The prevalence of autism spectrum disorder among U.S. children reached its highest level to date in 2022, continuing a multiyear trend of increasing diagnoses, according to data released by the CDC.
Across 16 surveillance sites in 14 states and Puerto Rico, autism spectrum disorder (ASD) prevalence among 8-year-olds was 32.2 per 1,000 children (1 in 31), up from 1 in 36 in 2020 and 1 in 44 in 2018, as reported in the Morbidity and Mortality Weekly Report.
Estimates varied by site, ranging from approximately 1 in 103 in a south Texas county to 1 in 21 in a suburban county near Philadelphia and 1 in 19 near San Diego, California.
Variations in prevalence over time and across regions likely reflect differences in screening practices, diagnostic criteria application, and service accessibility, the researchers noted.
“The true or actual rate of autism [in the United States] is more likely to be closer to what this report has identified in California or Pennsylvania,” said study co-author Walter Zahorodny, PhD, of Rutgers University. “California in particular has a longstanding and robust program for screening and early intervention.”
Zahorodny added, “There is limited research that provides a clear explanation for the increasing prevalence.”
ASD prevalence in the U.S. has risen steadily since 2000. Contributing factors remain under investigation, but growing evidence—including a recent large-scale study—has linked maternal diabetes with increased risk of neurodevelopmental disorders, including ASD.
Robert F. Kennedy Jr., current head of the U.S. Department of Health and Human Services, recently set a September deadline for the National Institutes of Health to determine a cause for the increase, despite longstanding scientific consensus rejecting a causal link between vaccines and ASD.
The CDC emphasized that the surveillance populations do not represent the entire U.S. population, and the study was not designed to assess etiology.
A combination of genetic and environmental factors affecting early brain development is the most likely explanation for ASD, according to Lang Chen, MD, of Santa Clara University, who was not involved in the CDC study.
“There is no scientific evidence supporting a link between vaccines and autism,” Chen noted.
Zahorodny also highlighted that vaccine uptake has declined as ASD diagnoses have continued to rise.
Consistent with previous years, ASD prevalence was higher among Asian/Pacific Islander, Black, and Hispanic children than among white children. Children from these racial and ethnic groups were also more likely to present with co-occurring intellectual disability.
ASD remains more common among boys than girls. The data also indicate earlier identification, with higher diagnosis rates by age 4 among children born in 2018 compared with those born in 2014.
Increased awareness and evolving diagnostic criteria have contributed to rising prevalence but do not fully account for the trend, experts concluded.