caa a22 4500 388058951 CHVBK 20180307125115.0 cr unu---uuuuu 161130e19980201xx s 000 0 eng 10.1375/twin.1.1.25 doi S1369052300000209 pii (NATIONALLICENCE)cambridge-10.1375/twin.1.1.25 Quantitative genetic analysis of Internalising and Externalising Problems in a large sample of 3-year-old twins [Elektronische Daten] For a quantitative genetic study of pre-school problem behaviours, we have collected data with the Child Behavior Checklist for 2 and 3-year-old children (CBCL 2/3). Questionnaires were completed by mothers of 3620 twin pairs: 633 monozygotic males, 581 dizygotic males, 695 monozygotic females, 519 dizygotic females and 1192 dizygotic opposite sex twin pairs. The genetic and environmental influences on the Externalising and Internalising Problem scales were estimated, simultaneously with sex differences and sibling interaction effects. Genetic factors explained most of the observed variance for both Externalising and Internalising Problems. Cooperative sibling interactions were found for Externalising Problems, indicating that twins reinforce each other's behaviour. Sex differences in genetic architecture were found for Externalising Problems. Genetic factors explained 75% of the variance in girls and 50% in boys. Shared environmental influences were only of importance in boys. For both problem scales, non-shared environmental factors accounted for 25 to 32% of the variance. The observed variances of Internalising Problems could be adequately explained by genetic and nonshared environmental factors, with genetic factors accounting for 68% of the variance. Copyright © Cambridge University Press 1998 pre-school children nationallicence problem behaviour nationallicence Child Behavior Checklist nationallicence twins nationallicence behaviour genetics nationallicence van der Valk JC Department of Child and Adolescent Psychiatry, Sophia Children's Hospital, Rotterdam, The Netherlands; Department of Psychonomics, Free University, Amsterdam, The Netherlands. vandervalk@psys.azr.nl Verhulst FC Department of Child and Adolescent Psychiatry, Sophia Children's Hospital, Rotterdam, The Netherlands. Stroet TM Department of Psychonomics, Free University, Amsterdam, The Netherlands. Boomsma DI Department of Psychonomics, Free University, Amsterdam, The Netherlands. Twin Research Cambridge University Press 1/1(1998-02-01), 25-33 1369-0523 1:1<25 1998 1 THG https://doi.org/10.1375/twin.1.1.25 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1375/twin.1.1.25 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- van der Valk JC Department of Child and Adolescent Psychiatry, Sophia Children's Hospital, Rotterdam, The Netherlands; Department of Psychonomics, Free University, Amsterdam, The Netherlands. vandervalk@psys.azr.nl NATIONALLICENCE 700 1- Verhulst FC Department of Child and Adolescent Psychiatry, Sophia Children's Hospital, Rotterdam, The Netherlands NATIONALLICENCE 700 1- Stroet TM Department of Psychonomics, Free University, Amsterdam, The Netherlands NATIONALLICENCE 700 1- Boomsma DI Department of Psychonomics, Free University, Amsterdam, The Netherlands NATIONALLICENCE 773 0- Twin Research Cambridge University Press 1/1(1998-02-01), 25-33 1369-0523 1:1<25 1998 1 THG CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge