The neuropsychological phenotype of attention deficit hyperactivity disorder: are there differences among subtypes?

INTRODUCTION: Recent studies suggest that the ADHD subtypes would be best conceptualized as separate clinical entities, based on their epidemiology, central and associate symptomatology. OBJECTIVES: To determine the differences and similarities between subtypes in its associate symptomatology, specifically in the neuropsychological phenotype of executive dysfunction. PATIENTS AND METHODS: A group of children between 6 and 14 years of age with a diagnosis of ADHD-innattentive subtype (DESAT, n = 20) and another with ADHD-combined subtype (COMB, n = 39). RESULTS: Overall, the COMB subject sample displayed lower performance than DESAT group. Statistically significant differences were found in Kaufman-ABC-hands movement subtest, Wisconsin Card Sorting Test (WCST)-total error and WCST-conceptual level. CONCLUSIONS: The subtypes differ significantly in measures or non verbal working memory, hindsight, foresight, and motor control. Both groups share a deficit in response output speed and verbal working memory. We hypothesized areas of cognitive superiority for each subtype: spatial memory for the inattentive and gestaltic composition for the combined. Results provide evidence to support quantitative and qualitative differences in the neuropsychological profile between the ADHD-innatentive and combined subtypes.