Depression and neuropsychological functioning in mild traumatic brain injury

The present study examined the relationship between depression (as measured by the Dysthymia scale of the Millon Clinical Multiaxial Inventory-II MCMI-II and the Depression, DEP, and Harris-Lingoes Depression scales of the Minnesota Multiphasic Personality Inventory-2 MMPI-2), and neuropsychological functioning (as measured by the Category Test, Logical Memory, Visual Reproduction, Trail Making Test B, and Consonant Trigrams) in individuals who have experienced a mild traumatic brain injury (MTBI). Additionally, the influence of gender upon the depression/cognition relationship was examined. These issues were examined in two independent patient samples using the clinical files from two private clinical neuropsychology practices with one group (n = 72) having completed the MCMI-II and the other group (n = 50) having completed the MMPI-2.

A series of hierarchical regression analyses indicated that depression, as measured by scales of both the MCMI-II and MMPI-2, was largely independent of cognitive performance with the exception of a modest inverse relationship ($p<.05$) noted between Logical Memory and depression, as measured by the MCMI-II. Depression was common in both samples for males as well as females and the depression/cognition relationship did not differ according to gender. Reports of pain in both samples were even more common than depression and supplementary analyses revealed an inverse relationship between pain and cognitive performance on verbal and visual memory tasks.

Future research should incorporate prospective research designs using larger samples whereby consecutive series of MTBI patients (e.g., presenting at a hospital emergency department) are followed from time of injury and then at selected postinjury dates. Patients enrolled could then eventually be divided into those with and those without ongoing complaints in order to determine whether neuropsychological deficits seen in patients with chronic symptomatology are also seen in MTBI patients who do not report postconcussive difficulties and require ongoing care. It would also be beneficial to compare the two groups in terms of psychological factors (e.g., depression, anxiety, hypochondriasis, etc.) as well as pain level in relation to cognitive functioning. Enhanced knowledge of factors that contribute to persistent post-MTBI symptoms should assist in the development of preventative strategies which could be directed at 'high risk' candidates for chronic sequelae.