Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)




Attention-Deficit/Hyperactivity Disorder (ADHD) is hypothesized to be a disorder of executive functioning; however, results of studies comparing ADHD with control children using executive functioning measures are inconsistent, with some studies showing group differences while others do not. One limitation of these studies has been the failure to control for frequently occurring comorbid psychiatric conditions, such as Oppositional Defiant Disorder (ODD) and Conduct Disorder (CD), in the ADHD groups. Previous studies have demonstrated that children with ADHD and comorbid CD or severe ODD perform significantly better on tests of cognitive/executive functioning when compared to children with ADHD only. Based on these studies, this study tested the hypothesis that children with a single diagnosis of ADHD (ADHD-only) would show deficits on executive functioning measures relative to controls, but that children with a comorbid diagnosis of ADHD and CD or severe ODD (ADHD+SOD/CD) would not show such deficits relative to controls. Also, because ODD and CD are presumed to be caused by negative family environment factors, the family environments of the children in the current study were also examined, and it was hypothesized that children with ADHD+SOD/CD would come from more negative environments than would children with ADHD-only or controls. Evidence of more negative family environments coupled with a lack of neuropsychological deficits was presumed to provide evidence that the ADHD symptoms in children with ADHD+SOD/CD may have environmental rather than neurobiological causes. A total of 56 male and female children participated in this study. One-way ANOVAs were used to compare groups on the executive functioning and family environment measures. Results indicated that children with ADHD-only did more poorly on executive functioning measures when compared with controls; however, children with ADHD+SOD/CD were not found to be significantly different from controls on these measures. In addition, the family environments of children with ADHD+SOD/CD were found to be more negative (i.e., higher parental stress, more ineffective discipline strategies, more family hassles) than those of controls. These results suggest that the ADHD symptoms that occur with OOD/CD are not associated with deficits in executive functioning and that these symptoms may have environmental rather than neurobiological causes.