New  CDC  data found that autism spectrum disorder (ASD) diagnoses continued "a long-running trend" of rising between 2018 and 2020 — an increase many experts say "is really fueled by us doing a much better job in identifying minority children with autism."

Study details and key findings

Since 2000, the  Autism and Developmental Disabilities Monitoring Network  (ADDM) has documented a "long-running trend" of steady increases in autism prevalence among children, the  New York Times  reports.

On Thursday, CDC reported that ASD diagnoses continued to rise between 2018 and 2020. According to the study, an estimated one in 36 8-year-old children were diagnosed with ASD in 2020, up from one in 44 in 2018. Overall, around 4% of boys and 1% of girls were identified with ASD in the analysis from CDC's  Morbidity and Mortality Weekly Report (MMWR).

CDC's findings come from data on 8-year-old and 4-year-old children in 11 communities within the ADDM network in Arizona, Arkansas, California, Georgia, Maryland, Minnesota, Missouri, New Jersey, Tennessee, Utah, and Wisconsin. The data are not representative of the entire United States, CDC said.

There was a sharp increase in ASD prevalence among Black (2.9%), Hispanic (3.2%), and Asian or Pacific Islander (3.3%) children. This marks the first time autism was significantly more prevalent among 8-year-olds in these groups than in white children (2.4%), who have typically been more likely to be diagnosed with ASD.

"This is the opposite of racial and ethnic differences observed in previous ADDM reports for 8-year-olds," CDC authors wrote. "These shifts may reflect improved screening, awareness, and access to services among historically underserved groups."

In the analysis, the researchers also compared the number of autism evaluations and identifications among 4-year-olds in 2020 to the equivalent numbers from four years earlier. In the six months preceding the pandemic, autism evaluations and identifications were higher among 4-year-olds than they were four years earlier.

After the  World Health Organization  declared COVID-19 a pandemic in March 2020, autism evaluations and detections decreased significantly, falling below pre-pandemic levels through the end of 2020.

In another MMWR analysis of 2020 ADDM data, researchers suggested that during the early months of the COVID-19 pandemic, 4-year-olds were less likely to have an evaluation or be diagnosed with ASD than 8-year-olds when they were the same age.

"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," said Karen Remley, director of CDC's  National Center on Birth Defects and Developmental Disabilities.

"The data in this report can help communities better understand how the pandemic impacted early identification of autism in young children and anticipate future needs as these children get older," Remley added.

Commentary

Experts noted that the increase in ASD prevalence does not necessarily mean that the condition has become more common among children, adding that it could stem from other factors, including 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?"

According to Andy Shih, chief science officer of  Autism Speaks, it typically takes longer for less advantaged children to receive a diagnosis for conditions that involve a complicated diagnostic process. However, the increase likely signals that more children of color are receiving an ASD diagnosis and getting the help they need, Shih added.

"This increase is really fueled by us doing a much better job in identifying minority children with autism," Shih said. 

However, Walter Zahorodny, an author on the paper, said he believes better identification is not the only factor involved. 

"No one really knows what's driving autism rates higher," said  Zahorodny, who also serves as director of the New Jersey Autism Study and is an associate professor at  Rutgers University.

For years, experts have attributed rising rates to a variety of factors, including improved awareness, reduced stigma, re-labeling of kids, aging parents, low-birth-weight babies, and C-section deliveries. While all of these factors may contribute, Zahorodny thinks something else in our modern environment is driving the increase. 

"This is a true increase," Zahorodny said. "It constitutes a major public health crisis."

Ultimately, Lord said CDC's findings are promising. "It means we're finding kids younger," she said. (Weintraub, USA Today, 3/24; George, MedPage Today, 3/23; Anthes, New York Times, 3/23)