title: Does IQ influence associations between ADHD symptoms and other cognitive functions in young preschoolers?
abstract: BACKGROUND
  Working memory, inhibition, and expressive language are often impaired in ADHD and many children with ADHD have lower IQ-scores than typically developing children. The aim of this study was to test whether IQ-score influences associations between ADHD symptoms and verbal and nonverbal working memory, inhibition, and expressive language, respectively, in a nonclinical sample of preschool children.
  
  
  METHODS
  In all, 1181 children recruited from the Norwegian Mother and Child Cohort Study were clinically assessed at the age of 36 to 46 months. IQ-score and working memory were assessed with subtasks from the Stanford Binet test battery, expressive language was reported by preschool teachers (Child Development Inventory), response inhibition was assessed with a subtask from the NEPSY test, and ADHD symptoms were assessed by parent interview (Preschool Age Psychiatric Assessment).
  
  
  RESULTS
  The results showed an interaction between ADHD symptoms and IQ-score on teacher-reported expressive language. In children with below median IQ-score, a larger number of ADHD symptoms were more likely to be accompanied by reports of lower expressive language skills, while the level of ADHD symptoms exerted a smaller effect on reported language skills in children with above median IQ-score. The associations between ADHD symptoms and working memory and response inhibition, respectively, were not influenced by IQ-score.
  
  
  CONCLUSIONS
  Level of IQ-score affected the relation between ADHD symptoms and teacher-reported expressive language, whereas associations between ADHD symptoms and working memory and response inhibition, respectively, were significant and of similar sizes regardless of IQ-score. Thus, in preschoolers, working memory and response inhibition should be considered during an ADHD assessment regardless of IQ-score, while language skills of young children are especially important to consider when IQ-scores are average or low.
authors.affiliation: Division of Mental Health, Norwegian Institute of Public Health, Oslo, Norway. ninamarit.rohrer-baumgartner@fhi.no.
authors.forename: Nina
authors.initials: N
authors.lastname: Rohrer-Baumgartner
authors.forename: Pål
authors.initials: P
authors.lastname: Zeiner
authors.forename: Jens
authors.initials: J
authors.lastname: Egeland
authors.forename: Kristin
authors.initials: K
authors.lastname: Gustavson
authors.forename: Annette Holth
authors.initials: AH
authors.lastname: Skogan
authors.forename: Ted
authors.initials: T
authors.lastname: Reichborn-Kjennerud
authors.forename: Heidi
authors.initials: H
authors.lastname: Aase
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology / Q000523:psychology*; D002675:Child, Preschool; D003071:Cognition / Q000502:physiology*; D005260:Female; D006801:Humans; D007360:Intelligence / Q000502:physiology*; D007802:Language; D008137:Longitudinal Studies; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009483:Neuropsychological Tests