Autism is not one condition with a single cause but a spectrum of distinct biological and developmental profiles, according to scientists who analysed data from more than 45,000 autistic people across Europe and the US.
The study, published in Nature, found clear differences between those diagnosed in early childhood and those diagnosed later in life. Children diagnosed before the age of six typically showed early social and communication difficulties, often linked to a stronger genetic predisposition associated specifically with autism. These difficulties tended to remain stable over time.
By contrast, those diagnosed after the age of 10 often saw challenges emerge or worsen during adolescence. Their genetic profiles overlapped more closely with ADHD and mental health conditions such as depression and PTSD than with early-diagnosed autism. This group was more likely to face increasing behavioural and social difficulties, along with higher risks of co-occurring conditions.
“The term ‘autism’ likely describes multiple conditions,” said Dr Varun Warrier of the University of Cambridge, who led the research. “For the first time, we have found that earlier and later diagnosed autism have different underlying biological and developmental profiles.”
While the team stressed they are not proposing two separate diagnostic categories, they emphasised that autism should be understood as a gradient, with individuals falling along a spectrum influenced by multiple genetic and developmental factors.
The findings come amid a dramatic rise in diagnoses worldwide – an 800% increase in the UK between 1998 and 2018 – largely driven by broader diagnostic criteria and greater awareness. Researchers say breaking autism into more precise subgroups could improve both scientific understanding and the tailoring of support.
Prof Uta Frith, emeritus professor of cognitive development at University College London, said the results underscored the need to refine how autism is viewed: “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.”
