Longitudinal study of objective and subjective cognitive performance and psychological distress in OEF/OIF Veterans with and without traumatic brain injury.

OBJECTIVE: To describe changes in post-deployment objective and subjective cognitive performance in combat Veterans over 18 months, relative to traumatic brain injury (TBI) status and psychological distress.

METHOD: This prospective cohort study examined 500 Veterans from Upstate New York at four time points, six months apart. TBI status was determined by a structured clinical interview. Neuropsychological instruments focused on attention, memory, and executive functions. Subjective cognitive complaints were assessed with the Neurobehavioral Symptom Inventory (NSI). A psychological distress composite included measures of post-traumatic stress disorder (PTSD), depression, and generalized anxiety.

RESULTS: Forty-four percent of the sample was found to have sustained military-related TBI, 97% of which were classified as mild (mTBI), with a mean time since injury of 41 months. Veterans with TBI endorsed moderate cognitive symptoms on the NSI. In contrast to these subjective complaints, mean cognitive test performance was within normal limits at each time point in all domains, regardless of TBI status. Multilevel models examined effects of TBI status, time, and psychological distress. Psychological distress was a strong predictor of all cognitive domains, especially the subjective domain. Substantial proportions of both TBI+ and TBI- groups remained in the clinically significant range at the initial and final assessment for all three distress measures, but the TBI+ group had higher proportions of clinically significant cases.

CONCLUSIONS: Objective cognitive performance was generally within normal limits for Veterans with mTBI across all assessments. Psychological distress was elevated and significantly related to both objective and subjective cognitive performance.