title: Reaction time performance in ADHD: improvement under fast-incentive condition and familial effects.
abstract: BACKGROUND
  Reaction time (RT) variability is one of the strongest findings to emerge in cognitive-experimental research of attention deficit hyperactivity disorder (ADHD). We set out to confirm the association between ADHD and slow and variable RTs and investigate the degree to which RT performance improves under fast event rate and incentives. Using a group familial correlation approach, we tested the hypothesis that there are shared familial effects on RT performance and ADHD.
  
  
  METHODS
  A total of 144 ADHD combined-type probands, 125 siblings of the ADHD probands and 60 control participants, ages 6-18, performed a four-choice RT task with baseline and fast-incentive conditions.
  
  
  RESULTS
  ADHD was associated with slow and variable RTs, and with greater improvement in speed and RT variability from baseline to fast-incentive condition. RT performance showed shared familial influences with ADHD. Under the assumption that the familial effects represent genetic influences, the proportion of the phenotypic correlation due to shared familial influences was estimated as 60-70%.
  
  
  CONCLUSIONS
  The data are inconsistent with models that consider RT variability as reflecting a stable cognitive deficit in ADHD, but instead emphasize the extent to which energetic or motivational factors can have a greater effect on RT performance in ADHD. The findings support the role of RT variability as an endophenotype mediating the link between genes and ADHD.
authors.affiliation: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, UK.
authors.forename: Penny
authors.initials: P
authors.lastname: Andreou
authors.forename: Ben M
authors.initials: BM
authors.lastname: Neale
authors.forename: Wai
authors.initials: W
authors.lastname: Chen
authors.forename: Hanna
authors.initials: H
authors.lastname: Christiansen
authors.forename: Isabel
authors.initials: I
authors.lastname: Gabriels
authors.forename: Alexander
authors.initials: A
authors.lastname: Heise
authors.forename: Sheera
authors.initials: S
authors.lastname: Meidad
authors.forename: Ueli C
authors.initials: UC
authors.lastname: Muller
authors.forename: Henrik
authors.initials: H
authors.lastname: Uebel
authors.forename: Tobias
authors.initials: T
authors.lastname: Banaschewski
authors.forename: Iris
authors.initials: I
authors.lastname: Manor
authors.forename: Robert
authors.initials: R
authors.lastname: Oades
authors.forename: Herbert
authors.initials: H
authors.lastname: Roeyers
authors.forename: Aribert
authors.initials: A
authors.lastname: Rothenberger
authors.forename: Pak
authors.initials: P
authors.lastname: Sham
authors.forename: Hans-Christoph
authors.initials: HC
authors.lastname: Steinhausen
authors.forename: Philip
authors.initials: P
authors.lastname: Asherson
authors.forename: Jonna
authors.initials: J
authors.lastname: Kuntsi
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000235:genetics* / Q000523:psychology; D002648:Child; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D008297:Male; D008957:Models, Genetic; D009042:Motivation; D010641:Phenotype; D011930:Reaction Time / Q000235:genetics*; D035781:Siblings; D013223:Statistics as Topic