The prevalence of autism spectrum disorders (ASD) among adults in the United States is rising rapidly, according to a new study.

Eric Rubenstein and colleagues analyzed a random sample of Medicaid records from 2011 through 2019, identifying individuals 18 years of age or older with a diagnosis of autism. They report, “In this cohort study of 403,028 Medicaid enrollees with autism claims over nine years of claims data, autism prevalence increased from 4.2 per 1,000 enrollees in 2011 to 9.5 per 1,000 enrollees in 2019. The largest increase was observed in the 25- to 34-year age group and the smallest increase in the 55- to 64-year age group.” The percentage of Medicaid enrollees with ASD who also had intellectual disability (ID) dropped from 62 percent in 2011 to 46 percent in 2019, potentially indicating a greater awareness of autism in individuals without ID.

The researchers conclude, “These findings suggest that despite difficulties in identifying autism in adults, there is a considerable and growing population of autistic adults among Medicaid enrollees, which may have future implications for the Medicaid system and understanding the needs of the autistic population.”

This article originally appeared in Autism Research Review International, Vol. 37, No. 4, 2023

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