Executive Functioning and Anterior Cingulate Cortex Volume as Potential Moderators of the Combat Exposure-PTSD Relationship

Combat, a common source of trauma in the military, is consistently predictive of post-traumatic stress disorder (PTSD) among service members deployed to Iraq and Afghanistan. PTSD has detrimental effects on post-deployment health and psychosocial functioning. The cognitive model of PTSD posits that automatic threat appraisals maintain PTSD when they generalize to safe situations. As a result, the ability to modify this automatic response may support re-adaptation to the civilian context following deployment. Executive functioning (EF) includes suppressing automatic, incorrect responses (inhibition), generating and holding on to alternative, more context-appropriate perspectives (working memory), and flexibly shifting toward them (cognitive flexibility) and may act as a buffer by enabling re-consideration of trauma appraisals that otherwise maintain the combat exposure-PTSD relationship. Additionally, the anterior cingulate cortex (ACC), a brain region within the ventromedial prefrontal cortex, supports decision-making in uncertain contexts, regulating emotion to prevent incorrect automatic threat responses. Consequently, a smaller ACC volume may be associated with a diminished ability to adjust incorrect automatic threat appraisals. Using data from the Chronic Effects of Neurotrauma Consortium Study 34 (CENC-34) examining health outcomes following combat exposure and neurotrauma, the present study examined the factor structure of EF, and examined the resulting EF components and ACC volume as moderators in the relationship between combat exposure and PTSD, including PTSD symptom severity as well as diagnostic status. Participants were Iraq and Afghanistan Veterans (N = 241) who passed performance and symptom validity thresholds. Factor analysis of EF tests yielded two components, Cognitive Flexibility and Working Memory. After adjusting for age, sex, years of education, time since trauma, current Major Depressive Disorder (MDD) diagnosis, and presence of deployment mTBI, EF components were not associated with PTSD symptoms or diagnosis, and no support was found for an interaction between either component and combat exposure. In these models, combat exposure was significantly associated with PTSD symptoms and PTSD diagnosis. Similarly, after adjusting for age, current MDD diagnosis, presence of deployment mTBI, and total intracranial volume, combat exposure and ACC volume were not associated with PTSD symptoms or diagnosis and results did not support an interaction effect between combat exposure and ACC volume. Unexpectedly, across all models, current MDD diagnosis was the most consistently predictive of PTSD symptoms and PTSD diagnostic status. The present work was an initial foray toward advancing theoretical, empirical, and clinical understandings of the factors contributing to persistent PTSD in Veterans. Our replication of the association between MDD and PTSD underscores the need to comprehensively assess for relevant comorbidities in clinical settings. Additionally, with combat exposure as a significant predictor of PTSD symptom severity, individuals exposed to combat may benefit from periodic screenings to enable early detection and intervention.