


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 Center.



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."








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.



"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.