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According to experts who analyzed biological data from over 45,000 people with autism across Europe and the US, the condition must not be regarded as a single condition with one underlying origin.

The global study showed that individuals identified with autism at a young age, usually prior to six years old, often have a different genetic profile than those diagnosed at an older age.

Key Findings from the Study

• Early-diagnosed individuals were more likely to exhibit social challenges from a young age, such as problems with social interaction, but stay consistent over time.
• Those identified with autism later, typically past ten years old, tended to experience growing social and behavioral challenges in adolescence and additionally showed an increased likelihood of mental health conditions such as anxiety.

"The label ‘autism’ probably refers to multiple disorders," explained the lead researcher, senior author of the research. "Initially, we have found that early and later diagnosed autism have different underlying and developmental characteristics."

No Two Categories, But a Spectrum

These experts do not recommending a shift towards dual diagnostic groups, saying that this could be counterproductive for the many that are in between.

"It is a spectrum," Warrier commented. "There are also numerous other elements that contribute to when someone is diagnosed, so the moment you move from averages to something that is relevant to an individual, it's false equivalency."

Increasing Autism Identification Rates

These results come at a time when autism identification has increased steeply, with a almost 800% increase in diagnoses in the UK between 1998 and 2018.

Specialists say this is mainly because of a broadening of the diagnostic criteria and increased recognition of the disorder.

Diversity and Subgroups in Autism

Furthermore, while autism is characterized by experiencing difficulties with social communication, sensory processing, and repetitive behaviors, there is significant variability in how these difficulties present between people.

Scientists have been investigating whether the group clusters into categories, with common traits or paths, that could make researching autism more manageable.

Study Approach and Genetic Insights

The recent research used behavioral data from several study groups and biological information from multiple extensive studies, with over 45,000 individuals.

Previously, it was commonly thought that those identified sooner were usually those with more pronounced autistic features, underpinned by people having a greater amount of autism-linked gene variants.

However, the latest study revealed a different trend.

Different Genetic Patterns and Developmental Paths

The analysis found that the biological genetic profiles differed between those diagnosed with autism sooner and later in life, with only a modest similarity.

The average genetic profile of later-diagnosed autism is more similar to that of ADHD, as well as to mental health disorders such as depression and PTSD, than it is to autism diagnosed in young children.

• Those diagnosed before the age of six years tended to be slow to walk and have difficulty understanding hand gestures and often experience social and communication challenges that appeared soon but stayed consistent.
• Those identified past the age of 10 years tended to experience an rise in challenges during teen years and, by late adolescence, displayed more significant difficulties.

"This gives me hope that even more categories will be identified, and every one will receive an appropriate diagnostic label," stated an expert in cognitive development, who was not involved in the study. "It is time to realize that ‘autism’ has become a ragbag of various conditions."