Vaccines don't cause autism. What does?

NBC News

22-11-2024

Robert F. Kennedy Jr.'s false claims linking autism to childhood vaccinations are receiving new scrutiny now that President-elect Donald Trump has selected him to lead the Department of Health and Human Services, a sprawling agency with a budget of $1.7 trillion that oversees research into both autism and vaccines.
The myth that autism is caused by childhood vaccines — proposed in 1998 by a British doctor who was later banned from practicing medicine in the United Kingdom — has been thoroughly debunked. Hundreds of studies have found vaccines to be safe. The World Health Organization estimates that over the past 50 years, immunizations have saved 154 million lives around the world.
Kennedy, who espouses a number of health-related conspiracy theories, has pointed to vaccines to explain the substantial rise in autism diagnoses in recent decades, which have ballooned from an estimated 1 in 150 children in 2000 to 1 in 36 today. Research suggests that much of that increase is due to increasing awareness and screening for the condition; changing definitions of autism to include milder conditions on the spectrum that weren't recognized in previous years; as well as advances in diagnostic technology.
'For a very long time, the anti-vaccine movement has been exploiting families of autistic people, promoting a market for pseudo-scientific treatments that don't provide the answers they're looking for and that can expose autistic people to real harm,' said Ari Ne'eman, co-founder of the nonprofit Autistic Self Advocacy Network and an assistant professor of health policy and management at the Harvard T.H. Chan School of Public Health. 'More discredited conspiracy theories linking autism and vaccines are not the answer.'
Timothy Caulfield, research director at the University of Alberta's Health Law Institute in Canada, who studies health misinformation, said that people often are more willing to believe conspiracy theories about conditions such as autism, whose causes are complex and not fully understood, than diseases with clear causes.
People seem less inclined to speculate, for example, about alternative explanations for Down syndrome, which causes intellectual disabilities and has long been known to be caused by an extra copy of chromosome 21.
'It's really a shame because there are vulnerable families [of people with autism] who need our support,' said Judith Miller, a clinical psychologist and senior scientist and training director at the Center for Autism Research at Children's Hospital of Philadelphia. 'Every dollar and hour spent trying to debunk a conspiracy theory is a dollar and an hour lost that could have been spent trying to understand how to help families.'
A complex condition
Finding the causes of autism is complicated, because it's not a single disorder, said Manish Arora, a professor of environmental medical and climate science at the Icahn School of Medicine at Mount Sinai in New York.
'Autism is a spectrum, not a single narrow disease,' Arora said. 'It's many, many things under one umbrella.'
Although people diagnosed with autism often have similar strengths and challenges, 'there are many paths to autism and many presentations of autism,' Miller said.
Scientists have found a variety of risk factors for autism — most of which exist before birth — but there is no single cause for a neurological and developmental condition that affects how people interact with others, communicate, learn and behave.
A number of the traits sometimes seen in people with autism — such as being sensitive to loud noises, for example, or finding it difficult to interpret social cues — are also found in people who have not been diagnosed with autism. Doctors diagnose autism based on a person's behavior, noting that there is no simple test for the condition, as there is for Covid or diabetes, said Arora, founder and CEO of a start-up company that researches biomarkers for autism and other neurological conditions.
Finding the cause of an infectious disease — such as influenza, which is caused by the flu virus — is much more straightforward.
While researchers continue to study the factors that influence the development of autistic traits, 'the one thing we know doesn't cause autism is vaccines,' said Catherine Lord, a psychologist and researcher at the Center for Autism Research and Treatment at the UCLA David Geffen School of Medicine.
Genetic vulnerability
Doctors have long known that genes play a large role in autism, simply by noting that autism can run in families. For example, in identical twins — who share all of their DNA — if one twin has autism, the other usually does, as well. In the case of fraternal twins — who share about half their DNA — if one fraternal twin has autism, the chance that the other will have autism ranges from 53% to 67%, according to an analysis of research studies.
Scientists have identified more than 100 genes related to autism, Miller said, and genes are believed to play a role in 60% to 80% of cases.
'The genetics of autism have never been better understood,' said Dr. Gregory Cejas, medical director of the Autism Clinical Center and Fragile X Clinic at the Washington University School of Medicine. 'We're making leaps and bounds about known genetic causes of autism.'
Yet genes clearly don't explain every case of autism.
Autism is very different from conditions like sickle cell anemia or cystic fibrosis, which are caused by a single gene. Scientists believe that people develop autistic traits due to a combination of genetic vulnerability and environmental exposures, Lord said.
'People have found many, many different genetic patterns associated with autism, but none of them are only associated with autism and none of them are always associated with autism,' Lord said.
For example, fragile X syndrome — caused by a mutated gene on the X chromosome — is the most common known cause of autism. But only a fraction of children with the genetic mutation actually develop autism, Miller said. It's possible that this mutation leaves some people more vulnerable to developing autistic characteristics, while others with the same mutations don't develop autistic traits, because they are shielded by protective factors that have not yet been identified.
Some people blamed the measles-mumps-rubella vaccine with autism because symptoms of the condition often occur at around 12 to 15 months of age, the same time toddlers get that immunization. But Miller notes that 'most of the genetic conditions that affect our life and health aren't apparent at birth. Symptoms or characteristics won't show up until later, but the genetic code will have been with us the whole time.'
Prenatal vulnerability
Many of the known risk factors for autistic characteristics occur before birth or at the time of delivery, Arora said. Babies who experience complications at birth, such as their umbilical cord becoming wrapped around their neck, have a higher risk of autism.
So do babies born prematurely, perhaps because of something that happened in the womb.
Children are more likely to be diagnosed with autism if they have older fathers and possibly if they have older mothers, Miller said. It's not clear if something in the biology of older parents causes a child to have a higher risk of autism, or if socioeconomic issues could play a role. It's possible that older parents have better access to health care, making it more likely for their child to receive an autism diagnosis.
A mother's health influences her child's autism risk in several ways, according to multiple studies: Children have a greater chance of being diagnosed with autism if their mothers were exposed to high levels of air pollution or developed a serious infection, such as the flu or pneumonia, while pregnant.
While Ne'eman, of the Autistic Self Advocacy Network, said he's not opposed to basic biological research on autism or its causes, he said those studies do little to help people with autism overcome the barriers they face in their everyday lives.
He notes that only 8.4% of the $419 million spent on autism research in the United States is devoted to support and services for people with autism.
'We need an autism research agenda,' he said, 'that reflects the true priorities of autistic people and our families: supports across the lifespan and inclusion in the community.'