Autism is becoming more common in young adults

Thanks to increased awareness, screening and evolving definitions, four times as many children have been diagnosed with autism over the past twenty years. A new study suggests that diagnoses have increased faster among younger adults over the past decade.

Researchers found that the rate of autism spectrum disorder increased 175% among U.S. residents from 2.3 per 1,000 in 2011 to 6.3 per 1,000 in 2022. The study, published Wednesday in JAMA Network Open, found that during this period, the rate of diagnosis increased faster among adults in their 20s and 30s.

Researchers involved in the study decided to assess how many adults had been diagnosed with autism because previous research had focused primarily on school-age children, said Luke Grosvenor, the study’s lead author and a postdoctoral fellow at Kaiser Permanente’s Northern California research division.

“There has been a lack of research focusing on autistic adults,” Grosvenor said.

The highest rate of autism was in children aged 5 to 8 years – 30.3 diagnoses per 1,000 children in 2022. The second highest rate was in children aged 4 years and younger – 28.8 per 1,000 children.

Study tracks rising rates of autism in adults

The study found much lower rates of autism in younger adults than in children, but also found that autism is increasing at a faster rate among these adults. The study found that the rate of autism among adults aged 26 to 34 increased by more than 450% between 2011 and 2022.

Rosvenor said rising autism rates among these adults show that “we need to improve transition services for autistic people and their families” as they become adults.

Although children can access services such as speech therapy and other therapy at school, they often lose access to such care as they grow older. But the need isn’t going away, Grosvenor said.

“There is a service gap for autism,” Grosvenor said, adding that it is “vitally important” that adults with autism receive the care they need.

Experts not involved in the study said it provides valuable information about the incidence of autism in adults, a group that federal researchers do not routinely monitor as part of autism surveillance.

Dr. Alycia Halladay, chief scientific officer of the Autism Science Foundation, said the study’s data showed results similar to those reported for young children by the Centers for Disease Control and Prevention. But she said the study’s estimates for adults are “extremely important” and highlight the need to monitor autism patients over time. She said the study also shows the value of collecting information from medical records to get a more detailed picture of people with autism.

Halladay, however, said the study does not provide a more detailed look at how older adults with autism cope. She said she would like to see a study of adults with autism that took into account issues such as educational attainment and employment prospects.

Autism rates vary by race and gender

The JAMA Network study also found differences in autism rates by race, ethnicity and gender. Diagnosis rates were highest among children and adults, American Indians or Alaska Natives. The increase in autism rates was greater among black, Asian, Latino, Indian and Alaska Native children compared to white children.

Boys were still more likely to be diagnosed with autism than girls, but the report noted that autism diagnoses increased faster among girls than boys over the study period.

Halladay concluded that biological factors contribute to the higher rate of autism among boys.

“Boys’ and girls’ brains are just different and develop at different rates,” Halladay said. “Girls previously had better social skills, which is why some people assume they may be better at masking autism features than boys.”