FRIDAY, Feb. 17 (HealthDay News) -- Autism itself seems to be responsible for the problems children with the disorder have in developing motor skills such as running, throwing a ball and learning to write, according to a new study.
Previously, it wasn't clear whether these motor skill difficulties ran in families or were linked to autism, said the researchers at the Washington University School of Medicine in St. Louis.
The investigators studied children from 67 families that had at least one child with autism spectrum disorder and a sibling in the same age group. Twenty-nine families had two children with autism, including six identical twins, and 48 families had only one child with the disorder.
The children were asked to perform a range of motor skills, including push-ups, running, throwing a ball, placing pegs in a pegboard, imitating movements, cutting with scissors and copying forms.
The test results showed that 83 percent of the children with an autism spectrum disorder were below average in motor skills, while their siblings without the disorder generally scored in the normal range, according to the study released online in advance of publication in an upcoming print issue of the journal Autism.
Identical twins had similar scores. Non-twin siblings who each had autism had similar scores. But scores were markedly different in sibling pairs in which one child had autism and the other did not, the researchers found.
"From our results, it looks like motor impairments may be part of the autism diagnosis, rather than a trait genetically carried in the family," lead author Claudia List Hilton, an assistant professor in occupational therapy and an instructor in psychiatry, said in a university news release. "That suggests that motor impairments are a core characteristic of the diagnosis."
And, she said, "the data suggests that genes play a role in the motor impairments observed in those with autism spectrum disorder. This is further evidence that autism spectrum disorder is a largely genetic disorder."
Among children with autism, the lower their motor skills' score, the greater their degree of social impairment and severity of autism.
"Kids who have difficulty with motor skills might have trouble with what we think are simple things like brushing their teeth, buttoning, snapping or starting a zipper -- things that are so basic to being independent, but would cause other problems at school," Hilton said. "They would need to have an aide or someone helping them, and that would set them off as different from the other kids."
While the study uncovered an association between autism and motor impairments, it did not prove a cause-and-effect relationship.
The U.S. National Institute of Neurological Disorders and Stroke has more about autism.
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