Cognitive impairments in attention deficit hyperactivity disorder: the role of subtype symptomology
LE3 .A278 2005
Master of Science
The current study was designed to assess the cognitive deficits of children with different Attention Deficit Hyperactivity Disorder (ADHD) subtypes. Teachers rated 154 clinic-referred children using the Conners' Teacher Rating Scale. Teacher ratings were then used to form four groups: ADHD inattentive (ADHD-I; ' n' = 47), ADHD hyperactive/impulsive (ADHD-HI; 'n' = 19), ADHD combined (ADHD-C; 'n' = 50), and a clinical control group ('n' = 38). The four groups were compared on five factors: a Phonological Processing factor, a Working Memory factor, a Sustained Attention factor, CPT commissions T-score, and the CPT time estimation. The groups were found to differ on the Working Memory factor, with the ADHD-I performing significantly worse than the three other groups. In a secondary analysis, participants with t-scores on the hyperactive/impulsive subscale that were close to the cut-off of 65 (60-64) were eliminated from the ADHD-I group. This allowed for a better controlled sample and ensured that the ADHD-I children were not better described as having ADHD-HI. It was found that the groups did not differ significantly in this analysis which may be attribute to the loss of power caused by eliminating participants. Lastly, a clinician diagnosed learning disabled (LD) group (' n' = 13) was added to determine the utility of the Reading and Working Memory factors in differential diagnosis. The results of this analysis indicated that the Reading and Working Memory factors were not able to distinguish the ADHD-I group from the LD group. Measures that can reliably distinguish ADHD-I from LD are essential for differential diagnosis and should be the focus of future research. Based on these results, more studies on measures of working memory are recommended, as these measures may be able to separate ADHD-C and ADHD-HI from ADHD-I.
The author grants permission to the University Librarian at Acadia University to reproduce, loan or distribute copies of my thesis in microform, paper or electronic formats on a non-profit basis. The author retains the copyright of the thesis.