Sweeping Study Points To Genetics As Biggest Factor In Autism Risk

The study looked at more than two million people across five countries to determine what causes autism

There has been ongoing research for decades looking into the possible causes of autism spectrum disorder (ASD). A new study of more than two million people has yielded some remarkable findings that may help provide answers to doctors, researchers, and parents alike.

The study — the largest to date — published in JAMA Psychiatry this week found that autism spectrum disorders are over 80 percent reliant on inherited genes, meaning just under 20 percent of cases are caused by environmental factors. This could mean major opportunities for genetic research into the disease which, according to the CDC, impacts about 1 in 59 individuals (and is four times more common in boys).

Researchers looked at people from five countries (Denmark, Finland, Sweden, Israel, and Australia) and found, “Everywhere we looked, in five different samples, what we saw was that genetic factors were most important,” study author Sven Sandin, told HuffPost.

This is a significant finding given the cause of ASD has been linked to air pollution, maternal factors like weight and delivery method, a viral infection, or the wholly disproven MMR vaccine hypothesis.

Researchers looked at the medical histories of more than 2 million children between 1998 and 2012, tracking them until they turned 16 years of age. Of that group, just over 22,000 went on to develop an autism spectrum disorder. Through the national health registries, researchers analyzed the records of children’s parents, siblings, and other family members and specific genetic connections to come to their conclusions.

“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,” Sandin said. “This does not mean that we can completely ignore the environmental risk factors and their interaction with the genetic risk factors.”

The findings are consistent with results from a large 2017 study of twin and non-twin sibling pairs conducted in Sweden, suggesting about “83 percent of autism risk is inherited.”

It’s long been known that genetic factors play a part in developing ASD but the sheer size of this study indicates just how large a role it plays. “There is a lot of work that still needs to be done,” Sandin said. “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.”