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Increasing Incidence of Autism Spectrum Disorders Continues in Indiana

Contributed by Dr. Cathy Pratt, BCBA-D,
Director, Indiana Resource Center for Autism

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In 2009, the Centers for Disease Control issued a report based on a sample of 8 year olds, and concluded that the prevalence of autism had risen to 1 in 110 in American children.  By 2012, using a similar sample, it was announced that the incidence had climbed to 1 in 88. Based on these latest numbers, 1 in 54 boys and 1 in 252 girls are being diagnosed with an autism spectrum disorder.    Last year in a telephone survey of 100,000 families, the incidence was projected at 1 in 50.  

If the projected incidence rates are accurate, what does this mean for Indiana? Based on the estimated census data from 2012, Indiana is home to 6,537,334 citizens. At an estimated rate of 1 in 88, there are potentially 71,911 individuals with a diagnosis on the autism spectrum. At the projected incidence of 1 in 50, the incidence is 130,747.  Remember these numbers are projected and only estimate the real occurrence of autism spectrum disorders in Indiana. No database exists in Indiana of the actual numbers of people on the autism spectrum either statewide or by county.

Another example of the increase of those diagnosed with ASD is the child count data collected by the Indiana Department of Education, Department of Special Education. These data are collected from public school districts across Indiana. According to the December 1 child count data, the number of students identified in 2009 was 10,643.  During that year, the incidence rate was 1 in 101.  By December 2010, that number had increased to 11,514 and as of December 2011 that count was 12,226.  According to the child count data from December 2012, the number of children served under that diagnostic category was 13,020.   And now according to the child count data from December 2013, the number of children served under this diagnostic category is 13,675. This shows an increase of 655 students from the previous year.

The number of students enrolled in Indiana’s public schools during the 2013-2014 school year is approximately 1,039,410. Using that data and the incidence data from December 2013, approximately 13 in 1000 students in Indiana have a diagnosis of an autism spectrum disorder. While the number of students served has increased, this year’s identification rate remains at 1 in 77.  The child count data does not include children who are not on special education service plans, and are home schooled or educated in non-public schools.   All who have either an IEP or special education service plan are counted.

While there is a general belief and awareness that autism spectrum disorders are on the rise, it is unclear why. Some believe that more children are being identified because the medical community and other professionals have a better understanding of autism spectrum disorders, and because the definition of autism has been expanded to encompass more individuals. Others believe that the increase is real and are advocating for research to investigate the potential causes of autism. Whether we believe the growth is because of increases in ASD or the result of changes in diagnosis, or both, the reality is that more Indiana citizens are being served under the eligibility category of Autism Spectrum Disorders. The other reality is that many of these children come with complex issues and support needs.  The potential impact on our schools and other service delivery systems continues to be tremendous. The strain on families is very real and significant.  



Pratt, C. (2014). Increasing incidence of autism spectrum disorders continues in Indiana.





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