title: Nonshared environmental influences on individual differences in early behavioral development: a monozygotic twin differences study.
abstract: The monozygotic (MZ) twin differences method was used to investigate nonshared environmental (NSE) influences independent of genetics. Four-year-old MZ twin pairs (N = 2,353) were assessed by their parents on 2 parenting measures (harsh parental discipline and negative parental feelings) and 4 behavioral measures (anxiety, prosocial behavior, hyperactivity, and conduct problems). Within-pair differences in parenting correlated significantly with MZ differences in behavior, with an average effect size of 3%. For the extreme 10% of the parenting-discordant and behavior-discordant distributions, the average NSE effect size was substantially greater (11%), suggesting a stronger NSE relationship for more discordant twins. NSE relationships were also stronger in higher risk environments, that is, families with lower socioeconomic status, greater family chaos, or greater maternal depression.
authors.affiliation: Social, Genetic, and Developmental Psychiatry Research Centre, Institute of Psychiatry, King's College London, UK. spjgkaa@iop.kcl.ac.uk
authors.forename: Kathryn
authors.initials: K
authors.lastname: Asbury
authors.forename: Judith F
authors.initials: JF
authors.lastname: Dunn
authors.forename: Alison
authors.initials: A
authors.lastname: Pike
authors.forename: Robert
authors.initials: R
authors.lastname: Plomin
mesh_terms: D002648:Child; D002652:Child Behavior / Q000523:psychology; D002657:Child Development; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D012919:Social Behavior; D012931:Social Environment; D011795:Surveys and Questionnaires; D014430:Twins, Monozygotic / Q000523:psychology*