Here’s how much genetics plays in a role in autism

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While scientists are still discovering more about autism spectrum disorder (ASD), new research in the field suggests that genes may explain most of the risk of an ASD diagnosis – to the tune of 83 per cent.

American scientists say they’ve calculated the most accurate figure to date for measuring the exact role genes play in autism cases. Turns out, inheriting certain genetics may explain “most” of the risk.

The findings come from re-analyzing data on a group of children in Sweden – they included 37,570 twins, 2.6 million siblings, and 432,000 half-siblings whose health was tracked from 1982 through to 2006.

After scouring through their health records and susceptibility to ASD, the scientists found that the likelihood of being diagnosed with autism is largely based on inherited genes.

READ MORE: 4 misconceptions about autism

“This estimate – 83 per cent – is slightly lower than the approximately 90 per cent estimate reported in earlier twin studies and higher than the 38 per cent estimate reported in a California twin study, but was estimated with higher precision. Like earlier twin studies, shared environmental factors contributed minimally to the risk of ASD,” Dr. Sven Sandin, the study’s lead author out of Mount Sinai Hospital in New York, wrote.

Autism was first described by scientists in the 1940s. Years later, critics pointed a finger at cold parenting – “refrigerator mothers” who were distant and didn’t engage with their kids – as the culprit.

While researchers still don’t know what causes autism, they’re certain parenting isn’t a factor. They’re zeroing in on genes instead.

Studies have suggested that parents who have a first child with autism have higher chances of having a second child with autism compared to the general population.

READ MORE: U.S. autism estimate increases to 1 in 68 children

The study took this into account: the scientists didn’t consider a single moment in time for siblings but noted that one sibling could be diagnosed first, while the other would be diagnosed later.

Dr. Charis Eng, a Cleveland Clinic expert who wasn’t involved in the study, said this doesn’t mean one single gene can be altered to cause all autism. Instead, she said various genes could be at play, and that the environment is still a factor, too.

But the findings are an important step in zeroing in on an important risk factor.

“Taking a family health history would be important, because if there’s already someone with autism spectrum disorder, and the study is correct, then the likelihood of another person having it in the family is higher,” Eng said.

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“It’s not a lot higher, so people should not panic, but it just gives an indication. If people are unsure about their autism risk, they should not hesitate to ask to see an autism doctor or a genetics professional.”

She said she hopes more families with loved ones who have autism sign up for research.

Canadian scientists who studied siblings with autism and their parents found that even siblings can have different “forms” of autism.

In this case, the siblings and their parents’ genetic code were examined. Mutations present like typos in the human DNA code. While siblings shared autism spectrum disorder and the same parents, the typos in their DNA that led to the neurodevelopmental condition weren’t the same.

Autism is a neurological disorder marked by abnormalities in the brain.

While people believe that those with autism lack empathy and can’t develop meaningful relationships, they can feel as much, if not more, than their peers.

READ MORE: Autism may be linked to faulty prenatal brain growth, small study says

Children with autism may find it difficult or aren’t sought out by others. They could have difficulty relating and building connections with their peers, Autism Canada says.

One in 68 children falls under the autism spectrum disorder, according to the Centers for Disease Control and Prevention (CDC). The U.S. federal agency says that’s a 30 per cent jump from its last estimate of 1 in 88 children – the latest calculations mean autism is more than twice as common as officials said it was years ago.

READ MORE: Autism, even in siblings, has different genetic causes, Canadian study suggests

The CDC says that autism affects 1.2 million U.S. children and teens. U.K. health officials say one in every 100 people is living with autism.

Health Canada points to global statistics – “an average prevalence” of about one per cent – but it’s working on a national surveillance system for autism. The first collection of data is expected in 2015 with initial findings to be made available by 2016.

Autism affects one out of 42 boys and one in 189 girls, according to estimates.

carmen.chai@globalnews.ca

Follow @Carmen_Chai

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