Psychological disturbance, incomplete effort, and compensation-seeking status as predictors of neuropsychological test performance in head injury.

Indices from the Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989) representing cognitive and emotional disturbance as well as incomplete effort on the Recognition Memory Test (RMT; Warrington, 1984) were examined as predictors of performance on the Halstead-Reitan Neuropsychological Test Battery (HRB; Reitan & Wolfson, 1993). In the current study, which included a large sample (N = 369) of patients referred for neuropsychological (NP) evaluation after presumptive head injury, MMPI-2 measures of psychological disturbance accounted for as much as 25% of the variance in HRB test scores, resulting in a moderate overall effect size (median Adj. R(2) = .16; R = .40). When demographic variables, head injury severity, and compensation-seeking status were entered in previous steps, incomplete effort as defined by chance performance on the RMT accounted for between 2% and 13% of the variance in HRB test scores, with modest overall effect size (median R(2) Delta = .07; R = .26) in multiple regression equations. Additionally, when MMPI-2 indices of psychological disturbance were included in the last step, they accounted for 2% to 11% of additional variance, retaining a modest overall effect (median R(2) Delta = .03; R = .17). Compensation-seeking status and injury severity as measured by duration of post-traumatic amnesia were, at best, modestly related to NP test performance. Findings confirm the reliable relationship between test performance and psychological disturbance as well as incomplete effort when assessing dysfunction following head injury. In contrast to previous studies, incomplete effort was unrelated to compensation-seeking status.