Nearly 1 in 5 younger siblings of children with an autism spectrum disorder (ASD, sometimes known just as autism) will eventually develop their own autism spectrum disorder, according to a new study.
The new data from researchers at University of California-Davis MIND Institute and Autism Speaks found that 19 percent of younger siblings of children with ASD developed autism, a rate significantly higher than the general population.
If there were two children with autism in the family, the risk of the third sibling developing an autism spectrum disorder increased to more than 32 percent.
This is the largest known study of younger siblings of children who have autism, and included 664 infants from 12 U.S. and Canadian sites who were evaluated as early as 6 months of age and followed until age 36 months.
“It has been well established that siblings of children with ASD are at higher risk for developing the disorder, but our estimates of the recurrence rate had been based on much smaller samples,” explained Autism Speaks Director of Research for Environmental Sciences Alycia Halladay, Ph.D.
The study found that the risk of an ASD diagnosis for male infants who had an older sibling with ASD was almost three times greater than the risk for female infants (26 percent compared to 9 percent).
The study did not find any increase in risk associated with the gender of the older sibling, severity of the older sibling’s symptoms, or other parent characteristics such as parental age, socio-economic status or race/ethnicity.
“By pulling together data from many investigators who are studying infant siblings of children with autism, these results offer a more accurate estimate of the recurrence rate for autism in siblings,” says Autism Speaks Chief Science Officer Geraldine Dawson, Ph.D.
“Surprisingly, the rate is much higher than previous estimates. This points to the important need for closely monitoring and screening siblings so that they can be offered intervention as early as possible to ensure the best possible outcome.”
“These findings emphasize the importance of family history as an autism risk factor that requires attention by parents and clinicians in tracking these infants from an early age to determine if the younger sibling develops ASD or a development disorder.”
The High Risk Baby Siblings Research Consortium, now engaging 25 scientists at 21 institutions in the U.S., Canada, Israel and the UK, is a partnership between Autism Speaks and the National Institutes of Health, led by the National Institute of Child Health & Human Development.
The study, entitled “Recurrence Risk for Autism Spectrum Disorders: A Baby Siblings Research Consortium Study,” was published online today in the journal Pediatrics and will appear in the September issue.
Source: Autism Speaks