The relation between posttraumatic stress disorder and mild traumatic brain injury acquired during Operations Enduring Freedom and Iraqi Freedom.

OBJECTIVE

To understand the relations of mild traumatic brain injury (TBI), blast exposure, and brain white matter structure to severity of posttraumatic stress disorder (PTSD).

DESIGN

Nested cohort study using multivariate analyses.

PARTICIPANTS

Fifty-two OEF/OIF veterans who served in combat areas between 2001 and 2008 were studied approximately 4 years after the last tour of duty.

MAIN MEASURES

PTSD Checklist-Military; Combat Experiences Survey, interview questions concerning blast exposure and TBI symptoms; anatomical magnetic resonance imaging (MRI), and diffusion tensor imaging (DTI) scanning of the brain.

RESULTS

PTSD severity was associated with higher 1st percentile values of mean diffusivity on DTI (regression coefficient [r] = 4.2, P = .039), abnormal MRI (r = 13.3, P = .046), and the severity of exposure to combat events (r = 5.4, P = .007). Mild TBI was not significantly associated with PTSD severity. Blast exposure was associated with lower 1st percentile values of fractional anisotropy on DTI (odds ratio [OR] = 0.38 per SD; 95% confidence interval [CI], 0.15-0.92), normal MRI (OR = 0.00, 95% likelihood ratio test CI, 0.00-0.09), and the severity of exposure to traumatic events (OR = 3.64 per SD; 95% CI, 1.40-9.43).

CONCLUSIONS

PTSD severity is related to both the severity of combat stress and underlying structural brain changes on MRI and DTI but not to a clinical diagnosis of mild TBI. The observed relation between blast exposure and abnormal DTI suggests that subclinical TBI may play a role in the genesis of PTSD in a combat environment.