Longitudinal Effects of Mild Traumatic Brain Injury and Posttraumatic Stress Disorder Comorbidity on Postdeployment Outcomes in National Guard Soldiers Deployed to Iraq

Context: Troops deployed to Iraq and Afghanistan are at high risk for exposure to combat events resulting in mild traumatic brain injury (MTBI) or concussion and posttraumatic stress disorder (PTSD). The longer-term impact of combat-related concussion/MTBI and comorbid PTSD on troops' health and well-being is unknown. Objective: To assess longitudinal associations between concussion/MTBI and PTSD symptoms reported in theater and longer-term psychosocial outcomes in combat-deployed National Guard soldiers. Design: Longitudinal cohort study. Participants were surveyed in Iraq 1 month before returning home (time 1) and 1 year later (time 2). Self-reports of concussion/MTBI and PTSD were assessed at times 1 and 2. Based on time 1 concussion/MTBI status (defined as an injury during deployment with loss of consciousness or altered mental status) and time 2 postdeployment probable PTSD status, soldiers were compared on a range of time 2 psychosocial outcomes. Participants: Nine hundred fifty-three US National Guard soldiers. Setting: The time 1 sample was assessed during redeployment transition briefings held at military installations in the Iraq combat theater. The time 2 sample was assessed using mailed surveys sent to the homes of US National Guard service members. Main Outcome Measures: Postconcussive, depression, and physical symptoms; alcohol use; social functioning; and quality of life assessed at time 2 using valid clinical instruments. Results: The rate of self-reported concussion/MTBI during deployment was 9.2% at time 1 and 22.0% at time 2. Soldiers with a history of concussion/MTBI were more likely than those without to report postdeployment postconcussive symptoms and poorer psychosocial outcomes. However, after adjusting for PTSD symptoms, concussion/MTBI was not associated with postdeployment symptoms or outcomes. Time 1 PTSD symptoms more strongly predicted postdeployment symptoms and outcomes than did concussion/MTBI history. Conclusions: Although combat-related PTSD was strongly associated with postconcussive symptoms and psychosocial outcomes 1 year after soldiers returned from Iraq, there was little evidence of a long-term negative impact of concussion/MTBI history on these outcomes after accounting for PTSD. These findings and the 2-fold increase in reports of deployment-related concussion/MTBI history have important implications for screening and treatment.