Background: The United States Centers for Disease Control and Prevention estimates that 1 in 68 American children will receive a diagnosis of autism spectrum disorder, or ASD. The rate has increased significantly since autism first appeared in the Diagnostic and Statistical Manual of Mental Disorders in 1980.

What’s new: The January issue of JAMA Pediatrics featured a study examining autism prevalence in Denmark, where rates of ASD have also increased. Because of the country’s nationalized health system, the researchers were able to examine the records of all 677,915 Danish children born between 1980 and 1991, following up until 2011. They determined that two-thirds of the increase in ASD rates could be attributed to changes in the diagnostic criteria in 1994 and the inclusion of diagnoses from outpatient facilities in 1995.

Why it’s important: This is the first large-scale study to quantify the effect changes in reporting practices have on ASD rates. Future research could determine the cause of the increase not explained by changes in reporting practices, as well as the generalizability of these findings to other countries, such as the United States.

Diagnosis Overview

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