Autism and Genetics: A Closer Relationship Than We Thought?

A new study involving twins appears to show the clearest evidence yet that autism stems from genetic causes, but why is this kind of research important, and how do we put these findings in context?

The study, by researchers from King’s College London and published online at JAMA Psychiatry, involved researchers investigating the lives and health records of twins born in England and Wales from 1994 through to 1996. The twins, some identical some non-identical, were assessed and recruited for the study from a wider data gathering effort using several different measures, including “the Childhood Autism Spectrum Test (CAST) (6423 pairs; mean age, 7.9 years), the Development and Well-being Assessment (DAWBA) (359 pairs; mean age, 10.3 years), the Autism Diagnostic Observation Schedule (ADOS) (203 pairs; mean age, 13.2 years), the Autism Diagnostic Interview–Revised (ADI-R) (205 pairs; mean age, 13.2 years), and a best-estimate diagnosis (207 pairs),” the study abstract notes. 

What the researchers found when they looked at the data this yielded was that autism was far more likely to affect both identical twins rather than both non-identical twins. This leads researchers to conclude that genes may account for upwards of 70 percent of autism cases. The researchers also noted that while shared environmental factors did still sometimes appear significant, this was no where near as strong as shared genetic factors.

Lead author Beata Tick is quoted as saying, ”Our main finding was that the heritability of ASD was high. These results further demonstrate the importance of genetic effects on ASD, despite the dramatic increase in prevalence of the disorder over the last 20 years. They also confirm that genetic factors lead to a variety of autistic skills and behaviors across the general population.”

The study is particularly useful because it compares identical and non-identical twins, meaning that we can get a sharper focus on precisely how autism might manifest. This research suggests that there may be very specific combinations of genes that lead to the group of characteristics we call autism, something that identical twins would share but not non-identical twins who may instead have certain hereditary similarities but not to the same extent.

One of the central problems doctors face in investigating autism is that autism isn’t just one condition. Autism is a spectrum disorder that has been pinned to certain key traits, like altered-state behavior, a reluctance to socialize, learning difficulties and more, but going from patient to patient it doesn’t necessarily look the same and, indeed, may be overlooked at the less extreme end of the spectrum because it includes a collection of traits that are also found in the general population–traits that we all might have like fastidious attention to detail, rigid logical thinking, social anxiety and more.

As such, looking at the genetic underpinnings of autistic behavior and identifying which genes are common to all presentations of the disorder can help us understand more accurately what groups of genes may contribute to its development, something that can help give us clarity on precisely what autism is and how we might best tackle it.

People point out that autism can’t solely be genetic in cause simply because of the sharp increase in diagnoses in the past few decades–a pace that is far too fast for genetic factors to make up the whole story. There are two answers to this, and it’s likely that only together are we getting a clear picture of what is going on.

The first and simplest answer is that we’ve just got better at diagnosing autism. Previously, people with autism would simply be labeled as learning-impaired or, in the most unfeeling context, might be labeled “bad” or “problem” children because of their inability to socialize and process stimuli in the way expected of them. Now, we hopefully know better and diagnosing autism has become more exact and, hopefully, more caring.

The second is that there may very well be environmental factors that can increase the chances of a child developing autism. Other studies have shown a correlation between pregnant women being exposed to certain particulate matter in the air due to pollution, and a moderate-to-substantial increase the likelihood of their children later being diagnosed with autism. Other studies have identified similar environmental factors that appear to affect the chances of a diagnosis later in life. I feel it necessary to highlight, though, that there is no evidence that vaccinations are among such environmental factors. However, the research-backed environmental factors cannot be ignored or dismissed just yet.

Essentially, this research seems to clarify that while environmental factors may still play a part in developing autism, it appears more likely that genetic factors are by far the more likely culprit. However, this doesn’t bring us any closer to actually finding out what genes may contribute to autism spectrum disorder and how we might combat their severe effects, and so there’s still a great deal more work to be done.

Photo credit: Thinkstock.


Siyus Copetallus
Siyus Copetallus3 years ago

Thank you for sharing.

dagmar karin dag
dagmar karin dag3 years ago

Interesante,pero necesita mas investigacion

Janis K.
Janis K3 years ago

Thanks for sharing.

Danuta Watola
Danuta W3 years ago

Thank you for this very interesting article.

Maureen Heartwood

Who is this "we" who thought autism wasn't mostly genetic? Nobody who's been following any of the research in the last ten years. Some of the gene markers have been identified already, and the work continues.

The supposed link to vaccines has been disproven so many times it isn't funny. It's also not funny when children die because they weren't vaccinated, or die of alternative autism therapies like chelation.

I'm not knocking this finding, but I wish research would find a way to help people gain scientific literacy and stop falling for harmful scams.

Natasha Salgado
Past Member 3 years ago


Nikki Davey
Nikki Davey3 years ago

Not good news for anti-vaxxers then.

Ana R
ANA MARIJA R3 years ago

Thank you for the article and some comments.

Nimue Pendragon

I had heard this a few years back. Thanks for the story.

Carole R.
Carole R3 years ago

Interesting post
Thank you