autistic kids have 20% chance of younger autistic siblings.
photo credit: Anita Zvonar
As a parent of one child with autism, I have long suspected that the rate of autism in younger siblings of children on the autistic spectrum was higher than the published reports of between 1 in 10 and 1 in 30. The journal Pediatrics has released updated findings from the largest sibling study of its kind which supports my suspicions. Unsurprisingly, the results show that in families with a child on the spectrum, there was a 1 in 5 chance that a younger sibling would develop autism as well. The rate was higher when the younger sibling was male (1 in 4) and lower when the younger sibling was a female (1 in 9).