Role of Pre-Morbid Factors and Exposure to Blast Mild Traumatic Brain Injury on Post-Traumatic Stress in United States Military Personnel.

Mild traumatic brain injury (mTBI), the signature injury of the recent wars in Afghanistan and Iraq, is a prevalent and potentially debilitating condition that is associated with symptoms of post-traumatic stress/post-traumatic stress disorder (PTS/PTSD). Prior mTBI, severity and type of injury (blast vs. non-blast), and baseline psychiatric illness are thought to impact mTBI outcomes. It is unclear if the severity of pre-morbid PTS/PTSD is a risk factor of post-injury levels of PTS and mTBI symptoms. The objective of the study was to examine predictors of post-injury PTS/PTSD, including pre-morbid PTS symptoms, and physical and cognitive symptoms in the sub-acute phase (1 week-3 months) following an acute mTBI. A retrospective review of medical records was performed of 276 servicemen assigned to the United States Army Special Operations Command referred for mTBI evaluation between December 2009 and March 2011. Post-Concussion Symptom Scale and PTSD Checklist scores were captured pre- and post-injury. A total of 276 records were reviewed. Pre-morbid and post-injury data were available for 91% (251/276). Of the 54% (136/251) of personnel with mTBI, 29% (39/136) had positive radiology findings and 11% (15/136) met criteria for clinical PTS symptoms at baseline. Logistic regression analysis found baseline PTS symptoms predicted personnel who met clinical levels of PTSD. Receiver operating characteristic curve analysis revealed that baseline PTS (p = 0.001), baseline mTBI symptoms (p = 0.001), and positive radiology (magnetic resonance imaging or computed tomography) findings for complicated mTBI (p = 0.02) accurately identified personnel with clinical levels of PTSD following mTBI. Years of military service, combat deployment status, age, and injury mechanism (blast vs. non-blast) were not associated with increased risk of PTS following mTBI. Pre-morbid PTS symptoms are associated with an increased risk for clinical levels of PTS following a subsequent mTBI. Symptom severity and positive radiologic findings may amplify this risk. At-risk personnel may benefit from early identification and intervention.