The etiology of autistic traits in preschoolers: a population-based twin study

E.L. de Zeeuw, Catharina E M van Beijsterveldt, Rosa A Hoekstra, Meike Bartels, Dorret I Boomsma

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BACKGROUND: Autism Spectrum Disorders (ASD) are highly heritable, but the exact etiological mechanisms underlying the condition are still unclear.

METHODS: Using a multiple rater twin design in a large sample of general population preschool twins, this study aimed to (a) estimate the contribution of genetic and environmental factors to autistic traits, controlling for the possible effects of rater bias, (b) to explore possible sex differences in etiology and (c) to investigate the discordance in autistic traits in monozygotic and same-sex dizygotic twin pairs. The Netherlands Twin Register collected maternal and paternal ratings on autistic traits from a general population of 38,798 three-year-old twins. Autistic traits were assessed with the DSM-oriented Pervasive Developmental Problems scale of the Child Behavior Check List for preschoolers (1½-5 years).

RESULTS: Mother and fathers showed high agreement in their assessment of autistic traits (r = .60-.66). Differences between children in autistic traits were largely accounted for by genetic effects (boys: 78% and girls: 83%). Environmental effects that are unique to a child also played a modest role. Environmental effects shared by children growing up in the same family were negligible, once rater bias was controlled for. While the prevalence for clinical ASD is higher in boys than in girls, this study did not find evidence for striking differences in the etiology of autistic traits across the sexes. Even though the heritability was high, 29% of MZ twin pairs were discordant for high autistic traits (clinical range vs. normal development), suggesting that despite high genetic risk, environmental factors might lead to resilience, unaffected status in the context of genetic risk, in some children.

CONCLUSIONS: It is important to focus future research on risk factors that might interplay with a genetic disposition for ASD, but also on protective factors that make a difference in the lives of children at genetic risk.

Original languageEnglish
Pages (from-to)893-901
Number of pages9
JournalJournal of Child Psychology and Psychiatry
Issue number8
Early online date19 May 2017
Publication statusPublished - Aug 2017


The authors are grateful to the twin families and the teachers for their participation. The authors acknowledge research program ‘Consortium on Individual Development (CID)’ which is funded through the Gravitation program of the Dutch Ministry of Education, Culture and Science and the Netherlands Organization for Scientific Research (NWO 0240-001-003); ‘Twin-family database for behavior genetics and genomics studies’ (NWO 480-04-004); Twin-family study of individual differences in school achievement’ (NWO: 056-32-010); ‘KNAW Academy Professor Award (PAH/6635)’; ‘Genetic influences on stability and change in psychopathology from childhood to young adulthood’ (NWO/ZonMW 91210020). The authors have declared that they have no competing or potential conflicts of interest.

FundersFunder number
Ministerie van Onderwijs, Cultuur en Wetenschap
Nederlandse Organisatie voor Wetenschappelijk Onderzoek0240-001-003, PAH/6635, NWO 480-04-004, 056-32-010, NWO/ZonMW 91210020


    • Journal Article

    Cohort Studies

    • Netherlands Twin Register (NTR)


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