Autism Severity Linked to Prenatal Brain Overgrowth in New Study

A new study from the University of California San Diego has uncovered a key biological basis for the varying severity of autism spectrum disorder (ASD). By creating brain cortical organoids (BCOs) from the stem cells of toddlers with and without autism, the team discovered a striking correlation between autism severity and excessive prenatal brain growth.

The study, published in Molecular Autism, found that BCOs derived from toddlers with severe autism were up to 40% larger than those from neurotypical controls. "The bigger the brain, the better isn't necessarily true. In the brain organoids from toddlers with profound autism, there are more cells and sometimes more neurons—and that's not always for the best," explained Alysson Muotri, senior author of the study.

Crucially, the rate of accelerated growth correlated with symptom severity. "The larger a toddler's BCO size, the more severe their social and language symptoms were later in life," the researchers noted. Toddlers with the most enlarged BCOs exhibited excessive brain volume in areas governing social skills, language, and sensory processing.

Co-lead researcher Dr. Eric Courchesne called the findings "one of a kind," highlighting their potential for early autism detection and intervention. "We need to understand the underlying neurobiological causes of those challenges and when they begin. We are the first to design an autism stem cell study of this specific and central question."

The study lends support to the theory that autism originates prenatally through dysregulated neurodevelopmental processes. As Courchesne stated, "It's long been assumed that autism begins prenatally and involves multiple stages and processes." By pinpointing excessive prenatal brain growth as a key factor, the researchers have taken a major step toward explaining the condition's heterogeneity.

Looking ahead, Courchesne and Muotri aim to identify the underlying drivers of prenatal overgrowth, paving the way for potential therapies. As Muotri noted, "Now that we have established that brain overgrowth begins in the womb, we hope to pinpoint its cause, in a bid to develop a therapy that might ease intellectual and social functioning for those with the condition."