Relationship Between Processing Speed and Executive Functioning Performance Among OEF/OIF Veterans: Implications for Postdeployment Rehabilitation

Background: Comorbid mild traumatic brain injury (mTBI) with posttraumatic stress disorder (PTSD) is a common clinical presentation among troops returning from Operation Enduring Freedom and Operation Iraqi Freedom (OEF/OIF). This study examined processing speed and executive functioning in a sample of OEF/OIF veterans who had sustained mTBI, a subset of whom also had comorbid PTSD. Methods: Fifty-three OEF/OIF veterans with a history of mTBI completed Wechsler Adult Intelligence Scale-III Symbol Search and Digit Symbol-Coding subscales, Stroop Word, color and color-word trials, and Trail Making Test, Parts A and B as part of a comprehensive neuropsychological test battery. Results: Excluding from analysis those who scored poorly on effort testing, multiple regression showed that measures of processing speed accounted for 43% of the variance in performance on the Trail Making Test, Part B and 50% of the variance in performance on the Stroop task. Significant differences in processing speed and executive functioning were found on the basis of presence of comorbid PTSD. Stroop Color (F = 9.27, df = 52, P < .004) and Stroop Color Word (F = 7.19, df = 52, P < .01) scores differed significantly between the groups. Those having comorbid PTSD (+TBI/+PTSD) scored significantly poorer than the mTBI-only group (+TBI/-PTSD). Implications for treatment of the comorbid conditions are discussed.