title: The dopamine receptor D4 7-repeat allele influences neurocognitive functioning, but this effect is moderated by age and ADHD status: an exploratory study.
abstract: OBJECTIVE
  Evidence suggests the involvement of the dopamine D4 receptor gene (DRD4) in the pathogenesis of ADHD, but the exact mechanism is not well understood. Earlier reports on the effects of DRD4 polymorphisms on neurocognitive and neuroimaging measures are inconsistent. This study investigated the functional consequences of the 7-repeat allele of DRD4 on neurocognitive endophenotypes of ADHD in the Dutch subsample of the International Multicenter ADHD Genetics study.
  
  
  METHODS
  Participants were 350 children (5-11.5 years) and adolescents (11.6-19 years) with ADHD and their 195 non-affected siblings. An overall measure of neuropsychological functioning was derived by principal component analysis from five neurocognitive and five motor tasks. The effects of DRD4 and age were examined using Linear Mixed Model analyses.
  
  
  RESULTS
  The analyses were stratified for affected and non-affected participants after finding a significant three-way interaction between ADHD status, age and the 7-repeat allele. Apart from a main effect of age, a significant interaction effect of age and DRD4 was found in non-affected but not in affected participants, with non-affected adolescent carriers of the 7-repeat allele showing worse neuropsychological performance. In addition, carrying the 7-repeat allele of DRD4 was related to a significantly worse performance on verbal working memory in non-affected siblings, independent of age.
  
  
  CONCLUSIONS
  These results might indicate that the effect of the DRD4 7-repeat allele on neuropsychological functioning is dependent on age and ADHD status.
authors: Department of Psychiatry, Radboud University Nijmegen Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, The Netherlands.
authors: Marieke E
authors: ME
authors: Altink
authors: Nanda N J
authors: NN
authors: Rommelse
authors: Dorine I E
authors: DI
authors: Slaats-Willemse
authors: Alejandro Arias
authors: AA
authors: Vásquez
authors: Barbara
authors: B
authors: Franke
authors: Cathelijne J M
authors: CJ
authors: Buschgens
authors: Ellen A
authors: EA
authors: Fliers
authors: Stephen V
authors: SV
authors: Faraone
authors: Joseph A
authors: JA
authors: Sergeant
authors: Jaap
authors: J
authors: Oosterlaan
authors: Jan K
authors: JK
authors: Buitelaar
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001289:Attention Deficit Disorder with Hyperactivity / Q000235:genetics*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003071:Cognition; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D018598:Minisatellite Repeats; D009483:Neuropsychological Tests; D050638:Receptors, Dopamine D4 / Q000235:genetics*; D035781:Siblings; D055815:Young Adult
chemical_list: C493599:DRD4 protein, human; D050638:Receptors, Dopamine D4