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Res Autism Spectr Disord. 2008 Apr 1;2(2):320-331.

Genetic and Environmental Influences on Symptom Domains in Twins and Siblings with Autism.

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Drs. Mazefsky, Riley, and Maes were in the Virginia Institute for Psychiatric and Behavioral Genetics at Virginia Commonwealth University at the time of the study. Dr. Mazefsky is now in the Departments of Pediatrics and Psychiatry at the University of Pittsburgh. Dr. Goin-Kochel is in the Department of Molecular and Human Genetics at Baylor College of Medicine. Send reprint requests to Carla Mazefsky, 3705 5th Ave, Child Development Unit, Children's Hospital of Pittsburgh, Pittsburgh, PA 15213; 412-692-6520;


Clarifying the sources of variation among autism symptom domains is important to the identification of homogenous subgroups for molecular genetic studies. This study explored the genetic and environmental bases of nonverbal communication and social interaction, two symptom domains that have also been related to treatment response, in 1294 child and adolescent twins and siblings with pervasive developmental disorders (PDDs) from the Autism Genetic Resource Exchange under the age of 18. Twin/sibling resemblance was assessed through correlations and behavior genetic modeling of Autism Diagnostic Interview (ADI) nonverbal communication and social scores. Variation in these phenotypes was explained by additive genetic, dominant genetic, and unique environmental factors with no evidence for shared environmental factors. Broad heritability estimates were higher for nonverbal communication (45%) than social interaction (28%). Nonverbal communication and social scores were partially accounted for by the same underlying genetic and environmental factors. Gender differences were not supported. These results add to information on familial resemblance of these symptom domains based on correlational methods, and this study is one of the first to apply behavioral genetic modeling to a PDD population. The results have implications for molecular genetics as well as treatment.

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