Genetics by far the biggest factor in autism risk, study says

For decades, researchers and parents have searched for clues about what causes autism spectrum disorder (ASD), which now affects about 1 out of every 59 children in the United States.

Now, a sweeping new study looking at more than 2 million people from five countries (Denmark, Finland, Sweden, Israel and Australia) found that about 80% of an individual’s risk of developing autism comes from inherited genetic factors and not from “environmental” influences, meaning anything other than changes to a gene’s DNA.

“Everywhere we looked, in five different samples, what we saw was that genetic factors were most important,” study author Sven Sandin, a statistician and epidemiologist with the Karolinska Institutet in Sweden, told HuffPost in an email.

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Notable people with Autism and Asperger's syndrome
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Notable people with Autism and Asperger's syndrome

Actor Dan Aykroyd revealed that he was diagnosed with Tourettes and Asperger’s syndrome after being diagnosed in the 1980s. 

“I also have Asperger’s but I can manage it. It wasn’t diagnosed until the early eighties when my wife persuaded me to see a doctor. One of my symptoms included my obsession with ghosts and law enforcement — I carry around a police badge with me, for example. I became obsessed by Hans Holzer, the greatest ghost hunter ever. That’s when the idea of my film Ghostbusters was born," he said

While filmmaker Tim Burton hasn't publically discussed it, his ex-wife Helena Bonham Carter has spoken about the artist possibly being on the spectrum. 

"We were watching a documentary about autism and he said that’s how he felt as a child," Bonham Carter said in an interview. "Autistic people have application and dedication. You can say something to Tim when he’s working and he doesn’t hear you. But that quality also makes him a fantastic father, he has an amazing sense of humor and imagination. He sees things other people don’t see.”

Jerry Seinfeld revealed to Brian Williams in 2014 that he believe's he's "on the spectrum." 

"I think, on a very drawn-out scale, I think I'm on the spectrum," Seinfeld said

"You know, never paying attention to the right things," says Seinfeld. "Basic social engagement is really a struggle," he explained. "I'm very literal. When people talk to me and they use expressions, sometimes I don't know what they're saying. But I don't see it as dysfunctional. I just think of it as an alternate mindset."

Singer Susan Boyle revealed in 2013 that she was diagnosed with Aspergers. 

"It was the wrong diagnosis when I was a kid," she said. "I was told I had brain damage. I always knew it was an unfair label. Now I have a clearer understanding of what's wrong and I feel relieved and a bit more relaxed about myself," " the singer said.

"It’s a condition that I have to live with and work through, but I feel more relaxed about myself. People will have a greater understanding of who I am and why I do the things I do."

Actress Daryl Hannah has Asperger's, which she was diagnosed with when she was a child. 

"Going to the Academy Awards was so painful for me. I'd almost faint just walking down the red carpet. I was so socially awkward and uncomfortable that I eventually got blacklisted," she said in 2010

"American Idol" star and singer James Durbin has been very public about his Tourettes and Asperger’s syndrome.

“I had no one to look up to like this growing up,” he said to People in July 2016. “When I was a kid, I knew I was different. I liked things no one else liked, and I was always very angry about having this. I hated it and wished it would go away. But now I want to be living proof that different is awesome.”

The "Community" and "Adult Swim" creator Dan Harmon said he discovered he has a form of Asperger's while doing research for the character Abed. 

He said in 2011, "I started looking up these symptoms just to know what they are. And the more I looked them up, the more familiar they started to seem.” 

Comedian Hannah Gadsby was diagnosed with autism "a few years back," and since then, the Australian native has been open about her process coming to terms with the diagnosis. 

"Once I got diagnosed, there was a certain amount of grief and confusion. Because when you think, 'oh now I have this framework,' and it was crystal clear as soon as I got diagnosed," she explained

 "The understanding of things just started falling into place and I was like, 'yep.'"

After marrying in 2018, comedian Amy Schumer revealed during her second Netflix special that her husband Chris Fischer has Asperger's.

"My husband was diagnosed with what used to be called Asperger's. He has autism spectrum disorder. He's on the spectrum. And there were some signs early on," the star said during her show. "It dawned on me how funny it was, because all of the characteristics that make it clear that he’s on the spectrum are all of the reasons that I fell madly in love with him.”

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That might sound surprising to mothers and fathers who for years have read story after story emphasizing possible risk factors from air pollution to the overwhelmingly discredited (but enduring) vaccine hypothesis. And indeed, experts say the media and public have been disproportionately focused on the role of modifiable contributors to autism, when genetics are the major driving force.

Here’s what parents need to know.

Genes are the biggest risk factor, but there are still lots of questions about which ones.

In the new study, published in JAMA Psychiatry on Wednesday, Sandin and his co-authors used models to analyze population data from five countries that included more than 2 million people, more than 22,000 of whom had been diagnosed with autism. Looking at outcomes among family members and weighing them against factors such as shared environments and their specific genetic connections led to their conclusion that inherited genes account for about 80% of the risk of autism in children with the disorder.

That’s pretty much in line with similar recent studies that have suggested genes are the major contributing factor to ASD. What’s notable about this new investigation, however, is its sheer size.

