Autism risk high in siblings
19 August 2011
The risk of babies developing autism if they have an older brother or sister with the disorder is higher than previously thought, the largest prospective (forward-looking) study to date shows.
The multi-site research showed around 19 per cent of babies will develop an autism spectrum disorder, such as autistic disorder, Asperger syndrome or pervasive developmental disorder (PDD), if an older sibling has already been diagnosed with the condition.
Previously the figure had been estimated at between 3 per cent and 10 per cent.
And the risk to the baby of developing autism is even higher for those with more than one older sibling with autism, and for male babies.
Having more than one older sibling with autism gave a baby a 32 per cent risk of also developing an autism spectrum disorder, US researchers said in the journal Pediatrics (2011, online 15 Aug).
In addition, the research confirmed the male preponderance of the condition, with 26 per cent of boys affected compared with 9 per cent of girls.
The study has implications for genetic counselling for parents and for early referral of babies for intervention, the researchers said.
Parents would need to check closely whether developmental milestones are being met, they recommended.
A total of 664 infants at 12 sites across the US and Canada took part in the study. The average age at enrolment was 8 months, and two-thirds were recruited before 6 months of age.
The development of all infants was tracked until age 36 months, when they were tested for autism.
A total of 132 infants met the criteria for an autism spectrum disorder.
Last Reviewed: 19 August 2011
- 1. Ozonoff S, Young GS, Carter A, et al. Recurrence risk for autism spectrum disorders: a Baby Siblings Research Consortium study. Pediatrics 2011; Aug 15. [Epub ahead of print]. doi: 10.1542/peds.2010-2825. http://pediatrics.aappublications.org/content/early/2011/08/11/peds.2010-2825 (accessed Aug 2011).
