title: Attention-deficit/hyperactivity disorder (ADHD) and motor timing in adolescents and their parents: familial characteristics of reaction time variability vary with age.
abstract: OBJECTIVE
  There is consistent evidence that attention-deficit/hyperactivity disorder (ADHD) is strongly related to impaired motor timing as reflected in decreased accuracy and increased reaction time variability (RTV). It is not known whether motor timing impairments are present in adolescents and adults with ADHD and their unaffected relatives to the same extent as has been reported in children, and whether ADHD and motor timing share familial underpinnings, as reflected in parent-offspring co-segregation and sibling cross-correlations.
  
  
  METHODS
  A total of 589 parents and 808 children/adolescents from families with ADHD and control families (parent/offspring average age: 48.6/17.3 years) were included. All participants were thoroughly assessed for ADHD and performed a 40-trial motor timing task (1-second interval production). Dependent neurocognitive measures included RT median (RTM: representing accuracy), RTV and ex-Gaussian component τ (τ: representing infrequent long response times). Generalized estimating equations were used for analyses.
  
  
  RESULTS
  Unaffected children from families with ADHD had RTV (but not RTM or τ) scores in between those of affected and control children. However, during middle-to-late adolescence, unaffected offspring were not impaired compared to control offspring and differed from ADHD probands, whereas during late adolescence/early adulthood, all offspring groups performed equally. Affected and unaffected parents of families with ADHD showed increased RTV compared to controls, regardless of age (not significant after adjusting for IQ). There were indications for shared familiality between RTV and ADHD as reflected by sibling cross-correlations and between RTM and ADHD as reflected by sibling cross-correlations and a maternal parent-offspring relation (parent-of-origin effect).
  
  
  CONCLUSIONS
  RTV and its familial characteristics are influenced by development during adolescence. Increased RTV in children with ADHD appears to reflect immaturities in their neurocognitive functioning. Maternal ADHD effects might be involved in transmission of RTM (not RTV), but overall RTM showed less compelling (familial) relationships with ADHD than RTV.
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour and Karakter Child and Adolescent Psychiatry University Center, Radboud University Nijmegen Medical Center, the Netherlands. Electronic address: A.Thissen@psy.umcn.nl.
authors.forename: Andrieke J A M
authors.initials: AJ
authors.lastname: Thissen
authors.affiliation: VU University Amsterdam.
authors.forename: Marjolein
authors.initials: M
authors.lastname: Luman
authors.affiliation: University Medical Center Groningen, University of Groningen.
authors.forename: Catharina
authors.initials: C
authors.lastname: Hartman
authors.affiliation: University Medical Center Groningen, University of Groningen.
authors.forename: Pieter
authors.initials: P
authors.lastname: Hoekstra
authors.affiliation: VU University Amsterdam.
authors.forename: Marloes
authors.initials: M
authors.lastname: van Lieshout
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Medical Center.
authors.forename: Barbara
authors.initials: B
authors.lastname: Franke
authors.affiliation: VU University Amsterdam.
authors.forename: Jaap
authors.initials: J
authors.lastname: Oosterlaan
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour and Karakter Child and Adolescent Psychiatry University Center, Radboud University Nijmegen Medical Center, the Netherlands.
authors.forename: Nanda N J
authors.initials: NN
authors.lastname: Rommelse
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour and Karakter Child and Adolescent Psychiatry University Center, Radboud University Nijmegen Medical Center, the Netherlands.
authors.forename: Jan K
authors.initials: JK
authors.lastname: Buitelaar
mesh_terms: D000293:Adolescent; D041923:Adolescent Development / Q000502:physiology*; D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D002648:Child; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D013998:Time Perception / Q000502:physiology*
keywords: ADHD; development; familiality; motor timing; reaction time variability