The percentage of American children estimated to have autism spectrum disorder increased in 2022, continuing a long-running trend, according to data released on Tuesday by the Centers for Disease Control and Prevention.

Among 8-year-olds, one in 31 were found to have autism in 2022, compared with 1 in 36 in 2020. That rate is nearly five times as high as the figure in 2000, when the agency first began collecting data.

The health agency noted that the increase was most likely being driven by better awareness and screening, not necessarily because autism itself was becoming more common.

That diverged sharply from the rhetoric of the nation’s health secretary, Robert F. Kennedy Jr., who on Tuesday said, “The autism epidemic is running rampant.”

Mr. Kennedy has repeatedly tried to connect rising autism rates with vaccines, despite dozens of studies over decades that failed to establish such a link. The health secretary nonetheless has initiated a federal study that will revisit the possibility and has hired a well-known vaccine skeptic to oversee the effort.

Mr. Kennedy recently announced an effort by the Department of Health and Human Services to pinpoint the “origins of the epidemic” by September, an initiative that was greeted with skepticism by many autism experts.

“It seems very unlikely that it is an epidemic, in the way that people define epidemics,” said Catherine Lord, a psychologist and autism researcher at the David Geffen School of Medicine at the University of California, Los Angeles.

A significant part of the increase instead can be attributed to the expansion of the diagnosis over the years to capture milder cases, Dr. Lord said, as well as decreased stigma and greater awareness of support services.

Still, she left open the possibility that other factors are contributing to more children developing autism. “We can account for a lot of the increase but perhaps not all of it,” Dr. Lord said.

“But whatever it is, it’s not vaccines,” she added.

Autism is a neurodevelopmental disorder characterized by difficulties with social interactions and communication, sensory issues and repetitive interests and behaviors.

While the causes remain largely unknown, researchers believe it has a strong genetic component. “It’s very unlikely that it’s one cause or even a small number of causes,” Dr. Lord said.

The new data were collected by the C.D.C.’s Autism and Developmental Disabilities Monitoring Network, which used the health and education records of more than 274,000 children at 16 sites across the country to estimate autism rates.

The prevalence of the disorder has risen steadily since the year 2000, when the network first began tracking it.

Other trends were evident in the new research. While white children and children from wealthier socioeconomic areas long had the highest rates of autism in the United States, that trend flipped in 2018.

Starting in 2020, greater percentages of Black and Latino children were found to have autism, and the association with wealthier communities was no longer seen in the data.

The C.D.C. reported prevalence rates of 3.7 percent among Black children, 3.3 percent among Hispanic children and 3.8 percent among Asian American children, compared with 2.8 percent among white children.

While autism has long been associated with boys, a difference that may be tied to genetics, girls are now diagnosed at higher rates as awareness has grown about the subtler ways the disorder can manifest, often emerging more clearly in teenage years.

Autism was 3.4 times more prevalent in boys than girls in 2022, down from 3.8 times higher in 2020, the C.D.C. said.

The data also showed surprising variability in autism diagnoses by geography, ranging from 5.3 percent of 8-year-olds in California to just under 1 percent in Texas.

The availability of certain medical and educational resources increases the likelihood that these children will be identified. California, for example, has a program that trains local pediatricians to identify signs of autism at an early age, as well as regional centers that provide autism services.

Pennsylvania, which had the second-highest prevalence, has a state Medicaid program that guarantees coverage for children with developmental disabilities regardless of their parents’ income.