title: Performance variability, impulsivity errors and the impact of incentives as gender-independent endophenotypes for ADHD.
abstract: BACKGROUND
  Attention-deficit hyperactivity disorder (ADHD) is one of the most common and highly heritable child psychiatric disorders. There is strong evidence that children with ADHD show slower and more variable responses in tasks such as Go/Nogo tapping aspects of executive functions like sustained attention and response control which may be modulated by motivational factors and/or state-regulation processes. The aim of this study was (1) to determine if these executive functions may constitute an endophenotype for ADHD; (2) to investigate for the first time whether known modulators of these executive functions may also be familial; and (3) to explore whether gender has an impact on these measures.
  
  
  METHODS
  Two hundred and five children with ADHD combined type, 173 nonaffected biological siblings and 53 controls with no known family history of ADHD were examined using a Go/Nogo task in the framework of a multi-centre study. Performance-measures and modulating effects of event-rate and incentives were examined. Shared familial effects on these measures were assessed, and the influence of gender was tested.
  
  
  RESULTS
  Children with ADHD responded more slowly and variably than nonaffected siblings or controls. Nonaffected siblings showed intermediate scores for reaction-time variability, false alarms and omission errors under fast and slow event-rates. A slower event-rate did not lead to reduced performance specific to ADHD. In the incentive condition, mean reaction-times speeded up and became less variable only in children with ADHD and their nonaffected siblings, while accuracy was improved in all groups. Males responded faster, but also committed more false alarms. There were no interactions of group by gender.
  
  
  CONCLUSIONS
  Reaction-time variability and accuracy parameters could be useful neuropsychological endophenotypes for ADHD. Performance-modulating effects of incentives suggested a familially driven motivational dysfunction which may play an important role on etiologic pathways and treatment approaches for ADHD. The effects of gender were independent of familial effects or ADHD-status, which in turn suggests that the proposed endophenotypes are independent of gender.
authors.affiliation: Child & Adolescent Psychiatry, University of Göttingen, von Siebold-Strasse 5, Göttingen, Germany. huebel@gwdg.de
authors.forename: Henrik
authors.initials: H
authors.lastname: Uebel
authors.forename: Björn
authors.initials: B
authors.lastname: Albrecht
authors.forename: Philip
authors.initials: P
authors.lastname: Asherson
authors.forename: Norbert A
authors.initials: NA
authors.lastname: Börger
authors.forename: Louise
authors.initials: L
authors.lastname: Butler
authors.forename: Wai
authors.initials: W
authors.lastname: Chen
authors.forename: Hanna
authors.initials: H
authors.lastname: Christiansen
authors.forename: Alexander
authors.initials: A
authors.lastname: Heise
authors.forename: Jonna
authors.initials: J
authors.lastname: Kuntsi
authors.forename: Ulrike
authors.initials: U
authors.lastname: Schäfer
authors.forename: Penny
authors.initials: P
authors.lastname: Andreou
authors.forename: Iris
authors.initials: I
authors.lastname: Manor
authors.forename: Rafaela
authors.initials: R
authors.lastname: Marco
authors.forename: Ana
authors.initials: A
authors.lastname: Miranda
authors.forename: Aisling
authors.initials: A
authors.lastname: Mulligan
authors.forename: Robert D
authors.initials: RD
authors.lastname: Oades
authors.forename: Jaap
authors.initials: J
authors.lastname: van der Meere
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Faraone
authors.forename: Aribert
authors.initials: A
authors.lastname: Rothenberger
authors.forename: Tobias
authors.initials: T
authors.lastname: Banaschewski
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology*; D002648:Child; D003072:Cognition Disorders / Q000175:diagnosis / Q000453:epidemiology*; D007174:Disruptive, Impulse Control, and Conduct Disorders / Q000453:epidemiology* / Q000523:psychology; D056344:Executive Function; D005260:Female; D006801:Humans; D008297:Male; D009042:Motivation; D009483:Neuropsychological Tests; D010641:Phenotype; D011930:Reaction Time; D012737:Sex Factors