Study Pinpoints Autism Subtypes, Opening Door To More Personalized Care

There are at least four distinct subtypes of autism, a new study finds, helping to explain the various trajectories of individuals on the spectrum and offering a path toward more targeted treatments.

Researchers grouped over 5,000 children ages 4 to 18 with autism based on more than 230 traits like social interactions, repetitive behaviors and developmental milestones to arrive at the classifications. Then, they assessed the children’s genetic profiles to uncover patterns characteristic of the different groups.

“These findings are powerful because the classes represent different clinical presentations and outcomes, and critically we were able to connect them to distinct underlying biology,” said Aviya Litman of Princeton University, a co-lead author of the study published this month in the journal Nature Genetics.

More than a third of children with autism in the study were in what the researchers dubbed the “Social and Behavioral Challenges” group. These children display core autism traits like social difficulty and repetitive behaviors and often have co-occurring conditions like attention deficit hyperactivity disorder, but tend to reach developmental milestones on schedule.

The “Moderate Challenges” group, which included about 34% of kids studied, experience a similar trajectory, but with milder presentations and no co-occurring psychiatric conditions. A third group known as “Mixed ASD with Developmental Delay” accounted for the roughly 19% of kids studied who exhibited delayed walking, talking and other developmental milestones, but without signs of anxiety, depression or disruptive behaviors.

A final group described as “Broadly Affected” had more extreme and wide-ranging challenges including developmental delays, social and communication difficulties, repetitive behaviors and co-occurring psychiatric conditions. About 10% of kids with autism fell into this category.

The study found clear genetic patterns to explain the different presentations. The Broadly Affected group had the highest proportion of problematic de novo mutations, those that are not passed down from either parent, the findings show. By contrast, individuals in the Mixed ASD with Developmental Delay group were more likely to have rare inherited genetic variants.

Notably, in the Social and Behavioral Challenges group, researchers found mutations in genes that typically activate later in childhood, which could explain why children in this group are often diagnosed at older ages.

“This study shows us that autism isn’t a single condition with a single cause,” said Dr. Andy Shih, chief science officer at Autism Speaks. “It’s a spectrum made up of many different experiences, challenges and underlying biology. By understanding those differences, we can work toward better care that is matched to each person’s unique needs.”

While the study identified four autism subtypes, the researchers said there could be more and that unlocking this information may have significant implications for families.

“Understanding genetic causes for more individuals with autism could lead to more targeted developmental monitoring, precision treatment and tailored support and accommodations at school or work,” said Jennifer Foss-Feig, a coauthor of the study and a clinical psychologist at the Icahn School of Medicine at Mount Sinai who also serves as vice president and senior scientific officer at the Simons Foundation Autism Research Initiative. “It could tell families, when their children with autism are still young, something more about what symptoms they might — or might not — experience, what to look out for over the course of a lifespan, which treatments to pursue and how to plan for their future.”