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Epidemiology of Multiple-, Single-Child Autism Described

Single, multiple incidence of autism in families may have differing genetic bases

FRIDAY, Oct. 15 (HealthDay News) -- Though some families have a single child with autism spectrum disorder, other families have multiple autistic children or otherwise normal children with some autistic traits, suggesting differing genetic bases for the condition, according to a study published Oct. 1 in The American Journal of Psychiatry.

John N. Constantino, M.D., of the Washington University School of Medicine in St. Louis, and colleagues analyzed data from the Interactive Autism Network on 2,920 children (ages 4 to 18) from 1,235 families. The data included a parent's characterizations of autistic symptoms in each child in the family collected using the Social Responsiveness Scale.

The analysis found that in 10.9 percent of families with an autistic child, traditionally defined autism occurred in an additional child. Furthermore, 20 percent of siblings without an autism diagnosis had language delay, and half of those children exhibited speech patterns characteristic of autism. Finally, the analysis revealed a range of subclinical autistic traits among children in families with multiple autistic children, but there was a comparative absence of the traits in single-incidence families.

"These data suggest that, depending on how it is defined, sibling recurrence in autism spectrum disorder may exceed previously published estimates and varies as a function of family type. The results support differences in mechanisms of genetic transmission between simplex and multiplex autism and advance current understanding of the genetic epidemiology of autism spectrum conditions," the authors write.

One study author receives royalties for the commercial distribution of the Social Responsiveness Scale used in this study, which was provided at no cost for this study. Another author has been a consultant to Shire Development Inc.

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