An Investigation of Relationships between PTSD Symptoms, Blast Exposure, and Neuropsychological Outcomes among U.S. Veterans

Previous studies of U.S. military veterans have consistently demonstrated a significant effect of increased PTSD on decreased neuropsychological functioning. While studies have not consistently demonstrated a relationship between combat-related blast exposure (BE) and neuropsychological outcomes, alterations in neuronal function of white matter pathways associated with cognitive function have been associated with greater BE severity. The aim of this study was to evaluate the effect of PTSD symptoms on neuropsychological functioning in a cohort of US military veterans from recent military conflicts (N=480), and to also examine the effects of PTSD symptom clusters (i.e., reexperiencing, avoidance, numbing, and hyperarousal symptoms) on neuropsychological functioning. An additional aim was to assess for a potential additive moderation effect of BE severity on the relationship between PTSD symptoms and neuropsychological functioning. These interrelationships were evaluated in a sample of 348 U.S. veterans (Mage=31.8 years, Meducation=14.0 years) via path analysis. Inclusion of BE severity as a moderator did not significantly increase the effect of PTSD on neuropsychological function, and effect sizes were small for each of the four neuropsychological domains after accounting for confounders (Attentional Processing Speed: R2=.066; Executive Function: R2=.038; Fine Motor Function: R2=.064; Verbal Memory: R2=.055). When examining the moderation effect of BE severity on PTSD symptom clusters, a small but significant moderation effect was found on the relationship between Avoidance symptoms and Executive Function (β=-.183 [95% CI=-.356, -.010], SE=.088, p<.05). BE severity did not have an additive effect for any other relationships between PTSD symptom clusters and neuropsychological performances. This study replicated the greater effect that PTSD symptoms have on neuropsychological functioning in comparison to combat-related BE. Differences in relationships between individual PTSD symptom clusters and neuropsychological outcomes supported ongoing investigation of symptom clusters rather than just total PTSD symptoms. Future studies of these conditions will benefit from use of structural equation modeling techniques in order to evaluate the effects of latent variables on these interrelationships.