State-Level Trends in the Prevalence of Autism Spectrum Disorder (ASD) from 2000 to 2012: A Reanalysis of Findings from the Autism and Developmental Disabilities Network.
R Christopher Sheldrick, Alice S Carter
PMID 29654453WHAT IT FOUND
ASD prevalence varied widely by state from 2000 to 2012.
State differences grew over time, with 2012 estimates ranging from 6.9 to 24.6 cases per 1000 8-year-olds. A national average can hide large state differences.
Key findings
01State-level ASD prevalence estimates ranged from 3.4 to 9.5 cases per 1000 in 2000 and from 6.9 to 24.6 cases per 1000 in 2012.
02Between 2010 and 2012, growth in ASD prevalence fell in all states except Wisconsin.
03In 2012, Alabama had lower estimated prevalence than any other state, and New Jersey had higher prevalence than any other state.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
This is a reanalysis of published state-level estimates, not a new study that examined children directly. Prevalence depends on medical and educational records noting ASD symptoms, and access to educational records varies across states, so some state differences may reflect documentation rather than true differences. Only states with at least four ADDM surveys were included, giving 12 states, so the results do not cover all states equally. Alabama was not in the 2000 ADDM study; its 2000 estimate was inferred from later data, and Alabama estimates were unavailable in 2012. The study did not test why states differed, so it cannot show whether the differences were caused by true prevalence, awareness, diagnostic practice, service availability, or environmental factors. Analysis was at the state level, which may obscure local clusters of ASD cases.
Declared interests
The authors declared no conflicts of interest.
The easy way to misread this
Do not conclude that one state has fewer children with ASD than another because autism is truly less common there. The study did not test causes of the differences, and estimates depend on whether ASD symptoms are noted in medical and educational records.