The prevalence of autism spectrum disorder in American children rose between 2018 and 2020, continuing a long-running trend, according to a study released by the Centers for Disease Control and Prevention on Thursday. In 2020, an estimated one in 36 8-year-olds had autism, up from one in 44 in 2018. The prevalence was roughly 4 percent in boys and 1 percent in girls.
The rise does not necessarily mean that autism has become more common among children, and it could stem from other factors, such as increased awareness and screening.
“I have a feeling that this is just more discovery,” said Catherine Lord, a professor of psychiatry at the University of California, Los Angeles medical school, who was not involved in the research. “The question is what’s happening next to these kids, and are they getting services?”
The rise was especially sharp among Black, Hispanic, and Asian or Pacific Islander children. For the first time, autism was significantly more prevalent among 8-year-olds in these groups than in white children, who have traditionally been more likely to receive autism diagnoses.
“These patterns might reflect improved screening, awareness and access to services among historically underserved groups,” the researchers wrote.
But why the prevalence in these children has surpassed that in white children is an open question that requires more investigation, Dr. Lord said.
An accompanying study, also published on Thursday, suggests that the pandemic may have disrupted or delayed the detection of autism in younger children.
For this analysis, the researchers compared the number of autism evaluations and identifications for children who were 4 years old in 2020 to the equivalent numbers from four years earlier. In the six months before the pandemic began, autism evaluations and identifications were higher among the 4-year-olds than they had been in young children four years prior.
That is good news, Dr. Lord said. “It means we’re finding kids younger.”
But after March 2020, when the World Health Organization declared Covid-19 a pandemic, autism evaluations and detections plummeted, remaining below prepandemic levels through the end of 2020, the researchers reported.
Parents may have been less likely to bring their children in for autism evaluations during the pandemic, Dr. Lord said. The closure of schools and the shift to remote learning may have also made it harder for educators to identify children who might have benefited from evaluations or services.
“Disruptions due to the pandemic in the timely evaluation of children, and delays in connecting children to the services and support they need, could have long-lasting effects,” Dr. Karen Remley, director of the C.D.C.’s National Center on Birth Defects and Developmental Disabilities, said in a statement.
Both studies are based on data from the Autism and Developmental Disabilities Monitoring Network, which has used health and education records to track autism in communities across the United States since 2000.
The network has documented an increase in autism prevalence since 2000, when approximately one in 150 8-year-olds were estimated to have autism.
The 2020 data come from sites in 11 states and are not necessarily representative of the nation as a whole. Data from other locations could help provide a more comprehensive picture, Dr. Lord said.