In nearly half of cases, the younger brothers and sisters of kids with autism also show signs of atypical development, researchers say.

Some 17 percent of younger siblings develop autism and another 28 percent show other types of delays in development or behavior, according to findings published in the Journal of the American Academy of Child and Adolescent Psychiatry.

For the study, researchers looked at 294 siblings of children with autism and 116 siblings of typically developing kids. All of the brothers and sisters were assessed at 6, 12, 18, 24 and 36 months to measure their development.

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Delays in the younger siblings could be spotted in children as young as 12 months, the study found. Among the siblings who experienced delays but did not have autism, they most commonly exhibited social or communication difficulties like extreme shyness or delayed pointing.

Researchers said their findings highlight the need for babies born to families that already have a child with autism to be screened regularly for any developmental or behavioral issues.

“This research should give parents and clinicians hope that clinical symptoms of atypical development can be picked up earlier, so that we can, perhaps, reduce some of the difficulties that these families often face by intervening earlier,” said the study’s lead author, Sally Ozonoff of the University of California, Davis MIND Institute.