Neuropsychological studies of mild traumatic brain injury: a meta-analytic review of research since 1995.

A meta-analysis conducted by Binder, Rohling and Larrabee established a relationship between mild traumatic brain injury (TBI) and small reductions in cognitive functioning in individuals assessed more than 3 months post-injury. As a follow-up, this study summarized similar research that (1) was published since the previous meta-analysis, and (2) included data collected at any stage post-injury. An extensive literature search revealed 17 suitable studies from which effect sizes were aggregated. The overall effect size was g = 0.32, p < .001. Speed of processing measures had the largest effect, g = 0.47, p < .001. The merging of post-acute effect sizes with those reported in Binder et al.'s review yielded a nonsignificant result, g = 0.11. Time since injury was found to be a significant moderator variable, with effect sizes tending to zero with increasing time post injury.