On Jul. 9, 2025, researchers at Princeton University and the Simons Foundation have identified four clinically and biologically distinct subtypes of autism, marking a transformative step in understanding the condition’s genetic underpinnings and potential for personalized care.

Analyzing data from over 5,000 children in SPARK, an autism cohort study funded by the Simons Foundation, the researchers used a computational model to group individuals based on their combinations of traits. The team used a “person-centered” approach that considered a broad range of over 230 traits in each individual, from social interactions to repetitive behaviors to developmental milestones, rather than searching for genetic links to single traits. 

This approach enabled the discovery of clinically relevant autism subtypes, which the researchers linked to distinct genetic profiles and developmental trajectories, offering new insights into the biology underlying autism. Their results were published in Nature Genetics.

The study defines four subtypes of autism — Social and Behavioral Challenges, Mixed ASD with Developmental Delay, Moderate Challenges, and Broadly Affected. Each subtype exhibits distinct developmental, medical, behavioral and psychiatric traits, and importantly, different patterns of genetic variation. 

The team also found that autism subtypes differ in the timing of genetic disruptions’ effects on brain development. Genes switch on and off at specific times, guiding different stages of development. While much of the genetic impact of autism was thought to occur before birth, in the Social and Behavioral Challenges subtype — which typically has substantial social and psychiatric challenges, no developmental delays, and a later diagnosis — mutations were found in genes that become active later in childhood. This suggests that, for these children, the biological mechanisms of autism may emerge after birth, aligning with their later clinical presentation.