Autism should not be regarded as a single condition with a unified cause, researchers say, after uncovering clear genetic and developmental differences between people diagnosed in early childhood and those diagnosed later in life.
An international team analysed genetic data from more than 45,000 autistic people across Europe and the US, alongside behavioural data from birth cohorts. They found that children diagnosed before the age of six typically displayed early, stable difficulties with social interaction and communication, and had distinct genetic profiles. By contrast, those diagnosed after the age of 10 were more likely to experience worsening social and behavioural challenges during adolescence and showed stronger genetic links with ADHD, depression and PTSD.
“The term ‘autism’ likely describes multiple conditions,” said Dr Varun Warrier of Cambridge University’s department of psychiatry, senior author of the study published in Nature. “For the first time, we have found that earlier and later diagnosed autism have different underlying biological and developmental profiles.”
While the researchers emphasise that they are not proposing separate diagnostic categories, they argue that autism should be seen as a spectrum of overlapping conditions with varied genetic and developmental roots.
The findings come amid a sharp rise in autism diagnoses — an almost 800% increase in the UK between 1998 and 2018 — driven by broader diagnostic criteria and greater awareness. Autism is characterised by challenges with social communication, sensory processing and restrictive behaviours, but the way these traits present varies greatly between individuals.
The study found that early-diagnosed individuals were more likely to show developmental delays, such as slower walking and difficulty interpreting gestures, while later-diagnosed individuals often faced escalating problems during adolescence and more severe challenges by late teenage years.
Prof Uta Frith, emeritus professor of cognitive development at University College London, welcomed the work: “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.”
