Wechsler Adult Intelligence Scale-Third Edition findings in relation to severity of brain injury in litigants

WAIS-III findings were reported for 150 litigants, classified into three groups according to severity of traumatic brain injury (TBI), and a general population control group. There was a significant "dose response" relationship between TBI severity and all Index/IQ scores. Effect size was greatest for the Processing Speed Index (PSI). Between group differences were significant on all subtests except Information and Digit Span. Effect sizes were greatest for Digit Symbol, Symbol Search, Similarities, and Picture Arrangement. Relative to the control group, there was a significant difference for the Severe and Extremely Severe TBI groups on all IQ/Index scores and most subtests. The Moderate TBI group differed significantly on one Index (the PSI) and none of the subtests. Clinical implications of the findings are discussed in relation to the utility of the WAIS-III in assessing the cognitive sequelae of TBI, the use of current WAIS-III IQ scores to assess intelligence-memory discrepancies, WAIS-III short forms, and estimation of premorbid intelligence.