Executive and intellectual functions in attention-deficit/hyperactivity disorder with and without comorbidity.
BACKGROUND
Recent neuropsychological theories have targeted deficient executive functions (EF) as the main characteristic of Attention Deficit Hyperactivity Disorder (ADHD), but the nature of the neuropsychological deficits remains elusive and findings are heterogeneous. In particular, it is still unclear whether ADHD subtypes and comorbidity affect intellectual and executive functioning, because large variability has been found in different patient populations. Furthermore, the role of IQ in EF deficits in individuals with ADHD has been debated.


METHODS
The aim of the present research was to study in detail the relationship between EF, ADHD subtypes, and comorbid diagnosis by taking into account the potential role of IQ. For this purpose, 23 children (aged from 5 to 16 years; 20 males and 3 females) with a diagnosis of ADHD were selected.


RESULTS
Data show no differences between children with different subtypes of ADHD on measures of EF, but they evidence differences on EF measures in children with different comorbidities (internalizing versus externalizing disorder). Namely, compared to the internalizing disorders group, the children with externalizing disorders obtained significantly lower scores on different measures of EF (i.e., verbal working memory and categorical fluency), but these differences were strictly dependent on IQ level.


CONCLUSIONS
Comorbidity patterns, rather than ADHD subtypes, appear to be more valid for defining the neuropsychological features of the ADHD endophenotype. Moreover, general intelligence seems to play a substantial role in the cognitive processes underling the disorder, especially in relation to externalizing aspects.
Di Trani
Michela
M
Children's Hospital Bambino Gesù, Rome, Italy.
Casini
Maria Pia
MP
Capuzzo
Francesca
F
Gentile
Simonetta
S
Bianco
Giuseppe
G
Menghini
Deny
D
Vicari
Stefano
S
D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology* / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D003072:Cognition Disorders / Q000453:epidemiology* / Q000503:physiopathology*; D015897:Comorbidity; D056344:Executive Function / Q000502:physiology*; D005260:Female; D006801:Humans; D007360:Intelligence; D008297:Male; D009483:Neuropsychological Tests