But experts in autism research say autism diagnoses are indeed increasing for adults, too, refuting Kennedy’s claims.

The claim

Kennedy, who has long speculated that vaccines given during childhood cause autism, said it is “an absurdity” to suggest that autism diagnoses have increased because of expanded diagnostic criteria and improved access to resources for school-age children.

“If we were just noticing it more, we would notice it in older groups. We’re not,” Kennedy said. “We’re only noticing it in kids who were born around 1989 or after. The older generations are not seeing those increases.”

The health secretary went on to say “something happened in the mid 90s” that made autism more prevalent. He acknowledged the decades of research that point to various genes that, when combined, present as autistic symptoms but said an environmental exposure of some kind is responsible for the society-wide increase in cases, referring to the concept of epigenetics.

“It has to be an environmental exposure because genes don’t cause epidemics,” Kennedy said. “It can provide a vulnerability, but you need an environmental toxin.”

The Washington Examiner contacted HHS with a request for comment.

The reality

While childhood and adolescent autism spectrum disorder diagnoses have been growing at a much higher rate, diagnoses for adults born before the 1990s have also increased in recent years.

There are likely multiple reasons for the rise in autism cases and for the difference in the rate of increase for adults and children. 

Expanded diagnostic criteria, as well as resource gaps, including health insurance coverage and access to specialists, could explain in part the lower numbers of adults receiving autism diagnoses compared to children. 

Adult autism diagnoses, in fact, on the rise

Multiple recent scientific studies indicate that autism spectrum disorder diagnoses are on the rise for adults.

A large-scale study involving more than 9 million insurance claims records published last year in the journal JAMA Psychiatry found ASD diagnoses increased 425% for adults between 26 and 34 from 2011 to 2022. The researchers also found a 338% increase in ASD diagnoses for adults between the ages of 35 and 44.

Another study published in JAMA Psychiatry in 2023 examined Medicaid enrollee data and had similar results. Overall, autism prevalence increased from 4.2 per 1000 enrollees in 2011 to 9.5 per 1000 in 2019, but the largest rate of increase was observed in 25 to 34-year-olds, up 195% in less than a decade.

Brenda Dater, executive director of the Association for Autism and Neurodiversity, told the Washington Examiner via email that Kennedy’s claims that autism diagnoses are only found among children “is not supported by the available evidence.”

Dater’s nonprofit group specializes in providing support to autistic or neurodivergent teenagers and adults. She says the most recent autism prevalence studies “show that more adults are being identified.”

“The absence of a diagnosis in an older person is therefore not evidence that autism was absent,” Dater said.

Potential for overdiagnosis

Adam Omary, psychologist and biostatistician for the libertarian Cato Institute, told the Washington Examiner the likely explanation for the rise in autism cases is because of the expansion of diagnostic criteria in the Diagnostic and Statistical Manual of Medical Disorders, more commonly referred to as the DSM.

The DSM-IV in 1994 was the first edition to categorize autism as a spectrum, but it still had more structured subcategories based upon specific symptoms, including Asperger’s disorder and “childhood disintegrative disorder.”

In 2013, the Diagnostic and Statistical Manual of Mental Disorders’ Fifth Edition created the phrase “autism spectrum disorder,” which created a single umbrella term replacing the multiple subcategory diagnoses. To be diagnosed, a person must show persistent deficits in understanding relationships, nonverbal communication, and social back-and-forth communication as well as some restricted or repetitive behaviors.

“Diagnostic drift is the far more likely driver and the question we should always address before looking for environmental causes,” Omary said.

Omary and his colleague, Dr. Jeffry Singer, a health policy specialist at Cato, have argued that state financial arrangements give schools and Medicaid service providers the perverse incentive to take advantage of looser diagnostic criteria to label children as mildly autistic if they are just socially awkward.

Omary told the Washington Examiner the updated diagnostic criterion also makes school-aged children more likely to receive a diagnosis than adults whom are less likely to be screened.

“Most of the autism screening is done in childhood, and today’s children are the first being diagnosed under newer, looser guidelines,” Omary said.

Resource gap for adults versus children

School-age children are more likely than adults to have access to disability support resources, effectively meaning that children are more likely to be evaluated for autism using looser criteria than in generations past.

“Older adults did not have the diagnostic criteria, public awareness, school identification systems, or access to assessment that exist today,” Dater said. “Autism was also frequently missed in people without intellectual disability and in girls and women.”

Dater said there is a shortage of mental health clinicians trained to assess autism in adults, particularly those who have the ability to mask their neurodiversity. Long waitlists and high out-of-pocket costs also put official diagnoses out of reach for many adults.

Having an official autism diagnosis can be helpful and even empowering for adults who have struggled in work, school, and social settings for years without fully understanding why. 

Zoe Gross, a director at the Autistic Self Advocacy Network, told The Atlantic in July that a formal diagnosis can unlock access to accommodations at school and work and secure protections from discrimination. Gross, who was diagnosed at age 4, said knowing that she struggles because of a disability “is really empowering.”

Dater said many autistic adults are first diagnosed with anxiety, depression, ADHD, or other conditions, which may be accurate but incomplete.

“An autism diagnosis can help someone better understand lifelong experiences that previously did not make sense and identify supports that better fit their needs,” Dater said.