Separation of genetic influences on attention deficit hyperactivity disorder symptoms and reaction time performance from those on IQ

• Published in: Psychological medicine 2010-06, Vol.40 (6), p.1027-1037
• Main Authors: Wood, A. C., Asherson, P., van der Meere, J. J., Kuntsi, J.
• Format: Article
• Language: English
• Subjects: ADHD; Attention; Attention Deficit Disorder with Hyperactivity - diagnosis; Attention Deficit Disorder with Hyperactivity - genetics; Attention Deficit Disorder with Hyperactivity - psychology; Attention deficit disorders. Hyperactivity; Attention deficit hyperactivity disorder; Biological and medical sciences; Child; Child clinical studies; Cognition & reasoning; Cohort Studies; Diseases in Twins - diagnosis; Diseases in Twins - genetics; Diseases in Twins - psychology; England; Female; Genetic factors; Genetics; Humans; Intelligence; Intelligence - genetics; Intelligence quotient; Male; Medical sciences; Models, Genetic; Models, Statistical; Multivariate Analysis; Neuropsychological Tests - statistics & numerical data; Phenotype; Psychology. Psychoanalysis. Psychiatry; Psychometrics; Psychopathology. Psychiatry; reaction time; Reaction Time - genetics; reaction time variability; Reaction times; Response time; Symptoms; Twins, Dizygotic - genetics; Twins, Dizygotic - psychology; Twins, Monozygotic - genetics; Twins, Monozygotic - psychology; Variability; Wales
• ISSN: 0033-2917; 1469-8978; 1469-8978
• DOI: 10.1017/S003329170999119X

Attention deficit hyperactivity disorder (ADHD) shows a strong phenotypic and genetic association with reaction time (RT) variability, considered to reflect lapses in attention. Yet we know little about whether this aetiological pathway is shared with other affected cognitive processes in ADHD, such as lower IQs or the generally slower responses (mean RTs). We aimed to address the question of whether a shared set of genes exist that influence RT variability, mean RT, IQ and ADHD symptom scores, or whether there is evidence of separate aetiological pathways. Multivariate structural equation modelling on cognitive tasks data (providing RT data), IQ and ADHD ratings by parents and teachers collected on general population sample of 1314 twins, at ages 7-10 years. Multivariate structural equation models indicated that the shared genetic influences underlying both ADHD symptom scores and RT variability are also shared with those underlying mean RT, with both types of RT data largely indexing the same underlying liability. By contrast, the shared genetic influences on ADHD symptom scores and RT variability (or mean RT) are largely independent of the genetic influences that ADHD symptom scores share with IQ. The finding of unique aetiological pathways between IQ and RT data, but shared components between mean RT, RT variability and ADHD symptom scores, illustrates key influences in the genetic architecture of the cognitive and energetic processes that underlie the behavioural symptoms of ADHD. In addition, the multivariate genetic model fitting findings provide valuable information for future molecular genetic analyses.