Study of the Cognitive Functioning of Medicated and Non-Medicated Elementary School-Aged Children Diagnosed with Attention Deficit HyperactivIty Disorder

Attention Deficit Hyperactivity Disorder (ADHD) is a serious disability that has been shown to adversely affect cognition, affect, and behavior. Research using traditional measures of cognitive functioning, such as intelligence tests has shown that children diagnosed with ADHD perform poorly on cognitive measures of processing speed, and on working memory in particular (Kerns, Mclnerney & Wilde, 2001; Weiler, Bernstein, Bellinger & Waber, 2000). Mahone, et al. (2003), note that reviews involving the Wechsler Scales for children suggest that Full Scale IQ scores (FSIQ) on the WISC-III average 5 to 6 points lower than scores in the WISC-R. It was hypothesized that changes on revised subtests of the WISC-III Performance Scale may place ADHD children at a disadvantage if their performance on these subtests is compared to their performance on analogous WISC-R subtests. Mahone, et al. (2003) theorize that increased executive demands resulted in lower FSIQ scores and call for further analysis upon future Wechsler revisions. Although results are equivocal, research suggests that psychostimulant medication may ameliorate ADHD cognitive deficiencies that adversely impact working memory and processing speed. Brown and Borden (1989) suggest that stimulant drug improvement occurs primarily on rote or simple tasks, but measures emphasizing the processing of higher-order information may be less influenced. Barkley (1998) indicates that the impact of drugs upon behavior and concentration was most salient, with performance on intelligence tests unaffected by medication. However, most of these studies extrapolated IQ scores either from short forms or from several subtests of the Wechsler scales. Research using more traditional measures of cognitive functioning (e.g., standardized intelligence tests), and focusing on long-term effects of cognitive performance (Gillberg, et aI., 1997; Livingston, Mears, Marshall, Gray & Haak, 1996; Mahone, et aI., 2003), suggests that results depend on the measures and methods used. As part of the initial validation of the revised WISC-IV, an ADHD group was compared to a matched control group. Additional research called for investigations comparing the performance of medicated ADHD children with nonmedicated ADHD children. This research used the Wechsler Intelligence Test for Children-fourth edition (WISC-IV) to assess the cognitive performance of medicated ADHD children and nonmedicated ADHD children. Results were used to answer the questions: Are there differences in IQ scores between ADHD children and normal controls, and between medicated ADHD children and nonmedicated ADHD children