October 8th, 2010
06:10 PM ET
In families in which a child has autism, his or her siblings are more likely to have language delays or speech problems, a new study finds.
The study, to be published in the November issue of the American Journal of Psychiatry, suggests that these siblings have mild symptoms of autism, and that the same genes that contribute to one sibling's full-blown autism may be at fault.
Researchers looked at data from nearly 3,000 children in the United States from more than 1,200 families. These families are in the Interactive Autism Network, a web-based tool to help advance autism research through sharing information.
They found that 20 percent of siblings had some kind of language delay or speech problems early in life, and half of those children had problems that were autistic in nature. Speech patterns characteristic of autism include pronoun reversal - switching "you" and "I," for instance - and invented words.
These siblings also tended to have social abnormalities associated with autism, the authors found. Families with more than one autistic child were more likely to have an additional child with mild autistic symptoms.
This suggests that many children who do not have an autism diagnosis are still affected by the condition, even if only in a mild way, study authors said. In the general population, about 7 percent of children receive a diagnosis of a speech or language disorder, said lead author Dr. John Constantino of Washington University in St. Louis, Missouri.
Many of these children will outgrow or get training to overcome their language problems and have little trace of those abnormalities later in life, Constantino said. But they may provide clues into the mechanism of inheritance of autism in some families.
Further research may reveal what distinguishes children who show this susceptibility to autism but who have been spared the full extent of the condition, he said. This could provide clues into offsetting the disease.
Family history isn't everything, however. There are some families for whom there is no clear inheritance of autism, and no other children seem to have a trace of the disorder, Constantino noted.
Another avenue to explore is the gender ratio in autism. About four boys are thought to have the condition for every one girl with it, but Constantino's study found a ratio of three boys to two girls when including these milder traits. That means that there may be additional girls who benefit from the same kinds of social, psychological, and educational interventions for autism that are more commonly given to boys, Constantino said.
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