Autism diagnosed later in life could be different form: study

U.S. President Donald Trump speaks in the Roosevelt Room of the White House, Monday, Sept. 22, 2025, in Washington. (AP Photo/Mark Schiefelbein)

Paris, France -- People who are diagnosed with autism later in life could have a different form of the condition than those diagnosed during childhood, a large study said Wednesday.

The findings come as U.S. President Donald Trump and his Health Secretary Robert F. Kennedy Jr. have been spreading disinformation about autism, saying there is an “epidemic” of cases and claiming unfounded links to vaccines and paracetamol.

The new research said it provides “further support for the hypothesis that the umbrella term ‘autism’ describes multiple phenomena” that affect people differently.

The study by a large international team of researchers sought to answer an important question for understanding autism: is there a difference between cases that are diagnosed in early childhood and those diagnosed much later -- beyond the age of 10?

For a long time, autism was considered to be a condition diagnosed in young children.

However, as the way autism is diagnosed has been expanded in recent decades, the condition has increasingly been identified in older people.

There are two theories that could explain the difference between these two groups, the researchers said.

One is that all people with autism have a similar underlying genetic profile, but some are not diagnosed during their youth because their symptoms might be more mild or subtle -- and only become more noticeable later on.

The other explanation could be that autism diagnosed during childhood and later on are actually different forms of the condition.

The study published in the journal Nature supports the latter theory.

After comparing the genetic profiles of thousands of people with autism in Denmark and the United States, the researchers determined there were significant genetic differences between those diagnosed earlier or later.

“People diagnosed with autism later in life are genetically more similar to those with attention deficit hyperactivity disorder (ADHD),” Thomas Bourgeron, a study co-author and researcher at France’s Pasteur Institute, told AFP.

Those diagnosed later in life also appear to be more at risk of mental health conditions such as depression, the study said.

People with autism are “very different from one another”, Bourgeron emphasized, calling for each patient to receive care tailored to their particular needs.

Uta Frith, an emeritus professor of cognitive development at University College London not involved in the study, said she was hopeful that in the future even more subgroups within autism “will come to light, and each will find an appropriate diagnostic label”.

“If there is talk about an ‘autism epidemic’, a ‘cause of autism’ or a ‘treatment for autism’, the immediate question must be: which kind of autism?”

AFP