Is the government studying autism?
Health Secretary Robert F. Kennedy Jr. last month launched a “massive testing and research effort” that he says by September will reveal the mystery of what causes autism— and what is behind a surge in diagnosed cases. Kennedy, who has for years promoted the discredited claim that vaccines cause autism, didn’t mention childhood shots when announcing the study. But he proclaimed his certainty that an “environmental toxin” is behind rising case numbers, and said scientists will look at food additives, mold, pesticides, medicines, ultrasound scanning, and other potential factors. “This is a preventable disease,” Kennedy said. “We know that it’s an environmental exposure.”
Experts say his claims are deeply flawed. The overwhelming majority don’t believe that autism—a neurological and developmental disorder with a range of symptoms that typically include impaired communication and social skills—is caused by environmental factors. And while autism rates are trending higher, “it seems very unlikely that it is an epidemic, in the way that people define epidemics,” said Catherine Lord, an autism researcher at University of California, Los Angeles.
Have rates climbed significantly?
Autism incidence in the U.S. has gone from 1 in 150 children in 2000, to 1 in 54 in 2016, to 1 in 31 in 2022, according to the CDC. But experts believe much or all of this rise is due to improved diagnosis and a broadening of the criteria for who qualifies as autistic. There’s no blood test or brain scan that can detect autism spectrum disorder; diagnoses come through observation, with universal screenings recommended since the 1990s for 18 and 24 months. Experts say clinicians and parents have become better attuned to symptoms and that cases that once would have been labeled as mental retardation and language disorders now fall under ASD. “You’re capturing more subtle presentations,” said Roma Vasa, a psychiatrist at Johns Hopkins University School of Medicine. There is evidence to back this up. Severe cases involving non verbal children, which are easily diagnosed, have held steady. And there’s been a disproportionate rise in cases among Black and Latino children, which could correlate with improved access to diagnostic services. But exactly what causes autism is not yet clear.
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What do we know?
Scientists say the primary cause of autism is genetic, with environmental factors playing a secondary role. Powerful evidence of this can be seen in studies of twins. In identical twins, who share all their DNA, if one twin has ASD, the other typically does as well. And in fraternal twins, who share about half their DNA, if one twin has autism, the chance the other will also ranges from 53 percent to 67 percent, according to a review of studies. Researchers have identified more than 250 genes associated with elevated odds of ASD, and linked most autism cases—about 80 percent—to inherited genetic mutations and at least another 10 percent to noninherited mutations. While autism generally surfaces during toddler hood, experts believe it is “established in the earliest stages of brain development, in the womb,” said Mady Hornig, an epidemiologist at Columbia University. It’s possible that environmental factors may play a contributary role in utero.
What types of factors?
Numerous studies have linked maternal exposure to air pollution, especially late in pregnancy, with higher risk of an autistic child. It’s suspected that ultrasmall particles of fossil fuel pollution may trigger biological cascades that effect brain development, and that individuals with a genetic predisposition to autism are more vulnerable to these harmful effects. Researchers have examined other toxins. A UCLA study found that pregnant mothers who live near farms that spray commonly used pesticides were up to 16 percent more likely to have children diagnosed with autism than those who live farther away. Vitamin deficiencies could also play a role: Several studies have noted a lowered autism risk among pregnant mothers who took folic acid, or vitamin B9; in a 2013 Norwegian study, the drop was almost 40 percent. Scientists have also drawn connections between autism and certain physiological risk factors in parents.
How strong are those links?
There seems to be a powerful correlation between autism and parental age, especially among children born to older fathers. An Israeli study found that children fathered by men in their 40s or older were six times more likely to have autism or related disorders than those fathered by men younger than 30. Preterm births may also be a predictor for autism: A study of 4 million births in Sweden found that a child born between 28 and 33 weeks is about twice as likely to be diagnosed with autism than one born at full term, and that those born between 22 and 27 weeks are four times as likely to be diagnosed. Meanwhile, a study of Swiss mothers showed that those who’d been hospitalized for an infection during pregnancy were 37 percent more likely to have a child with autism. All these findings indicate “autism is an extraordinarily complex condition,” said Hornig, “probably influenced by hundreds of genetic, environmental, behavioral, and dietary factors.”
Might RFK Jr.’s study shed any light?
Odds are low at best, say scientists. Properly conducted, such an effort would require years, not months. And the study’s premise, that a sole environmental cause can be found and eliminated, refutes everything known to date about autism. We’re dealing with “the complexity of the formation of the human brain,” said Janine LaSalle, a professor of microbiology and immunity at University of California, Davis. “If there were a single smoking gun, it would have been found by now.”
An enduring myth
More than a dozen major studies involving hundreds of thousands of children across three continents have proved comprehensively that vaccines do not cause autism. But the idea of a link between childhood shots and autism—in particular the measles, mumps, and rubella vaccine—has shown dogged staying power. A recent Gallup survey found 13 percent of Americans believe in the connection and half were unsure. The fears over MMR date to 1998, when British doctor Andrew Wakefield published an article in The Lancet tying vaccines to autism in a dozen children he studied. Scores of problems were found with the study, which was retracted by the journal. But “the cage door got open, and the devil came out,” said vaccine expert Paul Offit. Scientists note several reasons the debunked theory has such legs, including that the first MMR dose is given between 12 and 15 months—around the time autism typically emerges. And blaming vaccines for causing autism gives parents a simple explanation for a condition that continues to puzzle scientists. Whatever the cause is, said UCLA autism researcher Lord, “it’s not vaccines.”
