This study used prospective longitudinal data from multiple sources including parent and teacher report and laboratory assessment. It included a measure of impairment which is required for diagnosis but not often included in studies assessing changes in severity. Additionally, neuropsychological functioning was assessed using the NEPSY, which allowed for continuity of longitudinal measurement along with age- and gender-specific norms that enable comparison to other samples of children. The use of trained evaluators who were blind to clinical data, enhanced the validity of our findings and reducing the likelihood of reporter bias. Finally, SEM provided a stringent test of the longitudinal association between ADHD severity and neuropsychological functioning and made a statistical comparison of the paths between the two groups possible.
