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A Twin Study

Jane Scourfield, PhD, MRCPsych; Marianne Van den Bree, PhD; Neilson Martin, PhD; Peter McGuffin, PhD, FRCPsych

Arch Gen Psychiatry. 2004;61:489-496.

Background  Evidence supports a genetic influence on conduct problems as a continuous measure of behavior and as a diagnostic category. However, there is a lack of studies using a genetically informative design combined with several different informants and different settings.

Objectives  To examine genetic and environmental influences on conduct problems rated by parent and teacher reports and self-reports and to determine whether their ratings reflect a common underlying phenotype.

Design  A twin study design was used to examine conduct problem scores from ratings by teachers, parents, and twins themselves.

Setting  General community.

Participants  Twins aged 5 to 17 years participating in the Cardiff Study of All Wales and North England Twins (CaStANET) project.

Main Outcome Measures  Conduct problem scale from the Strengths and Difficulties Questionnaire.

Results  Conduct problem scores were significantly heritable based on parent and teacher reports and self-reports. Combining data from all 3 informants showed that they are rating a common underlying phenotype of pervasive conduct problems that is entirely genetic, while teacher ratings show separate genetic influences that are not shared with other raters.

Conclusions  Conduct problems are significantly heritable based on parent and teacher reports and self-reports, and are also influenced by environmental effects that impinge uniquely on children from the same family. There is a cross-situational conduct problems' phenotype, underlying the behavior measured by all informants, that is wholly genetic in origin. No significant influence of shared environmental effects was found.

From the Department of Psychological Medicine, University of Wales College of Medicine, Cardiff. Dr McGuffin is now with the SGDP Research Centre, Institute of Psychiatry, London, England.