Increased risk of alcohol dependency in a cohort of National Guard troops with PTSD: a longitudinal study.

Studies show high rates of co-morbid post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD) but there is no consensus on the causal direction of the relationship. Some theories suggest AUD develops as a coping mechanism to manage PTSD symptoms and others that AUD is a vulnerability factor for PTSD. A third hypothesis posits independent developmental pathways stemming from a shared etiology, such as the trauma exposure itself. We examined these hypotheses using longitudinal data on 922 National Guard soldiers, representing a subsample (56%) of a larger pre- and post-deployment cross-sectional study of New Jersey National Guard soldiers deployed to Iraq. Measures included the PTSD Checklist (PCL), DSM-IV-based measures of alcohol use/misuse from the National Household Survey of Drug Use and Health and other concurrent mental health, military and demographic measures. Results showed no effect of pre-deployment alcohol status on subsequent positive screens for new onset PTSD. However, in multivariate models, baseline PTSD symptoms significantly increased the risk of screening positive for new onset alcohol dependence (AD), which rose 5% with each unit increase in PCL score (AOR = 1.05; 95% CI = 1.02-1.07). Results also supported the shared etiology hypothesis, with the risk of a positive screen for AD increasing by 9% for every unit increase in combat exposure after controlling for baseline PTSD status (AOR = 1.09; 95% CI = 1.03-1.15) and, in a subsample with PCL scores <34, by 17% for each unit increase in exposure (AOR = 1.17; 95% CI = 1.05-1.31). These findings have implications for prevention, treatment and compensation policies governing co-morbidity in military veterans.