Interactive effects of cumulative lifetime traumatic brain injuries and combat exposure on posttraumatic stress among deployed military personnel.

Growing research links Traumatic Brain Injury (TBI) with greater posttraumatic stress disorder (PTSD) symptoms. Much of this research has focused on the influence of the presence or severity of a single TBI while neglecting the potential cumulative effects of multiple TBIs incurred across an individual's lifetime on combat-related PTSD. The present study addressed this gap using a sample of 157 military service members and 4 civilian contractors who underwent structured TBI interviews at a military hospital in Iraq and completed the Combat Experiences Scale (CES) and Posttraumatic Checklist - Military (PCL-M). Results indicated that a greater number of lifetime TBIs were associated with greater PTSD symptoms when accounting for the presence and severity of a recent, deployment-related TBI. Additionally, a significant interaction of number of lifetime TBIs and combat exposure emerged, indicating that exposure to combat yielded greater PTSD symptoms among those with multiple lifetime TBIs compared to those with one or zero lifetime TBIs. These data suggest that incurring multiple TBIs may amplify the link between combat exposure and PTSD and underscore the need to screen for lifetime TBI history.