title: Does the Environment Have an Enduring Effect on ADHD? A Longitudinal Study of Monozygotic Twin Differences in Children.
abstract: Environmental factors play a key role in the development of Attention-Deficit/Hyperactivity Disorder (ADHD), but the long-term effects of these factors are still unclear. This study analyses data from 1024 monozygotic (identical) twins in Australia, the United States, and Scandinavia who were assessed for ADHD in Preschool, Kindergarten, Grade 1, and Grade 2. Differences within each twin pair were used as a direct measure of non-shared environmental effects. The Trait-State-Occasion (TSO) model developed by Cole et al. (Psychological Methods, 10, 3-20, 2005) was used to separate the non-shared environmental effects into stable factors, and transient factors that excluded measurement error. Stable factors explained, on average, 44 % and 39 % of the environmental variance in hyperactive-impulsive and inattentive symptoms, respectively. Transient effects explained the remaining 56 % and 60 % of variance. The proportion of stable variance was higher than expected based on previous research, suggesting promise for targeted interventions if future research identifies these stable risk factors.
authors.affiliation: School of Behavioural, Cognitive, and Social Sciences, University of New England, Armidale, NSW, Australia. luisa.livingstone@gmail.com.
authors.forename: Luisa T
authors.initials: LT
authors.lastname: Livingstone
authors.affiliation: School of Behavioural, Cognitive, and Social Sciences, University of New England, Armidale, NSW, Australia.
authors.forename: William L
authors.initials: WL
authors.lastname: Coventry
authors.affiliation: Institute for Behavioral Genetics, University of Colorado, Boulder, CO, USA.
authors.forename: Robin P
authors.initials: RP
authors.lastname: Corley
authors.affiliation: Institute for Behavioral Genetics, University of Colorado, Boulder, CO, USA.
authors.forename: Erik G
authors.initials: EG
authors.lastname: Willcutt
authors.affiliation: Department of Behavioral Sciences, Linköping University, Linköping, Sweden.|National Centre for Reading Education and Research, Stavanger University, Stavanger, Norway.
authors.forename: Stefan
authors.initials: S
authors.lastname: Samuelsson
authors.affiliation: Institute for Behavioral Genetics, University of Colorado, Boulder, CO, USA.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Olson
authors.affiliation: School of Behavioural, Cognitive, and Social Sciences, University of New England, Armidale, NSW, Australia.
authors.forename: Brian
authors.initials: B
authors.lastname: Byrne
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000209:etiology* / Q000235:genetics; D002675:Child, Preschool; D004200:Diseases in Twins / Q000209:etiology* / Q000523:psychology; D004777:Environment; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008962:Models, Theoretical; D014430:Twins, Monozygotic / Q000523:psychology*
keywords: ADHD; Environment; Genetics; Longitudinal; Twins