Autism rates have been rising around the world, with a sharp increase in prevalence in the last decade. Australia has been no exception.

Indeed, autism diagnoses have risen much faster in Australia than in any other country. In particular, autism diagnoses among children have grown much faster in Australia than in other countries with similar economies and health systems.

Autism diagnoses have risen much faster in Australia than in any other country.Credit: Artwork: Marija Ercegovac

Is this increase in autism diagnosis related to the National Disability Insurance Scheme? The evidence strongly suggests that the answer to that question is yes. We will return to that evidence.

Many things are happening in Australia and in the world that impact autism diagnoses. Diagnostic criteria are changing. Diagnostic substitution is taking place – people are being diagnosed with autism when they would have been diagnosed with something else in the past. There is increasing awareness of autism. There may be genetic and environmental factors which are increasing the prevalence of autism. And, finally, the availability of government support may incentivise people to seek autism diagnoses.

Earlier this year, Sir Roland Wilson Scholar Maathu Ranjan and I conducted research into this, using data from the Medicare Benefits Scheme, the NDIS and the universe of social services records in Australia. We looked at the impact of the NDIS by studying the impact of its staggered roll-out. The NDIS started to be rolled out between 2013 and 2016 and was then increasingly extended to cover the entire country by 2019.

By comparing regions that received the NDIS to those that had not yet received it, we can precisely quantify the increase in diagnoses caused by the NDIS, as opposed to the general trend of increasing diagnoses in........

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