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Home » Genetics cause autism in new study – once again, it’s not about vaccines

Genetics cause autism in new study – once again, it’s not about vaccines

Let’s start right at the top – a new, powerful study has shown that mostly genetics cause autism. Despite the fear, uncertainty, and doubt from the anti-vaccine religion, we have overwhelming scientific evidence that vaccines are not linked to autism spectrum disorder (ASD). This is settled science

Almost all legitimate science researchers who focused on autism never bought into the vaccines link. Not only was there no evidence of this imaginary link (thanks to the cunning fraud Andrew Wakefield), when scientists went looking for a possible link, they never found one. 

However, investigators have been searching for legitimate underlying etiologies for ASD – the hypothesis that genetics cause autism has been the center of research for years. 

So let’s look at this study in detail so that we all have more evidence to shut down the vaccines and autism tropes. Well, at least we can try, since the pseudoscience that permeates the anti-vaccine world is resistant to scientific facts (see Del Bigtree). 

The study that shows genetics cause autism

The new study, by Sven Sandin et al. and published in JAMA Psychiatry, included 2 million individuals across five countries – Denmark, Finland, Sweden, Israel, and Western Australia. This cohort study (see Note 1), considered near the top of the hierarchy of biomedical research, is one of the largest of its kind. 

The study found that 80% of the risk for autism spectrum disorders are 80% reliant upon inherited genes. However, there are some complications to this genetic component. There are some de novo mutations, that is, new mutations not inherited from either parent and are caused by environmental issues, that are entangled with the inherited genes, making it difficult to determine just what specific genes are related to autism. 

genetics cause autism
This graphic shows the correlation of autism diagnosis the closer the familial relationship.

The study also found that maternal factors, such as a mother’s weight, mode or timing of delivery, and/or nutritional intake, hand minimal or nonexistent roles in the risk for autism.

Specifically, the researchers found that:

  • The median autism heritability for the whole cohort was estimated to be 80.8%.
  • For the Nordic countries combined (that is, Sweden, Denmark, and Finland), autism heritability was estimated to be from  81.2% to 82.7%.
  • Country-specific autism heritability was estimated to range from 50.9% in Finland to 86.8% in Israel.
  • Of the over 2 million individual births studied, between 1998 and 2013 depending on the country, 22,156 (the cohort) were eventually diagnosed with an autism spectrum disorder. The prevalence in this birth group was about 1.1%. 

According to WebMD

The findings could open new doors to research into the genetic causes of autism, which the U.S. Centers for Disease Control and Prevention now says affects 1 in every 59 U.S. children.

…”the current study results provide the strongest evidence to our knowledge to date that the majority of risk for autism spectrum disorders is from genetic factors,” said a team led by Sven Sandin, an epidemiological researcher at the Karolinska Institute in Stockholm, Sweden.

The new study might help dampen public interest in supposed — but unproven — “environmental” causes of autism, such as vaccines. Long-discredited, fraudulent data linking childhood vaccination with autism is still widely cited by the “anti-vaxxer” movement.

In a companion editorial on the new study, also published in JAMA Psychiatry, the authors wrote:

The study by Bai et al elegantly summarizes and confirms, using the largest data set to date, a key truth about ASD’s risk architecture: the disorder is strongly heritable, with environmental factors, although important, contributing relatively less to its variance than genetic factors. Where do we go from here?

They’re saying that environmental contributions to autism (like the debunked trope that vaccines cause autism) are significantly less critical that genetic contributions. 

Not what is done in real science. But more science than the anti-vaxxers do. Photo by Alex Kondratiev on Unsplash.

Genetics cause autism is not controversial

The authors set up their research by showing that numerous studies, including a meta-analysis, have shown that the genetic component for autism generally is around 80%.

A meta-analysis of twin studies estimated heritability to be in the range of 64% to 91%, and 3 population-based studies from Sweden recently estimated the heritability of ASD to be 83%, 80%, and 66%. Among those earlier heritability calculations from twin and family studies (eTable 1 in the Supplement), a single study has estimated maternal effects, reporting modest, if any, contribution to ASD. Estimates of the contribution of shared environment range from 7% to 35%, but multiple studies estimate the contribution to be zero. Thus, although the origin and development of ASD has been investigated for half a century, it remains controversial.

There is a strong body of evidence that has established that the bulk of the causes of autism is genetics. This is how science is done – it’s not one piece of evidence that matters, it’s all of the evidence. And Sandin et al. looked hard at all of the research and found that their hypothesis, “does genetics cause autism,” is supported not only by their data but also by others across the world. 

