title: Attention problems and attention-deficit/hyperactivity disorder in discordant and concordant monozygotic twins: evidence of environmental mediators.
abstract: OBJECTIVE
  To study familial and nonfamilial environmental influences on attention problems and attention-deficit/hyperactivity disorder (ADHD) in monozygotic twins discordant and concordant-high and low for these traits.
  
  
  METHODS
  Ninety-five twin pairs from The Netherlands Twin Register were selected. Longitudinal survey data were collected at 1, 2, 3, 5, 7, 10, and 12 years from parents, twins, and teachers. Mothers participated in a structured clinical interview when twins were between 10 and 17 years of age.
  
  
  RESULTS
  Affected twins from discordant pairs scored higher than unaffected cotwins on multiple measures of attention problems, ADHD, and other behavior problems according to mother, teacher, and self. Behavioral discordance was evident at age 2 and all subsequent measurements. Compared with unaffected cotwins, affected twins had lower birth weight and delayed physical growth and motor development. Differences between discordant and concordant groups were reported for maternal smoking, sleeping in different rooms, and living with only one parent.
  
  
  CONCLUSIONS
  Significant markers of ADHD are found in infancy and include low birth weight and delayed motor development. As the knowledge of specific genetic and environmental influences on ADHD increases, future studies may focus on their complex interplay.
authors.affiliation: Ms. Lehn, Ms. Derks, and Drs. van Beijsterveldt and Boomsma are with the Department of Biological Psychology, and Dr. Heutink is with the Centre for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands; Dr. Hudziak is with the Division of Human Genetics, Center for Children, Youth and Families, and the University of Vermont, Burlington; Ms. Lehn is also with the Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Hanne
authors.initials: H
authors.lastname: Lehn
authors.affiliation: Ms. Lehn, Ms. Derks, and Drs. van Beijsterveldt and Boomsma are with the Department of Biological Psychology, and Dr. Heutink is with the Centre for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands; Dr. Hudziak is with the Division of Human Genetics, Center for Children, Youth and Families, and the University of Vermont, Burlington; Ms. Lehn is also with the Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Eske M
authors.initials: EM
authors.lastname: Derks
authors.affiliation: Ms. Lehn, Ms. Derks, and Drs. van Beijsterveldt and Boomsma are with the Department of Biological Psychology, and Dr. Heutink is with the Centre for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands; Dr. Hudziak is with the Division of Human Genetics, Center for Children, Youth and Families, and the University of Vermont, Burlington; Ms. Lehn is also with the Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: James J
authors.initials: JJ
authors.lastname: Hudziak
authors.affiliation: Ms. Lehn, Ms. Derks, and Drs. van Beijsterveldt and Boomsma are with the Department of Biological Psychology, and Dr. Heutink is with the Centre for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands; Dr. Hudziak is with the Division of Human Genetics, Center for Children, Youth and Families, and the University of Vermont, Burlington; Ms. Lehn is also with the Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Peter
authors.initials: P
authors.lastname: Heutink
authors.affiliation: Ms. Lehn, Ms. Derks, and Drs. van Beijsterveldt and Boomsma are with the Department of Biological Psychology, and Dr. Heutink is with the Centre for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands; Dr. Hudziak is with the Division of Human Genetics, Center for Children, Youth and Families, and the University of Vermont, Burlington; Ms. Lehn is also with the Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Toos C E M
authors.initials: TCEM
authors.lastname: van Beijsterveldt
authors.affiliation: Ms. Lehn, Ms. Derks, and Drs. van Beijsterveldt and Boomsma are with the Department of Biological Psychology, and Dr. Heutink is with the Centre for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands; Dr. Hudziak is with the Division of Human Genetics, Center for Children, Youth and Families, and the University of Vermont, Burlington; Ms. Lehn is also with the Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.. Electronic address: dorret@psy.vu.nl.
authors.forename: Dorret I
authors.initials: DI
authors.lastname: Boomsma
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D012042:Registries; D012307:Risk Factors; D012720:Severity of Illness Index; D012931:Social Environment; D014430:Twins, Monozygotic