Toddler siblings of autistic children are more likely to
exhibit some of the same atypical social behaviors as their brothers and
sisters with autism, even when they don't go on to develop the disorder, new
The siblings in the study were less likely to seek emotional cues from
adults, or respond to those cues, than toddlers who did not have a brother or
sister with autism.
The findings bolster the evidence for a strong genetic component to autism
and show that siblings of children with the disorder are at high risk for some
of the same social functioning deficits as their brothers or sisters.
University of California, San Diego assistant professor of psychology Leslie
Carver, PhD, presented the findings at the 2007 International Meeting for
Autism Research in Seattle.
Studying at-Risk Siblings
The risk that the younger sibling of an autistic child will also develop
autism or a related disorder is estimated to be around 2% to 8%, compared to
the latest CDC estimate that 1 in 150 children may have autism or a related
In an effort to better understand this risk and to identify the earliest
behavioral and biomedical markers of autism and related disorders, leading
autism researchers and research organizations established the High Risk Baby
Siblings Research Consortium in 2003.
"Studying this population should help us identify at-risk children
earlier so that we can get them the help they need as early as possible,"
Alison Singer, of the advocacy group Autism Speaks, tells WebMD. "It may
also give us important clues about the early onset of autism."
In the newly reported sibling research, Carver and colleagues compared the
social referencing reactions of toddlers with and without autistic
Social referencing refers to regulating your own behavior in response to the
behavior of others. It is expected that toddlers tend to begin social
referencing toward the end of their first year of life.
But this reaction tends to be impaired in children with autism.
The study involved 18 18-month-old siblings of children with autism (deemed
high-risk) and 28 18-month-olds with no family history of the disorder (deemed
In the behavioral portion of the experiment, the children were presented
with three new toys; their caregivers were trained to react to the toys with
facial expressions and vocal signals that were positive, negative, or neutral.
The interactions between the toddlers and the caregivers were videotaped.
The high-risk toddlers were found to differ in almost every aspect of social
referencing from their lower-risk counterparts. While they looked to adults as
quickly to gauge their reactions, they did so about 30% less often. And they
were less likely to respond to the cues they got from the adults.
Andy Shih, PhD, who manages the Baby Sibling Research Consortium, says the
findings underscore the importance of closely monitoring the high-risk siblings
of children with autism.
Shih is chief science officer for Autism Speaks.
"Clearly it is not just the siblings [with autism] who are being
affected," he says. "In order to help support families dealing with
autism, greater attention needs to be focused on all the children."
Singer's oldest daughter Jodie, now age 10, is autistic, while Jodie's
7-year-old sister Lauren is not.
Singer says her youngest daughter was a late talker who required two and a
half years of speech therapy.
"I was, of course, frantic early on," she says. "I watched her
like a hawk for signs. Parents who have a child with autism know the red flags,
but all parents need to know the early warning signs of autism."
Autism spectrum disorders include autistic disorder, Asperger's syndrome,
and pervasive developmental disorder (including atypical autism). These
disorders involve impairmentwith social, communicative, and behavioral
By Salynn Boyles
Reviewed by Louise Chang
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