Genetics cause autism  ONLY 80% of the time

I know that the anti-vaccine activists will focus on this point – they’ll claim that genetics cause autism only 80% of the time, and the environment 20%. Using the odd math skills of the anti-vaxxers, they’ll round up 20% to 100% and round down the 80% to 0%. 

Of course, that’s an issue with almost all humans with risk assessment. Phil Plait (an astronomer, yes I have scientific interests well beyond vaccines and cancer) once wrote that the lifetime risk of being killed by a meteorite is about 1 in 700,000. That’s actually a higher risk than any major adverse event from vaccines, which is around 1 in 1,000,000.

I can now predict that the anti-vaxxers will start wearing steel helmets rather than tin-foil hats to protect themselves. 

The point is that a 20% risk from environmental causes for autism is substantially below the risk from genetics. But what’s going to happen is that the anti-vaxxers will blame vaccines for that 20% risk (obviously after rounding up to 100%) in spite of the vast mountain of evidence that has established, nearly conclusively, that vaccines are unrelated to autism. 

Oh wait, that’s already happened. David Gorski writes at Science-Based Medicine in detail about one of my favorite (not really) anti-vaccine pseudoscientists, James Lyons-Weiler, passing along misinformation and junk science about this study. 

I’m going to give some of the highlights, though, for a full review of Lyons-Weiler’s bovine feces, Dr. Gorski does it best. Here we go:

Not surprisingly, antivaxers do not like this study. The reason they don’t like it is because it is practically gospel among them that autism and ASDs are not primarily genetic conditions, but rather caused mainly by environment, specifically vaccines, although they frequently obfuscate by attributing the conditions to vaccines and “other environmental influences” and “toxins”. Also not surprisingly, first out of the gate (that I could find, anyway) to attack the study was James Lyons-Weiler.

We’ve met him before when he tried to attribute the death of a teenage boy to Gardasil. The sad thing is that Lyons-Weiler was once an actual reputable scientist (or at least not, to my knowledge, a disreputable one) who during his pre-antivaccine career directed two different bioinformatics cores, one at the University of Massachusetts in Amherst and the other at the University of Pittsburgh, the latter of which closed in 2014.

Since then, he’s gone all-in on antivaccine pseudoscience, even going so far as to form an institute he dubbed the Institute for Pure and Applied Knowledge (IPAK), which is about as arrogant-sounding a name for an institute as I’ve ever heard. IPAK isn’t just into antivaccine “science”, but that does seem to be its primary focus compared to others. Since then, Lyon-Weiler’s been battling it out with Leslie Manookian for the title of Most Antivaccineappearing on antivaccine panels with Del Bigtree, Gayle DeLong, Sherri Tenpenny, and Toni Bark, and, it appears, helping antivaccine pediatrician Paul Thomas carry out a “vaxxed vs. unvaxxed” study.

Just to be clear, “bioinformatics cores” isn’t a place where original research is done. It’s really just the group that essentially does all of the statistical analysis, while creating cute little graphics, for the real scientists. OK, that might be harsh, but it’s not far from what happens. When I did graduate research, back in the late Cretaceous, there were grad students in the math and computer information departments who helped us do the statistics and pretty graphs. 

Let me remind you – Lyons-Weiler is a false authority. He has zero experience, education, or published research in any science related to vaccines. Zip. Zero. Zilch. Because he has no evidence supporting his claims, either from his own research or from others, he is the perfect definition of false authority. 

But back to his criticisms. Lyons-Weiler lists out a bunch of complaints, that just isn’t that relevant, to criticize this study. Because Lyons-Weiler has a pre-ordained belief about autism, that it is caused by vaccines, he is incapable of accepting high-quality research published in real peer-reviewed journals unlike Lyons-Weiler’s use of predatory journals to publish his nonsense.

So, he published a laughably titled blog post, “Yet Another Highly Unethical and Socially Irresponsible “Genes-Only” Study Fails to Show that Autism is 80% “Genetic” with his complaints. And it seems like he doesn’t have access to the full article (all my links are to abstracts because JAMA annoyingly puts their studies behind a paywall – I actually read the full study), because he blasts the WebMD article to which I linked above:  

The article skips over the fact that the newest, latest study, like the prior studies, fails to actually measure the contribution of a single environmental factor. While the article rails against “anti-vaxxers”, the study ignores the vaccination status of those involved in the study. The mantra of so many studies never showing association has be tempered with a mature, responsible and realstic interpretation in the context of how those studies were conducted: restricted to one vaccine (MMR).

