Accelerated Early Growth Linked to Autism

According to a recent study, increased early growth in male toddlers may be connected to autism spectrum disorders (ASDs).

The researchers reported that of the young autistic males studied, those in the top 10% of overall physical size during infancy displayed more severe social deficits and lower adaptive functioning by toddlerhood.

Numerous previous studies have attempted to evaluate the potential relationship between head circumference overgrowth during the first year of life and autism, but "it is unclear whether this phenomenon is independent of overall body growth," the authors stated.

"We replicated what has been found before about head overgrowth, which seemed to occur between 6 and 12 months in the kids with autism," said principal investigator Katarzyna Chawarska, PhD, associate professor of child psychiatry at the Child Study Center at Yale University School of Medicinein New Haven, Connecticut.

"However, we also found that head overgrowth was associated very strongly with overgrowth in terms of skeletal development. So we can conclude that it is part of a more generalized phenomenon," she continued.

The retrospective study assessed data on 129 boys who were enrolled in early cognition studies at the Yale Toddler Developmental Disabilities Clinic prior to their third birthday.

In this group of young boys, 64 were on the autism spectrum, 34 had a non-specific, all-encompassing developmental disorder, 13 suffered from global developmental delay, and 18 had various other developmental problems.

The researchers also examined data on 55 boys in a healthy control group who were determined to be developing at a normal rate.

They found that the boys on the autism spectrum were notably longer by the age of 4.8 months, and by the age of 11.4 months, they weighed much more than the healthy control participants.

These autistic toddlers also had a head circumference that was much larger by the age of 9.5 months. At 12 and 18 months, this difference was still noticeable in comparison to the control group, but by the age of 25 months, the difference was no longer considered significant.

Further, the researchers found that boys in the autism group who were in the top 10% of overall physical size during their first year displayed more severe of social deficits and lower adaptive social functioning at the age of two in comparison to other autistic boys with a less extreme growth pattern.

"These results illustrate the complexity of early growth patterns in disabled populations and highlight that accelerated growth along all three dimensions seems to occur only in those with severe social disabilities due to autism," wrote the researchers.

"I think this study raises a number of questions about overgrowth and its relationship with autism, and it highlights the importance of studying factors that influence not only neuronal development but also skeletal growth," said Chawarska.

Chawarska was careful, however, to note that overgrowth in an infant is not a diagnostic marker for autism.

"Having a child who is growing rapidly does not by itself mean the child is autistic,” she said. “And it doesn't mean that all children with autism will show this particular pattern of growth.”

“Nonetheless,” she added, “presence of atypical overgrowth is always reason for further investigation."

The researchers noted that that future studies should focus on potential effects overgrowth may have on autistic children into adolescence, and whether these results affect autistic females.

The study was published in the October issue of the Archives of General Psychiatry.