Autism Risk Higher for Siblings

Eileen Bailey Health Guide
  • As parents, when you have one child with autism or Asperger's syndrome, you want to know the risk of additional children being diagnosed as well. In the past, the risk was considered low - somewhere between 3 percent and 10 percent. But a recent study has shown that the risk of siblings being diagnosed with autism is actually much higher and the more children you have with autism, the higher the risk.

    The results of the study were published in the August 2011 issue of Pediatrics. The study followed 664 infants who had at least one sibling who had been diagnosed with autism until they were 3 years old. At that time the children were classified as not having autism or having autism. At the end of the study, 132 of the infants were diagnosed with autism, that is almost 20 percent, much higher than the original estimates of 3 to 10 percent.

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    For infants with at least two older siblings with autism, the rate of diagnosis was even higher - 32 percent. In this group there was a large disparity between boys and girls. Boys with more than one siblings with autism had a 26 percent chance of also being diagnosed and girls had only a 9 percent chance.

    For parents looking at this information, it is important to note that 80 percent of the children in the study did not develop autism and other risk factors should be considered. Autism is considered hereditary but it is also believed that environmental factors are also involved. For many families, the risk involved has nothing to do with deciding whether to have additional children, however, these families should be more aware of the early warning signs of autism and have younger siblings evaluated to make sure early intervention services are utilized. Early diagnosis is considered to be an important factor in helping a child develop critical skills; behavioral strategies and treatments have a better chance of working when started early in life.

    Some of the early warning signs of autism are:

    • Lack of smiling or happy expressions from 6 months on
    • Lack of babbling by 1 year old
    • No sharing of emotional expression (sounds, facial expressions, smiling) with caregivers
    • Not responding to name by 1 year old
    • Not pointing to objects by 14 months
    • No words by 16 months
    • Loss of speech at any age

    It is important to realize that children develop at different rates and although your baby may show one or more of the preceding signs, it is not a definitive indicator that your child has autism. However, it does mean that you should discuss your concerns with your child's pediatrician and request a referral to a developmental pediatrician familiar with diagnosing autism in young children.


    Recurrence Risk for Autism Spectrum Disorders: A Baby Siblings Research Consortium Study, 2011, August, Sally Ozonoff et al, Pediatrics,

Published On: August 19, 2011