Once again, there are literally hundreds of peer-reviewed journal articles that have established, over and over and over, that there are no links between vaccines (especially the MMR vaccine). This study by Sandin et al., which wasn’t powered to look at the environmental causes, established that around 80% of the causal factors for ASD is genetics. 

Furthermore, Lyons-Weiler, because he lacks an understanding of epidemiological studies like this cohort study, he’s just ignorant of how these studies are structured and analyzed (specifically with statistics). Back to Dr. Gorski:

…the latter of those two examples reveals shocking statistical ignorance, as quite frequently, raw data reveal an effect that turns out to have been spurious when adjustments are appropriately made for confounding factors. Apparently, like Brian Hooker, Lyons-Weiler prefers the simplicity of the raw, unadjusted analysis that doesn’t control for confounders and provides false positive associations between vaccines and autism.

Lyons-Weiler’s next point that he must whine about is that he thinks the study wasn’t done in the way he wants:

Their entire methodology is based on familial correlations. In the current study under consideration, no exposure levels to pesticides, medical exposures in utero, smoking history, nothing environmental was measured. And yet somehow the study authors pretend they can estimate the % liability from environmental factors. How do they pretend to achieve such a feat?

That wasn’t the point of the study. Let me repeat, they wanted to find out what caused autism – genetics or environmental. And they found that over 80% was caused by genetics. Yes, we need to understand those environmental effects (and we almost absolutely know it’s not vaccines), but that’s a different study, one that’s much more complicated.

But again, back to David Gorski, who responds to this complaint:

This is just a diversion. Remember, if you accurately estimate the percentage of risk that is genetic, then whatever’s left over must include the environmental risk factors. You don’t have to measure exposure to each and every potential environmental risk factor.

Lyons-Weiler also seems to have a few odd beliefs about genetics and how it might be related to autism. As I mentioned above, the heritability of autism is complex. But one thing that he implies (and so do a lot of anti-vaxxers) is that if it is genetic, where is the one gene that causes it. 

It is not one gene. It could be hundreds of genes, the vast bulk of them are inherited from parents with some level of de novo mutations. 

Then Lyons-Weiler went off the rails (well, he went off the rails long ago, so maybe he’s off the planet in some magical world of pseudoscience). He pushes a concept called “phenomimicry,” which is a non-existent term (it’s so ridiculous that even Wikipedia, which has articles on all sorts of pseudoscience, doesn’t have an article). Phenomimicry claims that the environment can make changes in genes, proteins, and biological pathways in a way that it appears to be genetic.

Hang on. I just snorted my coffee.

Back to Dr. Gorski, because he hits the nail on the head:

Phenomimicry, if it exists, would indeed be a cool biological phenomenon, but basically here Lyons-Weiler is speculating wildly, pulling something out of his nether regions and using its lack in the study as a cudgel without telling us any plausible scientific rationale why the study authors should have even considered phenomimicry. It’s also a term that, as far as I can tell from Pubmed and Google, is only used by one person, Dorothy V.M. Bishop and is not a generally accepted concept. A PubMed search turns up only one article by Bishop using the term and Googling only turns up mainly articles referring to Bishop’s article.

Anyway, that’s enough of ridiculing Lyons-Weiler’s pseudoscience trying to dispute Sandin et al. article that carefully analyzes the data that establishes that genetics cause autism. I’m sure that other anti-vaccine quacks will jump in the fray, probably referencing Lyons-Weiler because he is their favorite false authority.

Obligatory cute animal photo. According to Lyons-Weiler the White Rabbit is a result of phenomimicry. 


We already knew that vaccines had nothing to do with autism. Nothing. We had a good idea that most genetics caused autism. Now, we have another article, that follows several others, which establishes the fact that around 80% of the cause of autism is genetics.

The anti-vaxxers hate this. But they never provide any real research that supports their beliefs. The pro-science side has a boatload of real clinical and epidemiological evidence, like this new article, that supports the fact that vaccines are safe and effective.

And for the one-billionth time, vaccines have nothing to do with autism, unless you’re a delusional, pseudoscientific quack with a Ph.D. in environmental science. Dr. Paul Offit, he is not. Not even close. 


  1. A cohort study examines one or more samples (called cohorts) which are followed prospectively over time. Subsequent status evaluations with respect to a disease or outcome are conducted to determine which initial participants exposure characteristics (risk factors) are associated with it.


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