We have all heard about genetic and environmental factors being linked to the reason behind an autism diagnosis. Researchers have been working hard to focus their attention on modifiable autism in the hopes that they can discover some ways to prevent its development in a rather simple manner. Genetics have indeed been found to play a major role in the development of autism spectrum disorders, but researchers are now under the belief that genetics play a much larger role than even previously thought. MIND Institute from the University of California Davis’s Sally Ozonoff, along with her colleagues have discovered that among families who already have a child with autism, their risk of having a sibling also develop autism is substantially higher than previously believed.
It is now believed that siblings of a child with autism are really at a 20 times higher risk of also developing autism. Even though studies have previously been conducted in regards to the risk of recurrence among siblings of a child with an autism spectrum disorder, those trials have had limitations because of biases associated with the patient selection process along with a failure to take into account the tendency that parents of an autistic child have to stop having anymore children as well as failing to account for over-reporting.
Dr. Ozonoff personally evaluated 664 newborns into families who already had at least one child with an autism spectrum disorder. Her evaluations took place in 12 different positions throughout North America. The participants in the study were involved in the Baby Siblings Research Consortium which has been supported by Autism Speaks, an advocacy organization. All infant participants were enrolled in the study earlier than 18 months of age and were not evaluated for symptoms of autism spectrum disorder before turning 3 years of age. Researchers made autism spectrum diagnoses by using the reputable Autism Diagnostic Observation Schedule in addition to receiving an official diagnosis from a professional health care provider.
A total of 132 infants (29 girls and 103 boys) were screened positive. Nearly 41% were diagnosed with an autism spectrum disorder while 59.1% had some persistent developmental disorder which cannot be specified but does not accurately enough fit the criteria for autism or Asperger’s syndrome.
The overall results of this study revealed that newborns of families who already had an autistic child had a recurrence rate of 18.7%, nearly 20 times the risk of the average child of developing an autism spectrum disorder. Previous study results have estimated the rate of recurrence at as little as 3% and as high as only 10%.
Other studies have already been successful in proving that boys rate of developing autism is 3 times that of girls. When an older sibling was already diagnosed with autism, the recurrence rate for a boy younger sibling was as high as 26.2%. Babies with more than one older sibling with autism are two times more likely to be diagnosed than those who only have one sibling with an autism spectrum disorder.
According to Dr. Ozonoff, it is even possible that THIS study is underestimating the recurrence rate for siblings of a child with autism since the diagnoses of the participants were made at such a young age that sometimes the diagnoses are not accurate or not yet able to be made.
According to the researchers, since the recurrence rates seem to be so high, it is essential that physicians monitor children with an autistic sibling very closely by screening them frequently at their wellness visits.
References:
Ozonoff, S. “Recurrence risk for autism spectrum disorders: a baby siblings research consortium study.” Pediatrics. 2011.
Reynolds, D. 2011. Autism among siblings is more prevalent than originally suspected.