Children who are diagnosed with autism spectrum disorder (ASD) often have larger than normal heads due to a condition known as early brain overgrowth. Although there has been speculation that overgrowth is a risk marker for autism, new evidence indicates there is no such relationship.
Lonnie Zwaigenbaum, MD, co-director of the Autism Research Center at the University of Alberta, Canada, and colleagues sought to examined the relationship between autism and head circumference.
They looked at whether head growth in the first three years differed among children with autism from a high-risk (HR) sample, HR siblings not diagnosed with autism, and a low-risk (LR) control group. Data came from the international Baby Siblings Research Consortium.
There was no overall difference in head circumference growth during the first three years between HR and LR infants, the researchers reported in the Journal of the American Academy of Child & Adolescent Psychiatry.
However, secondary analyses suggested possible increased total growth in HR infants. Also, analyses stratifying the HR group by three-year outcomes did not detect differences in head growth or height between HR infants who developed autism and those who did not, nor between infants with autism and LR controls.
“Head growth was uninformative as an [autism] risk marker within this HR cohort,” the researchers concluded.
While early brain overgrowth is frequently reported in autism spectrum disorder (ASD), the relationship between ASD and head circumference (HC) is less clear, with inconsistent findings from longitudinal studies that include community controls.
Our aim was to examine whether head growth in the first three years differed between children with ASD from a high-risk (HR) sample of infant siblings of children with ASD (by definition, multiplex), HR siblings not diagnosed with ASD, and low-risk (LR) controls.