Autism should not be seen as a single condition with one underlying cause, according to scientists who found that people diagnosed in early childhood often have a different genetic profile to those diagnosed later in life.
The research, based on genetic data from more than 45,000 autistic people across Europe and the US, revealed that children diagnosed before the age of six typically showed early behavioural and social communication difficulties that remained stable over time. By contrast, those diagnosed after the age of 10 were more likely to experience worsening difficulties during adolescence and faced a higher likelihood of co-occurring conditions such as depression.
“The term ‘autism’ likely describes multiple conditions,” said Dr Varun Warrier of Cambridge University’s department of psychiatry, the study’s senior author. “For the first time, we have found that earlier and later diagnosed autism have different underlying biological and developmental profiles.”
Published in Nature, the study challenges the traditional view that earlier-diagnosed autism simply reflects more pronounced autistic traits. Instead, the analysis showed that the genetic profiles of early- and later-diagnosed autism differ significantly, with only modest overlap. Later-diagnosed autism was found to be genetically closer to ADHD and mental health conditions such as depression and PTSD.
Children diagnosed early were more likely to be slow to walk, struggle with hand gesture interpretation, and show early-emerging social and communication issues that persisted but did not dramatically worsen. Those diagnosed later tended to develop increasing challenges through adolescence, which by late teenage years became more severe.
While the researchers emphasised they are not calling for two separate diagnostic categories, they highlighted the importance of recognising autism as a spectrum with diverse biological pathways.
Prof Uta Frith, emeritus professor of cognitive development at University College London, 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.”
The work comes amid an 800% rise in autism diagnoses in the UK between 1998 and 2018, largely attributed to broader diagnostic criteria and greater awareness. Experts believe that better understanding autism subtypes could transform approaches to diagnosis, support, and treatment.
