On RFK, Jr. on Autism

Reactions from Jill Escher, Cremieux Recueil, and Emily Oster

Jill Escher (henceforth JE), Cremieux Recueil (henceforth CR), and Emily Oster (henceforth EO) each reacted to a recent speech by RFK, Jr. about autism.

All agree that the cause of autism is probably genetic. The cause is likely not environmental, and it is almost certainly not vaccines.

There is disagreement concerning whether to regard the rise in autism cases as a real phenomenon or merely an diagnostic epidemic. Let me start with that question.

JE writes,

For example, the California Department of Developmental Services, well-known for its robust data on the more disabling forms of autism, counts a mere 60 cases of autism in residents born in 1954—Kennedy’s birth year. Compare that to 5,163 cases identified in kids born in 2010. It’s important to note that this system has not expanded its eligibility criteria and, in fact, enacted more stringent requirements in 2003. It has seen its overall autism caseload soar from about 3,200 in 1989 to about 190,000 today.

Looking at that same study, CR writes,

For starters, the ages in the most recent cohorts are young—they’re children—but in the oldest cohorts, we’re talking about adults whose data wasn’t gathered by the CDDS when they were kids, but instead much later, long after these people had made it to adulthood, when diagnosis is frequently neglected.¹ Autism is also associated with shorter lifespans, which are even shorter for the people with the most severe manifestations of the condition. Accordingly, many of the oldest autistics would have already died off by the time the CDDS got around to surveying. These biases deflate the rate of autism the further back you go, exaggerating the subsequent increase.

…Because autism was regarded as particularly severe prior to the DSM treatment of it and those whose condition goes unnoticed by adulthood likely aren’t severe cases, and because there was practically no incentive to diagnose until the most recent generations, that meant it was diagnosed rarely, making subsequent increases that much more exaggerated.

EO writes,

the majority — possibly the large majority — of the change over time is due to changes in how we diagnose and in awareness. What is missing is a concrete answer to whether this is 60%, 80%, 95%; this feels like a very important research question, which I hope someone is working on.

Is Autism Mostly Genetic?

JE, CR, and EO all see autism as mostly genetic. EO writes,

A meta-analysis of studies like this shows a heritability factor between 65% and 90% — meaning genetic causes explain the majority of variation across the population, possibly almost all of it. There is not a single gene for autism, but there are many genes that contribute.

JE writes,

I have long advocated for research on new concepts about autism’s origins. This relates to how toxic exposures impact not the fetus, but the parents’ germ cells—that is, their eggs, sperm, and precursor cells. There is vast scientific territory open for exploration here.

This gestures toward a challenge in distinguishing genetic from environmental factors. If autism is caused in part by mutations that take place during pregnancy, can those be explained by environmental factors?

CR writes,

Though no one has ever provided quality evidence for an environmental cause of autism, there may still be at least two things that could be causing slightly—but not massively—rising rates of autism. These are

1. Older parents. The age at first marriage and the age at first childbirth are increasing, and this seems to have a causal effect on children’s risk of autism. Could this be environmental, driven by the womb? Maybe, but since the paternal age effect is larger, it seems like the age-related accumulation of mutations in sperm will be more likely to take the blame.

2. Our increasingly awesome healthcare systems. People who would never have survived childbirth or early childhood in previous generations are surviving nowadays at historically unprecedented rates. The examples range from those with major congenital defects to people with minor, but still risk-disposing issues, like autism

Related to these, EO writes,

On average, fathers over 50 are slightly more likely to have children with autism. It is difficult to know how much of this relationship is causal, as opposed to correlation. But even if this relationship is causal, the share of fathers in this age group has increased only a tiny bit over time, probably not enough to be an important part of the explanation.

A second explanation is prematurity. Babies born preterm, especially very preterm, are much more likely to have autism. Those born between 22 and 27 weeks are about six times as likely to be diagnosed as children born full-term. Over time, survival at these very early gestational ages has increased. Again, though, the share of babies here is just too small to be an important part of the overall trend.

For better health care to increase the incidence of autism, the health care must increase the survival rate of potentially autistic fetuses relative to non-autistic ones.

A few years after I was born, my mother had a miscarriage. With today’s medicine, I definitely would have had a sibling.¹ Now, suppose that genetically the chances that my sibling would have been autistic were relatively high. My parents were spared that risk, but parents nowadays would have such a child, because of better modern medical care.

Note that we are speculating about factors that would increase the true incidence of autism, not just an increase in diagnoses. But if CR and EO both read the studies as showing that much of the increase is in diagnoses, I am inclined to go with them.

Note that EO sees the increase in diagnoses as cause for celebration: more people getting treatment. CR sees it more as a cause for cynicism: more service providers getting paid.

Is the increase in diagnosis a case of more true positives (EO’s implicit view) or a case of more false positives (CR’s implicit view)? I am reluctant to step into that argument. It is not like there is a blood test you can use to show the presence or absence of autism. And there are many patterns of behavior that some clinicians would say indicate autism but other clinicians would say indicate something else.

What I do believe is that, whether you call it autism or not, serious behavioral and social deficits are more widespread in children today than fifty years ago. My impression (not based on data) is that if you could time travel back to a statistically representative first grade cohort in 1960 and compare it to a statistically representative first grade cohort in 2025, this difference would be clearly visible.

Finally, a late addition to this post. Josh Zlatkus writes,

I suspect that many things only become a problem after a solution is available.

Pointer from Rob Henderson. The point is that we do not focus concentrate on problems for which we have or think we can find a solution. As long as behavioral problems with autism were untreatable, we didn’t have a name for that syndrome.

substacks referenced above: @

Modern Wisdom, Sex and Violence, Parental Narcissism

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The Solution Problem (Part 1/3)

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Trump, RFK, and the Autism Dilemma

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What’s the Deal With Autism Rates?

1. My mother did not receive a rhogam shot after her first pregancy, because the phenomenon of RH incompatibility was not well understood in the early 1950s. For decades now, such an injection has been standard for mothers with the RH incompatibility factor that my mother had with my father.