Autism prevalence in Australia: What we know so far

There have been no systematic studies on the prevalence of Autism in Australia. Accurate prevalence data allows for planning necessary services and supports, and also helps to build community understanding for Autistic Australians. We know that Autistic individuals make up approximately 30% of people accessing the National Disability Insurance Scheme (NDIS), however without accurate prevalence data, it is difficult to know what proportion of Autistic individuals are receiving funding.

In this blog post, we’ll delve into some of our research that aims to understand the prevalence of Autism in Australia. OTARC researchers have conducted four studies that have created a clearer picture of the situation and highlighted areas where more attention and support may be needed.

Prospective identification of Autism in infants, toddlers, and preschoolers

Two of OTARC’s studies used the Social Attention and Communication Surveillance (SACS) method to identify Autism prospectively in infants, toddlers, and preschoolers. The SACS method identifies a set of behaviours or ‘early markers’ characteristic of Autistic children as young as 12 months old.

Study 1: Victorian Autism prevalence 0.84% (2006-2008)

The 2010 SACS study prospectively identified infants and toddlers with a high likelihood of Autism within their first two years of life. We trained Maternal and Child Health nurses to recognise early signs of Autism. They monitored a large sample of 22,770 children from 12 to 24 months. The study successfully identified children with a high likelihood of Autism, with a high positive predictive value of 81%.

Barbaro, J., & Dissanayake, C. (2010). Prospective identification of autism spectrum disorders in infancy and toddlerhood using developmental surveillance: the social attention and communication study. Journal of developmental and behavioral pediatrics. https://doi.org/10.1097/DBP.0b013e3181df7f3c

Study 2: Victorian Autism prevalence 3.3% (2013-2018)

The 2022 SACS study aimed to evaluate how well the SACS-R and SACS-PR tools can identify children with a high likelihood of Autism aged 11 to 42 months. The study found that the SACS-R had high diagnostic accuracy in identifying Autism between 12 and 24 months of age, while the SACS-PR at 42 months improved sensitivity. This research suggests that these tools can be helpful in identifying Autism early on in community-based settings.

Barbaro, J., Sadka, N., Gilbert, M., Beattie, E., Li, X., Ridgway, L., Lawson, L. P., & Dissanayake, C. (2022). Diagnostic Accuracy of the Social Attention and Communication Surveillance-Revised With Preschool Tool for Early Autism Detection in Very Young Children. JAMA network open. https://doi.org/10.1001/jamanetworkopen.2021.46415

Study 3: National Autism prevalence 1.5%-2.5% (2010-2011)

This study used Longitudinal Study of Australian Children (LSAC) data relating to a diagnosis of Autism prevalence in two age groups: Children recruited at kindergarten (born between 1999–2000) and at birth (0–1 years). Both groups were assessed every 2 years. Parents reported diagnosis and age of diagnosis for 10,090 children. Secondary analysis found a prevalence of a parent-reported diagnosis of Autism before age 7 in Australia of 2.5% in the birth group and 1.5% in the kindergarten group.

Randall, M., Sciberras, E., Brignell, A., Ihsen, E., Efron, D., Dissanayake, C., & Williams, K. (2016). Autism spectrum disorder: Presentation and prevalence in a nationally representative Australian sample. The Australian and New Zealand journal of psychiatry. https://doi.org/10.1177/0004867415595287

A follow up study using the same data followed up at age 12 (birth group) and 16 (kindergarten group) found an Autism prevalence of 4.4% and 2.6% respectively. The higher prevalence in the kindergarten group suggests that improved identification methods may be contributing to the increased prevalence rates.

Study 4: National Autism prevalence 0.74% (2010-2012)

This study used Helping Children with Autism registration data (HCWA) collected between 2010-2012 to determine Autism prevalence in Australia. A total of 15,074 children under the age of 7 were included. The HCWA registration data (2010-2012) showed that prevalence varies dramatically across states and territories, ranging from 0.97% in Victoria to 0.46% in Western Australia (WA) and 0.34% in the Northern Territory (NT). The low percentages in WA and NT may indicate the need for more identification services in their relatively large rural and regional areas.

Bent, C. A., Dissanayake, C., & Barbaro, J. (2015). Mapping the diagnosis of autism spectrum disorders in children aged under 7 years in Australia, 2010-2012. The Medical Journal of Australia. https://doi.org/10.5694/mja14.00328

What does it mean?

The variation in prevalence estimates across studies highlights the likely lack of diagnostic services and expertise, particularly in rural, regional, and remote areas. There is a clear need for a more comprehensive epidemiological study into Autism prevalence in Australia to facilitate the support, services and community understanding Autistic Australians deserve.

Acknowledgments

We would like to acknowledge our research participants whose invaluable contributions have made our work possible. Their commitment and willingness to share their time, experiences, and perspectives have significantly advanced our understanding of Autism and the potential impact of our research.

This content was presented to the Education and Health Standing Committee of Western Australia in response to the inquiry into support for Autistic children and young people in schools in Western Australia in 2023. Read the complete submission here [1.5MB].