In the largest ever investigation of autism and sibling recurrence, a study revealed an increased risk that an infant with an older autistic sibling will also develop the disorder.
The study, which will be published in Pediatrics next month, found that at 19 per cent, the risk of recurrence was higher than previously thought -- at between 3 and 10 per cent.
It's estimated that the likelihood for boys is even higher, at over 26 per cent, and over 32 percent for infants with more than one older autistic sibling. For reasons that are still unknown, autism affects more boys than girls (about 80 per cent of all autistic children are males).
A complex disorder that affects a child’s ability to think, communicate, interact socially and learn, autism spectrum disorders (ASD) affects about 1 in 110 children born in the US.
Though there has always been strong evidence that genetic factors play a critical role in the development of autism, it wasn't clear just how much of a role until now.
The implications of the study could lead to more genetic counselling for parents and for referral to early intervention for the infant siblings of children with autism.
“Parents often ask what their risk of having another child with ASD is and, until now, we were really not sure of the answer,” said Sally Ozonoff, the study’s lead author and a professor of psychiatry and behavioural sciences at the University of California, Davis.
The study, which included 664 subjects from the United States and Canada, followed the infants' development until 36 months, when they were tested for autism using the Autism Diagnostic Observation Schedule (ADOS), an autism diagnostic tool, and the Mullen Scales of Early Learning, which "measures nonverbal cognitive, language, and motor skills".
Autism Speaks Chief Science Officer, Geraldine Dawson, stressed the importance of primary care professionals monitoring children’s development closely. Siblings, in particular, need screening "so that they can be offered intervention as early as possible. Early intervention ensures the best possible outcomes.”
Given the high incidence of recurrence, would you consider having another child if you had an autistic son or daughter?