Prevalence of Autism Spectrum Disorder in 7-9-Year-Old Children in Denmark, Finland, France and Iceland: A Population-Based Registries Approach Within the ASDEU Project.

Researchers checked autism counts in 7- to 9-year-olds across four countries. They used each nation's health and school records instead of running new tests.

Denmark, Finland, France, and Iceland supplied the numbers. The team wanted to see if autism rates looked the same in all four places.

Autism prevalence ranged from about one in two hundred kids to about three in one hundred. That is a seven-fold gap between the lowest and highest country.

The authors say the gap is not real biology. It comes from who gets noticed, who gets tested, and how doctors label the results.

Agiovlasitis et al. (2025) found girls score lower on the ADOS-II. Fewer flagged girls could shrink the count in countries that lean on that tool.

Duvekot et al. (2017) showed girls need bigger behavior problems to earn a diagnosis. This hidden-girl effect helps explain why some registries look smaller.

Bitsika et al. (2019) added that sex differences move depending on ADOS-2 severity. Countries using different severity cut-offs will count different kids.

When you read a prevalence report, ask how the region finds and scores kids before you compare it to your caseload. If you assess girls or multilingual learners, use tools and cut scores that catch subtler profiles so your count is fair and early help reaches everyone who needs it.