Executive and intellectual functions in attention-deficit/hyperactivity disorder with and without comorbidity

Michela Di Trani, Maria Pia Casini, Francesca Capuzzo, Simonetta Gentile, Giuseppe Bianco, Deny Menghini, Stefano Vicari

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)462-469
Number of pages8
JournalBrain and Development
Issue number6
Publication statusPublished - Jun 2011


  • ADHD
  • Comorbid diagnosis
  • Executive function
  • Intelligence quotient

ASJC Scopus subject areas

  • Clinical Neurology
  • Developmental Neuroscience
  • Pediatrics, Perinatology, and Child Health


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