Different forms of autism may exist, not only different severities, genetic study shows

The genetic analysis reinforces the complexity of autism spectrum disorder, and that there isn’t a single cause of autism.

People who learn they have autism after age 6 — the current median age at diagnosis — are often described as having a “milder” form of autism than people diagnosed as toddlers.

A new study challenges that assumption.

A genetic analysis finds that people with autism spectrum disorder diagnosed in late childhood or adolescence actually have “a different form of autism,” not a less severe one, said Varun Warrier, senior author of a study published Wednesday in Nature.

The “genetic profile” of people with late-diagnosis autism actually looks more like depression, attention-deficit/hyperactivity disorder and post-traumatic stress disorder than early childhood autism, said Warrier, an autism researcher at the University of Cambridge.

The study illustrates that autism is not a single condition with one root cause, but rather an umbrella term for a cluster of conditions with similar — although not identical — features, said Geraldine Dawson, founding director of the Duke Center for Autism and Brain Development, who wasn’t involved in the new report.