ST. LOUIS, Oct. 8 (UPI) -- Language development may be delayed in siblings of children with autism, U.S. researchers suggest.
Researchers at Missouri's Washington University School of Medicine in St. Louis finds mild traits -- not strong enough to provoke a diagnosis of autism -- seem to be present in the siblings of affected children at significantly higher rates than seen in the general population.
The study, published online in advance of print in The American Journal of Psychiatry, finds one in five siblings thought to be unaffected experienced language delays or speech problems early in life. Many female siblings had subtle traits but few had full-blown autism spectrum disorders.
Boys are thought to be affected four times more often than girls by autism, but the study uses standardized methods to account for the presence of quantitative traits -- pegged at a rate more like three affected boys for every two affected girls.
"Mild symptoms, called quantitative traits, may be confounding studies that compare children with autism to their siblings," first author Dr. John Constantino says in a statement. "Researchers presume one child is affected, and the other is not, but our findings suggest that although one child may have autism while the other does not, it's very possible both children are affected to some degree by genes that contribute to autism."