WISC-III freedom from distractibility as a measure of attention in children with and without Attention Deficit Hyperactivity Disorder

WISC-III data were analyzed in clinical samples of 87 children with ADHD and 32 children without ADHD. Mean FSIQ (Full Scale IQ) exceeded FDI (Freedom from Distractibility Index) at all ages from 6 to 16 years in the ADHD group but not in the nonADHD group. Further, the discrepancy between FSIQ and FDI was significantly greater in the ADHD group. The four lowest mean subtest scores for the ADHD group were Digit Span, Arithmetic, Coding, and Symbol Search, which was not the case for the nonADHD group. For significantly more children with ADHD (87%), the score for FDI plus the Processing Speed Index was less than the sum of the two remaining Index scores (VCI+POI). No children without ADHD had Digit Span and Arithmetic as two of their three lowest subtest scores, whereas this was found for 23% of children with ADHD. The presence of mood, behavior, or learning disorders affected scores in some cases. An independent replication study involving 52 referred children with ADHD and 23 without ADHD supported these findings.