Identifying Unique Symptom Groups Following Mild Traumatic Brain Injury Using the Neurobehavioral Symptom Inventory and PTSD Checklist-5 in Military Personnel: A Bifactor Analysis

Objective:To identify both shared and unique groups of posttraumatic stress and postconcussive symptoms using bifactor analysis.Setting:Two large military outpatient traumatic brain injury (TBI) rehabilitation clinics in the Southwestern United States.Participants:A sample of 1476 Active Duty Service Members seeking treatment for a mild TBI sustained more than 30 days previously, without history of moderate or severe TBI, who completed measures of postconcussive and posttraumatic stress symptoms assessed at clinic intake.Design:Observational, correlational study with data taken from an institutional review board-approved clinical registry study.Main Measures:Neurobehavioral Symptom Inventory (NSI) and Posttraumatic Stress Disorder (PTSD) Checklist for Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) (DSM-V) (PCL-5). Concurrent measures were Patient Health Questionnaire (PHQ-8), Pittsburgh Sleep Quality Index (PSQI), and Headache Impact Test (HIT-6).Results:Results identified a bifactor model demonstrating unique posttraumatic stress, depressive, cognitive, and neurological/somatic symptom groups that were still evident after accounting for a universal factor representing general distress. These symptom groups were differentially related to concurrently measured clinical outcomes.Conclusion:Use of a bifactor structure may help derive clinically useful signals from self-reported symptoms among Active Duty Service Members seeking outpatient treatment for mild TBI.