivariable 2 is logistic regression that included all variables in the multivariable 1 model plus deployment status and previous mental health diagnosis before second deployment.

^eLess than high school includes General Educational Development (GED) credential, home study diploma, occupational program certificate, correspondence school diploma, high school certificate of attendance, adult education diploma, and other nontraditional high school credentials.

These results persisted when the time-related deployment variables were examined together in a multivariable model that adjusted for sociodemographic and service-related characteristics. Odds of SA were higher among soldiers with 12 months or less of service before first deployment (χ²₁ = 35.8; OR, 1.7; 95% CI, 1.5-2.0) and DT of 6 months or less (χ²₁ = 17.5; OR, 1.8; 95% CI, 1.4-2.2). We further tested the robustness of these findings by adding deployment status (currently vs previously deployed) and mental health diagnosis before second deployment. Notably, deployment within the first 12 months of service (χ²₁ = 51.1; OR, 2.0; 95% CI, 1.6-2.4) and DT of 6 months or less (χ²₁ = 11.1; OR, 1.6; 95% CI, 1.2-2.0) remained significant. The 2-way interaction between time in service before first deployment and DT was nonsignificant when examined in a multivariable model adjusting for all other predictors. The 2-way interactions between each of those predictors and sex, deployment status, previous mental health diagnosis, and duration of first deployment were also nonsignificant.

To examine whether combat vs noncombat MOS modified the associations of early first deployment and DT with SA, we first stratified by sex and then added MOS to the full multivariable model among men (women were not in combat arms at that time) (eTable 4 in the Supplement). Even after adjusting for MOS, SA risk remained higher for men who deployed within the first 12 months of service (OR, 1.9; 95% CI, 1.6-2.3) or had DT of 6 months or less (OR, 1.6; 95% CI, 1.2-2.1) (eTable 5 in the Supplement). When 2-way interactions were examined in separate multivariable models, the associations of early deployment and DT with SA among men did not differ by MOS.

The PARP for deploying within the first 12 months of service (based on the full multivariable model, including deployment status and previous mental health diagnosis before second deployment) was 14.2%, suggesting that SAs might be reduced by as much as 14.2% if all soldiers with 2 deployments served for more than 12 months before their first deployment. The PARP for DT of 6 months less (based on the same multivariable model) was 4.0%, indicating that SAs might be reduced by as much as 4.0% if DT for all soldiers with 2 deployments was greater than 6 months.

Discussion

Among soldiers with exactly 2 deployments, those who served 12 or fewer months before their first deployment were approximately twice as likely to attempt suicide during or after their second deployment compared with those who had more time to train and acclimate to the military before initial deployment. Risk of SA increased as DT decreased, highlighting that this period of rest, recovery, and preparation between deployments has an important protective role. These associations persisted even after adjusting for other time-related deployment variables and factors that have previously been associated with SA and suicide death in active-duty military personnel and veterans, including sociodemographic and service-related characteristics, deployment status, and previous mental health diagnosis before second deployment.^{1,5,7,8,34,35,36,37} The associations of early first deployment and DT with SA risk were not modified by each other or by sex, deployment status, previous mental health diagnosis, or duration of first deployment. While it is notable that duration of first deployment was not associated with SA risk during or after second deployment, it will be important to examine this question among soldiers who have deployed only once.

Soldiers may experience short-term readjustment responses, including insomnia, irritability, and difficulty concentrating, as they transition home between deployments.^38,39 To address these issues and the challenges experienced as soldiers and veterans reunite with family and reintegrate into life at home,^40,41 longer DT may provide additional opportunity for readjustment and preparation for subsequent deployment. For soldiers exposed to significant combat and deployment stressors, DT may be a key period during which to address the influence of these experiences. Research among deployed soldiers indicates that 30 to 36 months of DT is associated with decreased rates of mental health problems (acute stress, anxiety, and depression) comparable to rates of soldiers in garrison.¹³ Our findings suggest that the critical DT for reducing SA risk is longer than 6 months. The beneficial associations of DT may well vary across outcomes. Notably, a previous study⁴ found no association between DT and suicide death, but those findings were based on the most recent DT among all soldiers with multiple deployments. It is important for future studies to examine the association of DT with different suicidal outcomes using comparable samples.

The risks associated with time-related deployment variables were similar among men with combat arms vs other occupations. Although this finding might suggest that combat exposure does not alter the risk associated with early deployment or shorter DT, better measures of combat exposure will be required to draw such conclusions. It is also important to examine time-related variables among other occupations with elevated SA risk, particularly combat medics.³⁷

Our findings indicate that SAs among soldiers during or after their second deployment might be reduced by as much as 14.2% if all soldiers were in the US Army for more than 1 year before first deployment. Dwell time of longer than 6 months for all soldiers could result in a modest 4.0% reduction in SAs among those who have deployed twice. These findings suggest that personnel management—reflecting training, acculturation, rest, and recovery—is an important aspect of SA risk in the US Army.

Limitations

Several limitations should be considered in the interpretation of these findings. Administrative data may be incomplete or inaccurate. Suicide attempt and mental health records are unlikely to capture all cases, and they are subject to errors in clinician diagnosis and administrative or medical coding. These findings may not generalize to earlier and later periods of the wars in Iraq and Afghanistan or to other US military conflicts. Our findings may not generalize to officers, the US Army National Guard, Army Reserve, or veterans separated from the US Army. We plan to include these populations in future Army STARRS analyses. Notably, our results may have been affected by our requirement that soldiers had exactly 2 deployments because the composition of this group is likely affected by the nonrandom nature of US Army attrition and deployment.^42,43,44 Future studies should consider time-related deployment variables among soldiers with fewer or more deployments and among those who have separated from the US Army.

Conclusions

Early first deployment and shorter DT were associated with elevated risk of SA among enlisted soldiers with 2 deployments regardless of sociodemographic characteristics, other service-related variables, or previous mental health diagnosis before second deployment. These time-related deployment variables are potentially modifiable risk factors for SA, contingent on the operational requirements of the wartime environment. Further consideration should be given to how well the timing of first deployment corresponds with the US Army’s training and preparedness goals for new soldiers. The continued focus of the US Army on DT may help mitigate a range of negative outcomes and reduce risk of suicidal behavior. Future research that examines factors associated with DT, including type and extent of social support at home, training and reset opportunities, parenting and household responsibilities and challenges, and family and financial stressors, would provide a better understanding of the association between this period and SA risk.

Supplement.

eTable 1. List and Brief Descriptions of Administrative Data Systems Included in the 2004-2009 Army STARRS Historical Administrative Data Study (HADS)

eTable 2. International Classification of Diseases, Ninth Revision–Clinical Modification (ICD-9-CM) Codes Used to Identify Mental Disorders

eTable 3. Univariable and Multivariable Associations of Time-Related Deployment Characteristics With Suicide Attempt During or After Second Deployment Among Regular Army Enlisted Soldiers Who Deployed Twice

eTable 4. Sociodemographic and Service-Related Characteristics Among Male Regular Army Enlisted Soldiers Who Deployed Twice

eTable 5. Multivariable Associations of Time-Related Deployment Characteristics With Suicide Attempt During or After Second Deployment Among Male Regular Army Enlisted Soldiers Who Deployed Twice