Boys With Autism May Grow Faster as Babies10/07/11
FRIDAY, Oct. 7 (HealthDay News) -- Boys with autism tend to grow
faster as babies, with differences from typically developing
infants seen in their head size, height and weight, a new study
Researchers said the findings may offer new clues about the
underlying mechanisms of autism. A larger head size probably means
the children also have a larger brain.
Boys with brain and body "overgrowth" tend to have more severe
autism symptoms, particularly involving social skills, than
autistic children who don't grow faster than normal. So, it's also
possible the overgrowth is one of the causes of autism; that it
somehow makes symptoms worse or represents a subtype of autism
that's marked by both accelerated growth and severe social
deficits, said study author Katarzyna Chawarska, an associate
professor of child psychology at the Yale University Child Study
Prior research has also found an association between accelerated
head growth and autism. This study adds to that by showing that
boys with autism have a tendency toward accelerated growth
throughout the rest of the body.
"We found these children tend to have accelerated growth patterns in skeletal growth, including length or height, and a little later we see them getting a little heavier, suggesting enhanced muscle growth," Chawarska said.
While the focus of research has been on understanding why the
brain grows faster in autistic kids, "now we need to extend our
search to other factors that affect multiple morphological
[structural] features," she said. "We need to ask why growth
factors may be dysregulated in autism. And that's something we have
no answer to now."
The study is published in the October issue of the
Archives of General Psychiatry.
Autism is a neurodevelopment disorder that's characterized by
problems with social interaction, verbal and nonverbal
communication and restricted interests and behaviors. An estimated
one in 110 U.S. children has the disorder, according to the U.S.
Centers for Disease Control and Prevention.
In the study, researchers analyzed pediatricians' medical
records on 64 children with autism; 34 boys with pervasive
developmental disorder-not otherwise specified (considered an
autism spectrum disorder); 13 boys with global development delay,
18 boys with other development problems and 55 typically developing
Though they were of normal size at birth, compared to typically
developing kids, boys with autism were longer at about 5 months
old, had a larger head circumference at 9.5 months and weighed more
by their first birthday.
The growth of the head was not out of proportion to the rest of
the body; instead, the whole child grew bigger than normal,
according to the study.
None of the children with other types of developmental problems
showed similar growth patterns.
Boys who were in the top 10 percent for overall physical size in
infancy had more severe social deficits and were lower functioning,
according to the study.
Still, researchers stressed that "overgrowth" should not be used
to diagnose autism, since not all kids who are later diagnosed with
autism grow more rapidly than normal, and a large head
circumference can indicate conditions other than autism.
However, pediatricians should play close attention to kids with
an accelerated growth pattern, and perhaps refer them for genetic
testing, Chawarska said.
Chawarska and her colleagues plan on conducting a similar study
in girls, and investigating the possibility that interfering with
overgrowth might help ease autism symptoms.
"That is highly speculative, and at this point we don't have a good model explaining how this might work," she noted.
Geraldine Dawson, chief science officer for Autism Speaks, an
advocacy organization, said the study suggests interesting new
areas of research, including the role that "neuroinflammatory
processes" may play in excessive head growth.
"These findings indicate that autism is not a static condition. Rather, there are dynamic changes in the brain during early postnatal life," Dawson said. She noted that the abnormal head growth typically happens around the time that autism symptoms begin to appear.
"Therefore, there may be a direct connection between the abnormal neural processes that are accounting for abnormal head growth and the emergence of autism symptoms," Dawson said, although what is causing the brain enlargement remains unclear.
National Institutes of Health has more on autism.
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