The Differential Impact of Alcohol and Interpersonal Violence on the Severity of Violent Traumatic Brain Injuries among American Indians.

Research shows connections between substance use and traumatic brain injury (TBI), high rates of substance use and interpersonal violence (IPV) in American Indians with TBI, and connections between IPV and TBI. This study assessed the effects of substance use at the time of a violent TBI and possible mediators such as American Indian race on injury severity (injury severity score [ISS]). A secondary data analysis of 3,351 individuals who experienced a TBI due to violence was conducted. American Indians with TBI were more likely to experience IPV (χ2 = 4.19; p = .04) and had significantly higher blood alcohol content level (BAC) scores (t = - 16.78; p = .000) than other racial groups. A regression model explained 27% of the variance in ISS. Significant interaction terms uncovered positive relationships between: (a) American Indian race and ISS when the injury aetiology was not IPV and BAC scores were lower than the legal limit, and (b) IPV and ISS when patients were not American Indian. Alcohol was negatively associated with ISS among American Indians, suggesting that BAC may impact individuals with TBI differentially as a function of race.