Autism Is Not a Single Condition and Has No Single Cause, Scientists Conclude

New research from the University of Cambridge suggests that autism should not be understood as a homogeneous condition with a single cause. Scientists found that people diagnosed in early childhood often have a different genetic profile than those diagnosed later in life, broadening the understanding of how the condition develops.

The study analyzed the behavior of autistic people during childhood and adolescence in the United Kingdom and Australia. It also evaluated genetic data of more than 45,000 patients with the condition from diverse cohorts in Europe and the United States.

By linking genetic information to age at diagnosis, the researchers observed that the profiles of those identified early with the condition differed from those who received confirmation at later stages. They found only a slight overlap between the two groups, indicating that the biological mechanisms associated with autism in childhood may be different from those linked to autism identified in adolescence or adulthood.

The analysis, published last week in the journal Nature, showed that children diagnosed before the age of six were more likely to have behavioral difficulties—such as problems with social interaction—from an early age. In contrast, those diagnosed after the age of 10 were more likely to experience social and behavioral difficulties during adolescence. They also had a greater predisposition to mental health conditions, such as depression.

The study adds that the average genetic profile of those diagnosed later was closer to that of ADHD and conditions such as post-traumatic stress disorder than to that of “classic” autism identified in early childhood.

The study concludes that the timing of diagnosis is not entirely random, but reflects underlying genetic differences that, in some cases, coincide with risk for other conditions.

“For the first time, we have found that earlier and later diagnosed autism have different underlying biological and developmental profiles,” said Varun Warrier, a researcher in the Department of Psychiatry at the University of Cambridge and lead author of the paper, in a press statement. “The term ‘autism’ likely describes multiple conditions.”