More than a quarter (25.6%) of those on a combat deployment in the past year reported frequent binge drinking. Compared with those who do not binge drink on a weekly basis, frequent binge drinkers were more likely to be men, to be in the youngest age range (17-25 years), white, single (never married or divorced/separated), and have a high school education or less. In terms of military characteristics, frequent binge drinkers compared with others were more likely to be in the Army or Marine Corps, have a junior (E1-E6) pay grade, and have high lifetime combat exposure. In terms of clinical characteristics, frequent binge drinkers were more likely than others to have a positive screen for current PTSD, past year depression, and report suicidal ideation in the past year.
Among the study sample, 39.3% reported being exposed to at least 1 injury event on the most recent combat deployment. These events were postcoded as a blast/explosion, “other” injury etiology (eg, vehicular accident/crash, fragment or bullet wound above the shoulders, fall), or both blast and other event (see Table 2). Most common was the report of experiencing both a blast and other injury etiology (19.8%) during the most recent combat deployment, with similar proportions experiencing blast only (9.7%) or other injury etiologies only (9.8%). In total, almost one-third (29.5%) of the study sample had experienced a blast. We could not determine whether personnel experienced 1 or more injury events.
Overall, 13.9% of the study population reported experiencing a TBI after an injury exposure during their most recent deployment. The most common type of TBI was TBI-AC (7.5%), followed by TBI-LOC <1 (3.5%), and TBI-LOC 1+ (2.8%). Proportions at each TBI level varied by the type of injury event exposure (see Table 2). The highest rate of self-reported TBI (49.3%) was among those personnel who experienced both a blast and other injury etiology. Those with a blast exposure only reported the lowest rate of each TBI level. Almost 15% of men reported a TBI, whereas only 4.9% of women did so (data not shown). There was a dose-response relation between both TBI and PTSD and TBI and depression. For example, the relation between TBI and PTSD revealed that among those with TBI-AC, 26.8% had a positive PTSD screen, 41.5% of those with TBI-LOC <1 reported PTSD, and 59.7% of those with TBI-LOC 1+ had a positive PTSD screen (data not shown).
Table 3 presents the unadjusted and adjusted association of TBI with the probability of frequent binge drinking. Unadjusted analyses showed that military personnel with a TBI were significantly more likely to report frequent binge drinking in the past month than those without a TBI. As TBI severity increased, the odds of frequent binge drinking also increased in a dose-response relation. Model 2 showed that when controlling for demographic characteristics and combat exposure, the AORs for each TBI level decreased slightly but remained significant.
In all 3 adjusted models, several demographic and combat exposure variables were significantly associated with frequent binge drinking. Men had higher odds of frequent binge drinking than women. Those in the Air Force had lower odds of frequent binge drinking than those in the Army, but those in the other branches were not significantly different from those in the Army. Military personnel who identified as black or “other” race/ethnicity had lower odds of frequent binge drinking than white personnel. Those married or living as married had lower odds of frequent binge drinking than those who had never been married. Military personnel at the E7-E9 pay grade, warrant officers, and commissioned officers all had lower odds of frequent binge drinking than those at the lowest pay grades (E1-E6). And, those with high lifetime combat exposure had higher odds of frequent binge drinking than those with no lifetime combat exposure.
In model 3a, a positive screen for PTSD had a significant association with frequent binge drinking, yet 2 levels of combat-acquired TBI remained significantly associated as well. Those with a TBI-AC had increased odds of frequent binge drinking, as did TBI-LOC 1+. In model 3B, both a positive depression screen and suicidal ideation in the past year were significantly associated with frequent binge drinking; however, once again, TBI-AC and TBI-LOC 1+ remained significantly associated with frequent binge drinking, although the AORs were attenuated and smaller than observed when PTSD was the covariate.
When we conducted sensitivity analyses after dropping 89 cases with an LOC of greater than 20 minutes, the coefficient for those with TBI-LOC 1+ was only slightly smaller (AOR, 1.25; 95% CI, 0.69-2.27) and was not statistically significant (P = .45), which may be related to a substantially smaller TBI-LOC 1+ group (data not shown).
