Researchers from the University of California, Davis, have identified a subtype of autism associated with enlarged brain volume, marking a key advancement in understanding this complex neurodevelopmental disorder.
A groundbreaking study from the MIND Institute at UC Davis, published in Biological Psychiatry on November 2, 2020, draws on two independent investigations. One examined brain size in autistic children, while the other analyzed white matter development—the neural pathways that facilitate information flow. By reviewing serial medical imaging, the team monitored brain changes longitudinally.
To conduct this research, experts analyzed over 1,000 MRI scans from 294 children with autism aged 3 to 12, alongside 135 typically developing children. Their findings revealed that certain autistic children exhibit significantly larger brains, a condition termed disproportionate megalencephaly, which correlates with greater intellectual disability.
Earlier research from 2009 noted enlarged brains in young autistic children, but assumed normalization with age. This study challenges that, showing that brains larger than average at age 3 remain so by age 12. Notably, autistic children with intellectual disabilities most often have these oversized brains, elevating the risk of lower IQ.
“Larger brain size in autism has been associated with lower IQ, and children with intellectual disabilities are harder to scan as they get older,” explains David Amaral, PhD, co-author and distinguished professor at UC Davis.
The study also highlights that white matter development varies by autism subtype and severity. Children with more severe autism show delayed white matter maturation. These insights, grounded in rigorous longitudinal data, pave the way for targeted interventions and improved care for autistic children.
