CNN  — 

A new study from the US Centers for Disease Control and Prevention shows that the autism diagnosis rate has increased among US children, continuing a long-term trend that experts have largely attributed to better understanding of and screening for the condition.

About 1 in every 31 children was diagnosed with autism by age 8 in 2022, up from 1 in 36 in 2020, according to the CDC report that published Tuesday. Rates varied widely by gender, race and geographic area.

The US Department of Health and Human Services launched what it called a “massive testing and research effort” last week with a goal to identify “what has caused the autism epidemic” by September, but the new CDC report says that better diagnostic practices can help explain many of the recent findings.

Improvements in early identification of autism “have been apparent,” the authors of the CDC report wrote, and “differences in the prevalence of children identified with [autism spectrum disorder] across communities might be due to differences in availability of services for early detection and evaluation and diagnostic practices.”

Boys have consistently had higher rates of autism diagnosis than girls – in 2022, there was a 3.4-fold difference in rates among 8-year-olds, according to the new CDC report. While that ratio has started to narrow in recent years, the new report notes that it’s not simply because of improvements in identification in girls.

Autism diagnosis was also more common among Asian, Black and Hispanic children than it was among White children, a shift that was first identified in the most recent past report that captured trends for 8-year-olds in 2020. In recent years, diagnoses have also shifted to become less prevalent in wealthy neighborhoods than in socially disadvantaged neighborhoods.

The reversal of these patterns is “consistent with increased access to and provision of identification services among previously underserved groups,” CDC researchers said in the new report.

But disparities persist in identifying autism in children who also have an intellectual disability. More than half of Black children diagnosed with autism at age 8 also had an intellectual disability, compared with less than a third of White children, the new report found.

Experts say that the rise in autism rates reflects a positive trend.

“A lot has changed over the years, and this continued rise in prevalence reflects, in part, real progress: increased awareness, broader diagnostic criteria, and more consistent, standardized screening tools have all contributed to more children being identified earlier and more accurately – underscored the need for continued support and investment in the autism community,” Dr. Andy Shih, chief science officer for Autism Speaks, a nonprofit advocacy and research group, said in a statement. Shih and Autism Speaks were not involved in the new report.

Dr. Kristin Sohl, who chairs of the autism subcommittee of the American Academy of Pediatrics’ Council on Children with Disabilities, called the findings in the new report “encouraging.”

“When children are identified early, appropriate supports and services can be tailored to help them, and their families thrive,” she said in a statement. “Autistic children add value to our communities. Advocating for resources and funding to support autistic people across the lifespan is essential for a productive and healthy America.”

The new study is based on surveillance data from 16 areas that participate in the CDC’s Autism and Developmental Disabilities Monitoring Network. The data are not nationally representative and encompass a different set of sites than the last report with data from 2020, which only captured data from 11 sites. The CDC has also said that the Covid-19 pandemic led to “sustained lower levels” of evaluations and identification of autism across most of the surveillance network.

Prevalence has also been found to vary widely by location; In 2022, rates ranged from about 1 in every 19 children in California to 1 in every 103 children in Laredo, Texas.

“Research has not demonstrated that living in certain communities puts children at greater risk for developing (autism spectrum disorder),” CDC researchers wrote. Instead, the difference in prevalence is more likely due to differences in the services available and practices used for evaluation and detection.

In California, where autism rates have consistently been highest, a local initiative has trained hundreds of pediatricians to “screen and refer children for assessment as early as possible,” the new report notes. Insurance coverage can help improve early detection and diagnosis, the researchers say. In Pennsylvania, the site with the second highest autism prevalence, the state Medicaid policy covers children with disabilities regardless of their parents’ income.

CDC researchers say in the new report that there are additional limitations on tracking autism prevalence, including varying levels of data quality and completeness and differences in identifying intellectual disability in a child and clinically diagnosing it.

“While there are many factors driving these numbers, research shows that 60–90% of autism risk is rooted in genetics. Still, one thing is clear—this steady increase in prevalence calls for deeper, sustained investment in autism research, not only to understand its causes, but also to support the growing number of people diagnosed today,” Shih said in his statement. “We must ensure that policies and budgets evolve to reflect this new reality. That means expanding access to early intervention, strengthening educational and healthcare systems, and providing supports that span a lifetime. This data is not just a number—it’s a call to action.”

CNN’s Sarah Owermohle contributed to this report.