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Kaspar, a robot developed to improve the lives of children with autism
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Kaspar, a robot developed to improve the lives of children with autism
Harrison, 5, who is autistic, plays with Kaspar, a child-sized humanoid robot developed at the University of Hertfordshire to interact and help improve the lives of children with autism, in Stevenage, Britain January 30, 2017. REUTERS/Matthew Stock
LONDON, ENGLAND - NOVEMBER 29: Robotics PhD student Luke Wood works on KASPAR, a robot built at the University of Hertfordshire to help autistic children, in the Robotville exhibition at the Science Museum on November 29, 2011 in London, England. The Science Museum's Robotville exhibition showcases 20 unique and cutting-edge robots from European research laboratories, it is free to enter and runs from December 1-4, 2011. (Photo by Oli Scarff/Getty Images)
Dr. Ben Robins, Senior Research Fellow at the University of Hertfordshire, mediates while Harrison, 5, who is autistic, plays with Kaspar, a child-sized humanoid robot designed to interact and help improve the lives of children with autism, in Stevenage, Britain January 30, 2017. REUTERS/Matthew Stockman
Harrison, 5, who is autistic, plays with Kaspar, a child-sized humanoid robot developed at the University of Hertfordshire to interact and help improve the lives of children with autism, in Stevenage, Britain January 30, 2017. REUTERS/Matthew Stockman
Dr Mick Walters of the University of Hertfordshire looks at the University's KASPAR humanoid robot which is used to study human-robot interactions, one of the aims of which is to help autistic children. (Photo by Tim Ireland - PA Images/PA Images via Getty Images)
Harrison, 5, who is autistic, plays with Kaspar, a child-sized humanoid robot developed at the University of Hertfordshire to interact and help improve the lives of children with autism, in Stevenage, Britain January 30, 2017. REUTERS/Matthew Stockman
REPEATING CORRECTING TYPO IN BYLINE Kaspar, a child-sized humanoid robot developed at the University of Hertfordshire to interact and help improve the lives of children with autism is seen at the University of Hertfordshire, in Stevenage, Britain January 30, 2017. REUTERS/Matthew Stock
REPEATING CORRECTING TYPO IN BYLINE Dr. Ben Robins, Senior Research Fellow at the University of Hertfordshire, mediates while Harrison, 5, who is autistic, plays with Kaspar, a child-sized humanoid robot designed to interact and help improve the lives of children with autism, in Stevenage, Britain January 30, 2017. REUTERS/Matthew Stock
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“What’s immense about this study is the number of children across the world that were [included] — two million in the study population — and the large span of time, of a 16-year follow-up,” Dr. Wendy Sue Swanson, a pediatrician with Seattle Children’s who did not work on the study, told HuffPost. “It’s hard to argue with the kind of tonnage of that number.”

Of course, researchers have known for decades that genetics contribute to ASD. But now that they are grappling with just how significant a factor heredity is, there’s mounting pressure to determine which specific genes contribute in which specific ways.

And for now, that’s largely a question mark.

“There is a lot of work that still needs to be done,” Sandin told HuffPost. “We still do not know which specific genes contribute to risk. Also, there are numerous potential environmental factors that could be related to ASD either directly or acting together with genes. We have, so far, only been scratching the surface.”

That doesn’t mean modifiable factors don’t have an impact.

“If I were going to walk away after reading this study and talk to a family ... I’d say, ‘OK, we still don’t know the other 20%. It’s fairly controversial, what makes up the modifiable part,’” Swanson said.

Although they’re often called “environmental” influences in the scientific literature, these factors go beyond things like the potential impact of chemical exposures on a person’s likelihood of developing autism. Researchers are probing the possible role that everything from diet to infection during pregnancy might play. For now, the studies are ongoing. There just is not much that autism researchers and pediatricians can say in the way of, “If you avoid XYZ, you will decrease your child’s risk of developing autism.”

In an editorial that accompanied the new study, a team of three autism and psychiatry experts said the media has focused disproportionately on those environmental factors, perhaps because they are modifiable. An understandable pull exists to focus on the things that parents might be able to control to a certain extent. But that may have contributed to an incorrectly skewed sense of how much nature versus nurture contributes to the autism risk.

“Where we’ve gone awry is pointing fingers at things that don’t cause autism,” Swanson said. “Look at where we are right now with measles, mumps, and rubella vaccine trust and look at where we are with outbreaks because there was erroneous, falsified, misinformation that for decades led parents to believe vaccines were causing autism spectrum disorders.”

Being aware of family risk can help with early intervention.

Expectant parents who know they have some family history of autism might want to consider speaking with a genetic counselor if they have concerns, Swanson said.

Being aware of family history and how it might contribute to a child’s autism risk also can help parents and pediatricians be mindful of early signs of autism as they arise. Research clearly shows that early interventions, which can begin as early as age 2, can help improve physical, emotional, and communication skills.

“On some level, I feel like we should feel comforted by [these findings]. Because it’s almost like autism is explained ... it’s not because of what a parent is doing right or wrong,” Swanson said. “It is largely based on a child’s genetic makeup.”

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