title: High heritability for a composite index of children's activity level measures.
abstract: Despite the high heritability of children's activity level, which forms part of the core symptom domain of hyperactivity-impulsivity within attention deficit hyperactivity disorder (ADHD), there has only been a limited success with identifying candidate genes involved in its etiology. This may reflect a lack of understanding about the different measures used to define activity level across studies. We aimed to study the genetic and environmental etiology across three measures of activity level: parent and teacher ratings of hyperactivity-impulsivity and actigraph measurements, within a population-based sample of 463 7-9 year old twin pairs. We further examined ways in which the three measures could be combined for future molecular studies. Phenotypic correlations across measures were modest, but a common underlying phenotypic factor was highly heritable (92%); as was a simple aggregation of all three measurements (77%). This suggests that distilling what is common to all three measures may be a good method for generating a quantitative trait suitable for molecular studies of activity level in children. The high heritabilities found are encouraging in this respect.
authors.affiliation: Social, Genetic and Developmental Psychiatry, Institute of Psychiatry, P.O. Box 80, De Crespigny Park, London SE5 8AF, UK. alexis.wood@iop.kcl.ac.uk
authors.forename: Alexis C
authors.initials: AC
authors.lastname: Wood
authors.forename: Frühling
authors.initials: F
authors.lastname: Rijsdijk
authors.forename: Kimberly J
authors.initials: KJ
authors.lastname: Saudino
authors.forename: Philip
authors.initials: P
authors.lastname: Asherson
authors.forename: Jonna
authors.initials: J
authors.lastname: Kuntsi
mesh_terms: D019958:Attention Deficit and Disruptive Behavior Disorders / Q000235:genetics*; D002648:Child; D005192:Family Health; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007175:Impulsive Behavior / Q000235:genetics*; D008297:Male; D008957:Models, Genetic; D015233:Models, Statistical; D009043:Motor Activity; D015999:Multivariate Analysis; D010290:Parents; D010641:Phenotype