The largest group—consisting of 1,976 people—shows mild challenges in core autism traits, whereas the smallest—554 people—has severe difficulties across those same traits. The other two subtypes are somewhere in between: One group specifically experiences social challenges and disruptive behavior, and the other shows developmental delay and difficulties in select traits.

People belonging to the same subtype often share the same co-occurring diagnoses, further analysis found. Those with social difficulties and disruptive behavior, for instance, are more likely than the other groups to have a diagnosis of attention-deficit/hyperactivity disorder or anxiety, and those in the strongly affected group are more likely to show cognitive impairment.