Autism may represent multiple conditions rather than a single disorder with one cause, according to new research that identified distinct genetic and developmental profiles depending on the age of diagnosis.
An international study of more than 45,000 autistic people across Europe and the US found that children diagnosed before the age of six typically had a different genetic makeup compared with those diagnosed after the age of 10.
Early-diagnosed children were more likely to display social and communication difficulties from a young age, often remaining stable over time. Later-diagnosed individuals, however, tended to develop increasing social and behavioural difficulties during adolescence and had a higher likelihood of mental health issues such as depression.
“The term ‘autism’ likely describes multiple conditions,” said Dr Varun Warrier, senior author of the study from the University of Cambridge’s department of psychiatry. “For the first time, we have found that earlier and later diagnosed autism have different underlying biological and developmental profiles.”
Despite the differences, the researchers cautioned against splitting autism into two categories, stressing that many people fall somewhere in between. “It is a gradient,” Warrier explained.
The findings, published in Nature, come amid a sharp rise in autism diagnoses – almost 800% in the UK between 1998 and 2018 – attributed largely to broader diagnostic criteria and greater awareness.
The study showed that the genetic profile of later-diagnosed autism overlaps more closely with ADHD and mental health conditions such as depression and PTSD, while early-diagnosed cases are more strongly linked to autism-specific genetic variants.
Children diagnosed earlier were more likely to be slow walkers, struggle with interpreting gestures, and show stable difficulties in social communication. Those diagnosed later typically saw their challenges intensify during adolescence and present more severely by late teenage years.
Prof Uta Frith, emeritus professor of cognitive development at UCL, who was not involved in the study, welcomed the findings. “It makes me hopeful that even more subgroups will come to light, and each will find an appropriate diagnostic label. It is time to realise that ‘autism’ has become a ragbag of different conditions,” she said.