There are significant costs of frequent binge drinking among returning active duty military personnel. Drinking at unhealthy levels may interfere with reintegration and complicate other combat-related injuries and conditions. More than a quarter (25.6%) of military personnel who had been on a combat deployment in the past year reported frequent binge drinking, placing themselves at very high risk of negative drinking consequences such as poor job performance and alcohol-impaired driving,13,19 which may compromise their readiness for a subsequent deployment. Multivariate analyses indicated that those personnel with a TBI during their most recent combat deployment were more likely to be frequent binge drinkers than those without TBI, controlling for demographics, lifetime combat exposure, and comorbidity. Although we cannot draw causal inferences from this cross-sectional analysis, our findings suggest that experiencing a TBI is one driver of unhealthy drinking postdeployment.
Military personnel with a positive PTSD screen had higher odds of frequent binge drinking than those without a positive screen. The findings also suggest that PTSD may partially mediate the relation between TBI and frequent binge drinking. When PTSD was added, the AORs for all TBI level variables decreased from model 2. Although reduced in magnitude, TBI-AC and TBI-LOC 1+ remained significant. Thus, TBI has an apparent independent relation to frequent binge drinking.
Importantly, this study also demonstrates that TBI-AC increased the likelihood of frequent binge drinking in all models. The dose-response relation between TBI and frequent binge drinking apparent in the unadjusted model 1 was not as evident in models 2 and 3. However, the most severe TBI (TBI-LOC 1+) retained the highest AOR in all models. We can only speculate at this time about the diminution in dose-response relation of TBI level and frequent binge drinking in models 2 and 3. It may be an artifact of sample size, or more severe injury may be protective because of unknown mediating factors (eg, more likely to be on a prescription medication for symptom relief; more likely to have been advised not to drink to excess). There was also confounding of TBI level and positive PTSD screen, and the TBI-AC participants had the lowest proportion of positive PTSD screens. Finally, improved measurement of type of injury, particularly among those exposed to blasts, may provide additional, useful information about the nature of the TBI. Future studies could examine whether there are other injury characteristics associated with drinking behavior.
Almost 40% of the sample reported at least 1 injury event exposure during the deployment that ended in the past year, and 13.9% reported symptoms of TBI while on this recent deployment. This overall prevalence is within the range of estimates from previous US studies, which have reported a rate from 12% to almost 23%.20–22,26,48–50 Unlike other studies that focused on a single branch, often the Army,21,26,50 this study included active duty personnel from all branches, and TBI exposure varied greatly by branch. In this population-based study, TBI prevalence on the most recent deployment was more than 24% of Army personnel, followed by the Marine Corps (18.9%) and Coast Guard (9.6%), with the lowest TBI prevalence in the Navy (4.8%) and Air Force (4.7%) (data not shown).
We cannot draw causal inferences from a cross-sectional design. As with most studies of combat-acquired TBI, we relied on self-report measures of TBI symptoms rather than a clinical determination of TBI immediately after an injury event. In addition, we did not know lifetime history of TBI from prior deployments, non–combat-related exposures, or multiple injury exposures.28,51 The presence of prior TBIs may interfere with military personnel's ability to process the combat exposure or deployment in general and indirectly influence frequent binge drinking behavior. Furthermore, the survey did not ask precise questions about drinking behavior prior to deployment, so we did not know whether drinking behavior changed for any respondents and, if so, for which groups. Furthermore, by including only 2 groups in our analyses, in which the “other” group included those with less frequent binge drinking, as well as light drinkers and nondrinkers, the risks of less frequent binge drinking were not considered. To some degree, these unknowns would add to measurement error in our models, yet we found a significant relation between TBI and frequent binge drinking despite these possibilities.
Reflecting the HRB Survey question wording on “experiences,” we did not know important details about the nature of blast or other injury events. Effects of a blast, for example, could vary widely on the basis of distance, enclosure, surroundings, postinjury actions, and other injuries in addition to the blast. We did not have any head injury severity measures. The HRB Survey instrument asked military personnel whether they had “experienced” the events (blast/explosion etc) but did not ask explicitly whether they had been “injured” by these events.
As previously noted, the most severe response category was “an LOC of greater than 20 minutes,” which did not allow us to isolate those with a moderate or severe TBI from those with a mild TBI.25 Because of the small sample size, we collapsed those with an LOC of 1 to 20 minutes and those with an LOC of greater than 20 minutes into 1 response category. It is possible that those with moderate or severe TBI could skew the findings for TBI-LOC 1+. However, this is not likely for several reasons. Most military personnel with moderate or severe head injury would be medically evacuated and some would not return to their permanent duty station. Within 1 year, some may still be in medical or rehabilitation facilities, medically separated from the military, or otherwise not eligible to participate in the survey. While the cutoff points for LOC did not follow traditional definitions, a sensitivity analysis conducted post hoc revealed minimal changes in the pattern of findings, and explanatory power showed a slight advantage for the groupings we used.
