Changes in prevalence of autism spectrum disorders in 2001-2011: findings from the Stockholm youth cohort.

Idring et al. (2015) counted every child with an autism diagnosis in Stockholm from 2001 to 2011. They used medical and school records to track how many kids got the label each year.

The team split the kids into two groups: those who also had intellectual disability and those who did not.

Diagnosed autism nearly quadrupled, rising from about 4 in every 1,000 children to about 18 in every 1,000. Almost all of that jump came from kids without intellectual disability.

The increase was steady year after year, not a sudden spike.

Nygren et al. (2012) saw the same four-fold jump when they screened every 2-year-old in Gothenburg. Both Swedish studies point to better detection, not more cases.

Hewitt et al. (2016) extended the Stockholm picture by race. In Minneapolis, Somali and White children were identified at the same rate, but Somali kids with autism were more likely to also have intellectual disability.

Safer-Lichtenstein et al. (2021) showed that in the U.S., state politics and wealth drive school-identified rates. Their finding supports Stockholm’s view: where and how you look for autism changes the count more than true prevalence does.

When numbers climb this fast, families and funders worry about an epidemic. This study says the rise is mostly catching kids we used to miss, especially those without intellectual disability. For BCBAs, it means caseloads will keep growing, but the new clients may need subtler, language-rich interventions rather than intensive daily living skills. Use the Stockholm pattern to explain to parents why their child is one of many newly identified — and why early ABA still matters.