Research findings suggest that conduct disordered youth have impairments in executive functions (EF), higher-order cognitive abilities mediated by the pre-frontal lobes that regulate purposeful, independent, goal-directed behavior. However, the research examining executive dysfunction among this population has methodological limitations, particularly relating to the selection of samples, control groups, and assessment measures. Most studies have not considered the overlap of comorbid symptoms of Attention Deficit Hyperactivity Disorder (ADHD), a disorder of behavioral inhibition also characterized by executive dysfunction. As a re~ult of not accounting for the high rate of comorbidity of ADHD and Conduct Disorder (CD), the findings of many studies are limited. Thus, it is difficult to discern the actual impact of EF on either CD or ADHD. To date, the extent to which ADHD symptoms impact executive dysfunction in CD youth has not been elucidated adequately. Given the high rate of comorbidity of CD and the cardinal symptoms of ADHD, it is critical to determine the specific sources of neuropsychological dysfunction in adolescents with conduct problems. In this study, the effects of inattention and hyperactive behavior on EF in adolescent delinquents were controlled. The present study compared EF of 67 male juvenile delinquents to those of 67 matched controls. The Delis-Kaplan Executive Function System (D-KEFS), a newly developed test battery of executive functions was utilized. Subjects were matched for age, gender and ethnicity. There were significant differences between juvenile delinquents and controls on six of the eight D-KEFS subtests examined. Juvenile delinquents were found to have significantly lower scores on tasks involving set-shifting, self-regulation, and response inhibition, as well as concept formation, abstract reasoning, and deductive reasoning. However, after controlling for the effects of ADHD, juvenile delinquents were found to have significantly lower performance only on a task involving abstraction and utilization of verbal feedback. After controlling for the effects of estimated IQ, a significant difference between the two groups persisted only for tasks involving set-shifting, self-regulation, and response inhibition with delinquents scoring lower. After controlling for both the effects of ADHD and intelligence, there were no significant differences in executive EF performance between juvenile delinquents and non-delinquent controls.
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