Five Explanations for Rising Autism Rates That Aren’t Vaccines or Tylenol

By Ross Pomeroy  |  October 16, 2025 | 10:42am
Photo by The White House
Healthcare Autism
Five Explanations for Rising Autism Rates That Aren’t Vaccines or Tylenol

It’s hard to teach an old dog new tricks, but it’s even harder to convince a 71-year-old Secretary of Health and Human Services that vaccines and Tylenol don’t cause autism. 

Robert F. Kennedy, Jr. has called the large increase in autism diagnoses over the past few decades an “epidemic” caused by “an environmental toxin.” Through his actions at HHS, specifically, restricting the availability of and denigrating vaccines and advising pregnant women to avoid taking acetaminophen (the drug in Tylenol), he’s made clear what he thinks the “toxins” are. 

Scientists who have researched autism extensively counter pretty much all of RFK Jr.’s assertions. Autism Spectrum Disorder, which is characterized by problems with social interaction and restricted or repetitive behaviors or interests, is almost entirely genetic, with limited contributions from environmental factors. A large study published in 2019 estimated autism’s heritability at about 80 percent – equivalent to the heritability of height. 

In various studies, conducted over decades, scientists have thoroughly debunked the notion that vaccines in any way cause autism. The research on acetaminophen’s potential link to autism is less well-developed, but as of now, there is no convincing data tying pregnant women’s use of the drug to greater risk of autism for their children. 

Still, the 300 percent increase in autism diagnoses over the past 20 years raises eyebrows and deserves an explanation. An estimated 1 in 31 eight-year-olds in the U.S. now has Autism Spectrum Disorder. Broken down by sex, that’s 1 in 66 girls and 1 in 20 boys. How the heck has autism grown so prevalent?

The causes of autism are maddeningly difficult to research, but scientists have pinpointed a number of explanations over the years, all of which have far greater evidentiary support than RFK, Jr.’s favored hypotheses. Here are five of them.

Changes in Diagnosis

Before 1943, autism didn’t exist. That’s because Austrian American psychiatrist Leo Kanner only recognized it as a distinct medical condition that year. Afterwards, infinitely more people were diagnosed with autism. Was this because nobody had autism before the 1940s? No, of course not. They simply weren’t recognized as having it. 

Something similar has been going on over the past twenty years. The disorder’s definition has significantly broadened, subsuming other distinct diagnoses into the broader category of Autism Spectrum Disorder. For example, the rate of intellectual disability diagnoses has collapsed as autism diagnoses skyrocketed. Researchers think that this phenomenon accounts for much of the increase in autism rates.

More Screening

Two to three decades ago, autism didn’t attract nearly as much attention as it does now. Public awareness has since risen significantly, thanks to widely successful public health programs and celebrities and media figures advocating for more screening. In 2007, the American Academy of Pediatrics urged that all children be screened for autism at 18- and 24-months. The autism rate rose by 50 percent three years later.

Older Parents

While diagnostic changes and screening likely account for almost all of the “rise” in autism, there are a few factors that might have genuinely increased its prevalence. Older parents at childbirth are likely the greatest contributor. The average age of parents in the U.S. at childbirth has risen about five years since the 1970s. Children of older parents are more likely to have genetic mutations, which could result in a developmental disorder.

Increased Survival Rates for Preterm Babies

Thanks to advances in medicine, babies born preterm that would have otherwise passed away can now survive. However, preterm birth is associated with a higher risk of developmental disorders, including autism. Now that more of these babies are living to adulthood, it follows that there will be more people living with autism as well. 

Higher Rates of Obesity

Obesity rates in the U.S. have tripled since the 1960s. The weight condition is associated with all sorts of health issues, including autism. Children born to obese parents are more likely to eventually be diagnosed with Autism Spectrum Disorder. Interestingly, the link is far stronger for obese fathers than for obese mothers.

 
Join the discussion...