Neuropsychological effects of combat-related PTSD in service members deployed to Iraq

Numerous studies have explored the effects of combat-related PTSD on neuropsychological performance. However, no definitive conclusions can be drawn as results vary considerably due to a wide variety of methodological inconsistencies and limitations. The present study investigated the effects of combat-related PTSD on IQ and performance on measures of attention, memory, executive function, visuospatial skills, and gross motor ability in combat-exposed Service Members recently returned from Iraq and diagnosed with PTSD, combat-exposed Service Members without PTSD (CC), and Service Members who have not been deployed (NC). The present study addressed limitations in previous studies, such as controlling for the effect of combat exposure by including a Combat Control group in addition to a Non-Combat Control group. Because previous studies have found lower verbal IQ and neuropsychological impairments in veterans with combat-related PTSD, the present study predicted that (1) the PTSD group would have a lower Verbal IQ, but comparable Full-Scale and Performance IQ as compared to the NC group and (2) the PTSD group would demonstrate poorer performance on neuropsychological tests. The present study also explored (1) the degree to which combat exposure and PTSD severity contributed to performance on neuropsychological measures and (2) how well neuropsychological measures predicted PTSD vs. CC group membership. Although, the present study was limited by small sample size, pairwise comparisons revealed significant effects of PTSD on measures of processing speed and nonverbal abstract reasoning. Regression analyses were consistent with the aforementioned results and also revealed a significant contribution of PTSD severity to Verbal IQ, FSIQ, word knowledge; verbal abstract reasoning, response inhibition, visuoconstructual ability, and visual memory, whereas there was no significant contribution of combat exposure. Furthermore, the combined scores of the Stroop Color and Color-Word trials and Matrix Reasoning subtest correctly classified more than 78% of the combat-exposed sample into PTSD or Non-PTSD using discriminant function analysis. In conclusion, the results demonstrate a significant relationship between PTSD severity and cognitive functioning, and contribute to the existing literature in this field. Limitations to the study and implications for future research are discussed.