title: Genetic influences on the stability of attention-deficit/hyperactivity disorder symptoms from early to middle childhood.
abstract: BACKGROUND
  The high heritability of the core symptoms of attention-deficit/hyperactivity disorder (ADHD) has been repeatedly demonstrated, but few studies to date have investigated the extent to which the same genetic influences operate across development or new genes emerge at different developmental periods.
  
  
  METHODS
  We report data from a large, population-based study of approximately 4,000 twin pairs, who have been followed up from early to middle childhood.
  
  
  RESULTS
  Parents' ratings of ADHD symptoms showed moderate stability across the ages, which was mainly due to shared genetic influences. There was also evidence of additional genetic influences, which were not shared with those acting earlier on, emerging at later age periods. The contribution of environmental influences to the stability of the ADHD symptoms over time was small. Parents' ratings on the Conners' DSM-IV ADHD subscale at the last assessment point, at an average age of 8 years, did not show the rater contrast effects that were observed in the parents' ratings at earlier ages with briefer measures. Similar estimates of genetic and environmental influences were obtained for girls and boys.
  
  
  CONCLUSIONS
  We discuss the implications of the findings for molecular genetic studies on ADHD symptomatology.
authors.affiliation: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, London, United Kingdom. j.kuntsi@iop.kcl.ac.uk
authors.forename: Jonna
authors.initials: J
authors.lastname: Kuntsi
authors.forename: Frühling
authors.initials: F
authors.lastname: Rijsdijk
authors.forename: Angelica
authors.initials: A
authors.lastname: Ronald
authors.forename: Philip
authors.initials: P
authors.lastname: Asherson
authors.forename: Robert
authors.initials: R
authors.lastname: Plomin
mesh_terms: D000367:Age Factors; D019958:Attention Deficit and Disruptive Behavior Disorders / Q000453:epidemiology* / Q000235:genetics*; D002648:Child; D002653:Child Behavior Disorders / Q000235:genetics; D003430:Cross-Sectional Studies; D004200:Diseases in Twins / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008957:Models, Genetic; D015588:Observer Variation; D010552:Personality Assessment; D011569:Psychiatric Status Rating Scales; D012044:Regression Analysis; D012189:Retrospective Studies; D012737:Sex Factors; D012931:Social Environment; D018433:Twin Studies as Topic