This is the first study to use a population-based assessment of the active duty component of the armed forces to assess the association of combat-acquired TBI and frequent binge drinking in those returning from a combat deployment in the past year. This study is comprehensive in that it is worldwide, covers all branches of the active duty military, and was administered with the same dual-mode administration method throughout. Unlike previous studies that used convenience samples21,22,26,37 and were restricted to 1 service branch,4,21,26,50 this study has the unique ability to estimate prevalence for the armed forces as a whole. Our population estimates are that among 393 884 active duty military personnel with a past year combat deployment, 87 915 personnel engaged in frequent binge drinking. Furthermore, 137 625 personnel were exposed to at least 1 injury event, and 41 727 reported symptoms consistent with a combat-acquired TBI, the majority with altered consciousness (n = 23 286), and 18 441 military personnel with LOC. The finding that TBI-AC was associated with frequent binge drinking suggests that the armed forces and health care providers should not ignore mild TBI when considering whether returning military personnel are at risk for postdeployment consequences.
This study had other methodological strengths. Although, the HRB Survey is cross sectional in design, we chose respondents with a recent combat deployment. Thus, the outcome of interest, frequent binge drinking in the past 30 days, occurred after the deployment but in close proximity to the injury and TBI event, strengthening our ability to draw conclusions. Limiting our sample to those with a deployment in the past year may also have reduced recall bias relating to injury events and TBI. Also, since the HRB Survey was administered anonymously, respondents had nothing to lose by disclosing sensitive behavioral health information, such as drinking behaviors and comorbidities.52 Similarly, there were no incentives to overreport combat-related injuries or behavioral health conditions, such as TBI or PTSD, as no medical benefits or job performance assessments were linked to the anonymous survey.
We outline implications of this study for clinical practice, public health interventions, and future research directions. Our findings highlight the importance of routine postdeployment screening for both TBI and PTSD and suggest that the presence of either or both of these conditions could trigger targeted alcohol assessment and brief counseling for those with unhealthy drinking behaviors, other brief interventions for those with frequent binge drinking, and referral to treatment for those with alcohol use dependence. Conversely, among those currently experiencing alcohol use problems, these findings suggest careful assessment of underlying TBI and PTSD comorbidities to understand whether and how these might be contributing to alcohol behaviors. Screening and brief interventions, particularly those done in primary care settings, have been effective in identifying those with problem drinking and helping these individuals reduce drinking and change unhealthy drinking patterns.53–58 Furthermore, when deployed military personnel have been exposed to a potentially brain-injuring event such as a blast, the military could provide additional alcohol education and alcohol brief counseling designed to encourage them to rethink their drinking behaviors.33 Current evidence suggests that these interventions may be most effective when offered by trained medical personnel in health care settings.
More research is needed that captures data on TBI-inducing combat events at the time of the injury. Surveys of injury events and TBI symptoms should be worded in ways that are consistent with clinical literature. Specifically, we recommend that future versions of the HRB Survey be strengthened by altering the response categories for severity of TBI to be able to isolate those with a mild TBI from those with moderate or severe injuries. In addition, respondents who report having been exposed to an “injury event” on a deployment could be prompted to report the types of injuries that resulted from the exposure event.
In sum, more research is needed to explore how TBI is related to postdeployment drinking behaviors. This study cannot answer the question whether TBI causes the increased likelihood of frequent binge drinking among active duty military personnel. It is unclear whether the change in the dose-response relation between TBI and drinking that occurred when mental health covariates were accounted for was due to an interaction among the variables or instead was due to sample size, measurement error, or some other artifact. More studies are warranted to explore these relations.
This study suggests that experiencing a combat-acquired TBI, even mild TBI with altered consciousness only, is associated with frequent binge drinking after deployment. In addition to being contraindicated for TBI patients, this level of unhealthy drinking interferes with postdeployment reintegration and complicates healing from other combat-related injuries and conditions such as PTSD. The DOD may improve the health and well-being of military personnel by mounting evidence-based screening and brief interventions for unhealthy drinking in primary care and other medical settings for postdeployment military personnel with self-report of possible TBI events.
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*We define TBI based on self-report elicited by the HRB Survey method. It does not represent a clinical diagnosis or an observed event.
Keywords:© 2012 Lippincott Williams & Wilkins, Inc.
binge drinking; combat; deployment; military personnel; posttraumatic stress disorder; traumatic brain injury