In the largest ever look at the DNA of children with autism, scientists said Wednesday they found new genetic variants associated with the disorder that often are not present in the children’s parents.

The findings published online in the journal Nature suggest that autism may be the result of several different genetic changes that are not necessarily shared among people with the diagnosis, even though they have similar symptoms.

Researchers at institutions around the globe looked at blood samples from 1,000 elementary school children with autism and 1,300 without.

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“We found many more disrupted genes in the autistic children than in the control group,” said Dr. Stanley Nelson, a professor of human genetics and psychiatry at the University of California, Los Angeles. “But here’s where it gets tricky — every child showed a different disturbance in a different gene.”

While some of the gene changes were inherited, others were not, suggesting that the variations could begin in the formation of the sperm and egg, much like the occurrence of Down syndrome. What’s more, some of the gene changes uncovered were previously associated with intellectual disability, meaning that there could be shared genetic risk factors for multiple developmental disabilities.

The variants identified occur in less than 1 percent of the general population, researchers said.