Neurobehavioral Symptoms Partially Mediate the Effects of Depression and PTSD on Participation for Veterans With Mild Traumatic Brain Injury: A Cross-Sectional Study

Objective: To examine whether neurobehavioral symptoms mediate the relationship between comorbid mental health conditions (major depressive disorder [MDD] and/or posttraumatic stress disorder [PTSD]) and participation restriction among Veterans with mild traumatic brain injury (mTBI). Setting: Veterans Health Administration (VHA). Participants: National sample of Veterans with mTBI who received VHA outpatient care between 2012 and 2020. Design: Secondary data analysis of VHA clinical data. We specified a latent variable path model to estimate relationships between: (1) comorbid mental health conditions and 3 latent indicators of neurobehavioral symptoms (vestibular-sensory; mood-behavioral; cognitive); (2) latent indicators of neurobehavioral symptoms and 2 latent indicators of participation restriction (social and community participation; productivity); and (3) comorbid mental health conditions and participation restriction. Main Measures: International Classification of Diseases codes, Neurobehavioral Symptom Inventory, and Mayo-Portland Adaptability Inventory Participation Index to measure mental health conditions, neurobehavioral symptoms, and participation restrictions, respectively. Results: Indirect effect estimates indicated that comorbid MDD and/or PTSD was associated with greater social and community participation restrictions, as mediated by mood-behavioral ( β = .22-.33; 99% CI 0.18-0.4; small to medium effect) and cognitive symptoms ( β = .08-.13; 99% CI 0.05-0.18; small effect), and with greater productivity restrictions, as mediated by vestibular-sensory ( β = .06-.11; 99% CI 0.04-0.15; small effect) and cognitive symptoms ( β = .08-.13; 99% CI 0.05-0.18; small effect). Direct effect estimates indicated that comorbid MDD and/or PTSD was associated with greater challenges with both social and community participation ( β = .19-.40; 99% CI 0.12-0.49; small to medium effect) and productivity ( β = .08-.44; 99% CI −0.02 to 0.55; small to medium effect). Conclusion: Neurobehavioral symptoms partially mediated the impact of MDD and/or PTSD on participation restrictions among Veterans with mTBI. These findings advance the understanding of explanatory mechanisms underlying participation challenges among Veterans with comorbid mTBI and mental health challenges, thereby informing the development of tailored intervention strategies.