title: Genetic and environmental influences on the relationship between ADHD symptoms and internalizing problems: A Chinese twin study.
abstract: Several twin studies have investigated the overlap between attention deficit hyperactivity disorder (ADHD) and externalizing problems; however, limited information is known regarding the genetic and environmental contribution to the overlap between ADHD and internalizing problems. This study examined the genetic and environmental influences on the variation in and covariation between ADHD symptoms and internalizing problems by using the Child Behavior Checklist (CBCL). We investigated 1,316 child and adolescent twins, including 780 monozygotic twins and 536 dizygotic twins, aged 6 years to 18 years from the Chinese Child and Adolescent Twin Registry. ADHD symptoms and internalizing problems were quantified through parent rating by using the Attention Problems Scale and other three scales, which include Anxious/Depressed, Withdrawn, and Somatic Complaints of CBCL. Genetic and environmental susceptibilities common to ADHD symptoms and internalizing problems were examined through bivariate twin modeling. Results showed that genetic factors substantially influenced the ADHD symptoms with a heritability of 72%. Modest genetic influences and substantial shared environmental influences (20-77%) were observed in the three internalizing problem scales. Common genetic and shared environmental influences were essential for the overlap between ADHD and the three internalizing problems respectively. Approximately one-fifth of the genetic variance of ADHD symptoms was shared with anxiety/depression. In conclusion, substantial genetic and shared environmental influences on ADHD symptoms and internalizing problems were observed in Chinese children and adolescents. Our finding supports a common etiology between ADHD and internalizing problems. This finding can also help explain the co-existence of these behavior problems. © 2015 Wiley Periodicals, Inc.
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Health Science Center, Peking University, Beijing, China.
authors.forename: Tian-Jiao
authors.initials: TJ
authors.lastname: Chen
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Health Science Center, Peking University, Beijing, China. jichengye@263.net.
authors.forename: Cheng-Ye
authors.initials: CY
authors.lastname: Ji
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Health Science Center, Peking University, Beijing, China.
authors.forename: Shang-Shang
authors.initials: SS
authors.lastname: Wang
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Paul
authors.initials: P
authors.lastname: Lichtenstein
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Larsson
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Chang
mesh_terms: D000293:Adolescent; D001007:Anxiety / Q000235:genetics; D001008:Anxiety Disorders / Q000235:genetics*; D044466:Asian People / Q000235:genetics; D001289:Attention Deficit Disorder with Hyperactivity / Q000209:etiology / Q000235:genetics*; D002648:Child; D002681:China; D003863:Depression / Q000235:genetics; D004200:Diseases in Twins / Q000235:genetics; D004777:Environment; D005260:Female; D014644:Genetic Variation; D006801:Humans; D008297:Male; D014427:Twins / Q000235:genetics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
keywords: ADHD; CBCL; genetics; internalizing problems; twin study