Impact of the New DSM-5 Criteria for ASD on the Number of Children Receiving Autism Specific Funding: An Analysis of Change in Incidence over Time

Background: Changes made to the autism diagnostic criteria over time reflect our changing understanding of these conditions, as informed by research and clinical practice.  The most recent iteration of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) was released in May 2013, amid much controversy. Foremost was the concern that a subgroup of individuals who previously met DSM-IV criteria for a Pervasive Developmental Disorder (PDD) may no longer meet the DSM-5 criteria for Autism Spectrum Disorder (ASD). This outcome could potentially have implications for ongoing service provision and funding eligibility.  While previous research has provided important insights into the potential impact of the DSM-5 on prevalence estimates and the sensitivity of the revised diagnostic criteria, no studies have yet examined the population-level impact of the DSM-5 on the number of children receiving diagnoses in the community, and accessing autism support services.

Objectives: This study aimed to examine: (1) change over time in the estimated annual incidence of children diagnosed with ASD and registered to receive autism specific funding, and (2) trends in the number of diagnoses across PDD diagnostic groups, prior to and following the introduction of the DSM-5.

Methods:  De-identified data for 32,199 children aged under 7 years who were registered with the Helping Children with Autism Package (HCWA) in Australia from January 2010 to June 2015 was utilised. Eligibility criteria for HCWA requires diagnoses to be consistent with the DSM-IV or DSM-5 and confirmed by a Paediatrician, Psychiatrist or a multidisciplinary team.  The annual incidence of children diagnosed with ASD and registered with HCWA was calculated by dividing the total number of children registered each year, by the estimated population of children the same age. 

Results: The estimated annual incidence of children diagnosed with ASD and registered to receive autism specific funding increased from 20 per 10,000 in 2010 to 34.2 per 10,000 in 2013. Following the introduction of the DSM-5 in 2013, the estimated annual incidence of ASD plateaued, with no significant difference in incidence evident from 2013 to 2015 (see Figure 1).  Final results will also include an Interrupted Time Series Analysis to determine if this reflects a significant deviation from the overall trend of increasing diagnoses over time. A significant reduction in the proportion of Asperger’s Disorder and PDD-Not Otherwise Specified was observed from 2013, in line with the removal of these subtypes from the DSM-5.

Conclusions: Diagnostic criteria comprise an important element of the service environment that influences clinical behaviour and ensuing diagnoses of ASD in the community.  The findings suggest that the more stringent DSM-5 criteria may curb the trend of increasing diagnoses over time. However, further monitoring is required to assess the ongoing influence of the changes on diagnostic practice. Implications regarding access and availability of funding and support services will be discussed.