A REVIEW OF MILD HEAD TRAUMA .1. METAANALYTIC REVIEW OF NEUROPSYCHOLOGICAL STUDIES

We conducted a meta-analytic review of neuropsychological studies of m ild head trauma (MHT). Studies were included if they met these criteri a: patients studied at least 3 months after MHT; patients selected bec ause of a history of MHT rather than because they were symptomatic; an d attrition rate of less than 50% for longitudinal studies. Studies of children were not considered. We found a total of 8 published papers with 11 samples that met these criteria. Using the g statistic, the ov erall effect size of 0.07 was nonsignificant, but the d statistic yiel ded an effect size of 0.12, p < .03. Measures of attention had the lar gest effect, g = 0.17. p < .02 and d = 0.20, p < .096. Severity of inj ury accounted for far more variance than did specific neuropsychologic al domain, however. The small effect size suggests that the maximum pr evalence of persistent neuropsychological deficit is likely to be smal l and neuropsychological assessment is likely to have positive predict ive value of less than 50%. Consequently, clinicians will more likely be correct when not diagnosing brain injury than when diagnosing a bra in injury in cases with chronic disability after MHT.