Date of Submission

2009

Degree Type

Dissertation

Degree Name

Doctor of Psychology (PsyD)

Department

Psychology

Department Chair

Robert A. DiTomasso, Ph.D., ABPP

First Advisor

George McCloskey, Ph.D., Chairperson

Second Advisor

Janet Friedman, Ed.D., NCSP

Third Advisor

Daniel H. Ingram, Psy.D.

Abstract

Attention Deficit Hyperactivity Disorder is among the most commonly diagnosed childhood disorders, with symptoms that can cause significant difficulties in the educational setting. Deficits related to working memory and processing speed are thought to be a core feature of ADHD. As such, research using traditional measures of cognitive functioning has shown that children diagnosed with ADHD tend to perform poorly on measures of processing speed and working memory, relative to non-ADHD individuals and relative to measures of other cognitive abilities. Psychostimulant medication is a common treatment for ADHD and research overwhelmingly supports its positive impact on behavior and concentration; however, research related to its impact on cognitive functioning is sparse and findings have been equivocal. The major purpose of the current study was to determine whether or not there are significant differences in the cognitive profiles of individuals with ADHD relative to non-ADHD controls. Of particular interest was the functioning of children with ADHD on measures of processing speed and working memory relative to non-ADHD children and relative to measures of other cognitive abilities. Furthermore, this study was designed to investigate the effects of medication on the performance of ADHD subjects on measures of cognitive functioning. The results of this study found that students with ADHD did perform significantly lower on measures of processing speed and working memory on the WISC-IV relative to non-ADHD subjects and relative to measures of verbal and nonverbal reasoning skills. This lends support to previous research and hypotheses, indicating that working memory and processing speed deficits are a core feature of ADHD. This study did not find significant differences between students who were medicated relative to those who were not on overall IQ, Index, or Subtest scores of the WISC-IV. On the other hand, nonmedicated ADHD subjects were more likely than medicated ADHD subjects to display GAI scores greater than WMI, which provides some support for the positive effects of medication on working memory, although much more research is needed to make this claim. No support for positive medication effects on processing speed was found in this study.

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