The Facts: Understanding the Rise in Autism Diagnoses

Autism is widely recognised as a highly heritable neurodevelopmental condition, with estimates suggesting that genetics contribute to 60–90% of cases.

In approximately 40% of diagnosed individuals, specific genetic mutations or variations can be identified. While environmental factors do play a role in autism risk, such as air pollution and complications during pregnancy, these appear to be relatively minor contributors in most cases.

Studies from multiple countries have shown that shifts in Autism diagnostic practices and educational classifications have played a major role in the rising numbers in Autism Spectrum Disorder

A significant portion of the increase in autism diagnoses over recent decades is attributed to changes in how autism is defined and identified. Diagnostic criteria have broadened considerably since the 1980s.

Early definitions focused narrowly on observable behaviours in young children. Over time, diagnostic manuals evolved to recognise a broader spectrum of social, communication, and sensory traits, and allowed for co-diagnosis with conditions like ADHD. This has enabled many more people—especially those previously overlooked due to masking or atypical presentations—to access a formal diagnosis.

Studies from multiple countries have shown that shifts in diagnostic practices and educational classifications have played a major role in the rising numbers. In some cases, children previously labelled with an intellectual disability were later reclassified as autistic under updated criteria, which further contributes to the statistical rise.

Other factors may also influence prevalence. Older parental age, premature birth, and increased survival rates of at-risk infants have all been linked to a slightly elevated likelihood of autism.

Environmental factors such as maternal infections or exposure to air pollution during pregnancy are also under investigation, though their effects appear to be small in comparison to genetic influence.

Nicole Ennis-Oaks, Managing Director, NeuroNexus Psychology and Autism Specialist Consultant, explains "Importantly, broader awareness, reduced stigma, and improved access to early assessment services have encouraged more families to seek an autism diagnosis, which carries tangible benefits in terms of access to supports and understanding."

As an Autism Specialist who has supported hundreds of autistic individuals on the Central Coast NSW, Nicole Ennis-Oaks emphasises despite persistent myths, large-scale studies have repeatedly found no link between vaccines and autism, and any previous claims of such a connection have been thoroughly discredited.

According to Neuronexus Psychology specialists the rise in autism prevalence is best explained by Improved awareness and understanding,

In summary, the rise in autism prevalence is best explained by:

• Improved awareness and understanding

• Broader, more inclusive diagnostic criteria

• Earlier and more frequent screening

• Changing societal and environmental trends

  
  

"Autism remains a complex condition with diverse causes and presentations. Ongoing research continues to refine our understanding, but current knowledge already provides a strong foundation for early identification, meaningful support, and lifelong navigation," said Nicole Ennis-Oaks.