A path analysis of combat-acquired traumatic brain injury and posttraumatic stress disorder and their relative associations with post-deployment binge drinking

Studies suggest that drinking after a traumatic brain injury (TBI) may be problematic. Research on unhealthy alcohol consumption after combat-acquired TBI is in its infancy despite high rates of both binge drinking and TBI among active duty military personnel (ADMP). The purpose of this paper is to determine if combat-acquired TBI is an independent risk factor for two alcohol related outcomes: 1) frequent binge drinking - 5 or more drinks on the same occasion, at least once per week, in the past 30 days (4 or more for women), and 2) negative drinking-related consequences measured by 22 social, medical, and military-specific negative consequences (0-22), or whether its effect is almost entirely through posttraumatic stress disorder (PTSD). TBI is measured by a hierarchal variable that captures the severity of TBI, and a positive screen for PTSD is based on the standard diagnostic cutoff score of 50+ on the PCL-C. We report findings from several multivariate models that adjust for demographics, lifetime combat exposure, and a positive screen of PTSD. This study analyzes the 2008 Department of Defense Survey of Health Related Behaviors, an anonymous, worldwide survey completed by 28,546 ADMP (70.6% response rate). The selected study sample is ADMP who returned from a combat deployment in the past 12 months (N = 7,155). Data are weighted to account for the complex sampling design. 25.6% are frequent binge drinkers and 13.9% experienced a self-reported TBI during their last deployment. In logistic regression models, ADMP with TBI had 1.67 the odds of frequent binge drinking in the past month compared to those without TBI (95% CI, 1.00-2.79). Negative binomial regressions found that ADMP who experienced a TBI with a loss of consciousness of more than 20 minutes were estimated to have 4.10 times (95% CI, 1.72-9.65) the number of drinking-related consequences as those without a TBI. This estimate remained consistent when controlling for frequent binge drinking, suggesting that the higher rate of consequences among those with TBI was not even partially explained by increased frequent binge drinking among this group. Path analysis techniques determined that both direct and indirect effects (through PTSD) of TBI on past-month binge drinking were significant. Implications for preventive interventions, future research, and policy will be discussed.