Highest Autism Risk Down to Common Gene Variants

Common genes may be responsible for autism, according to a recent study published in the journal Nature Genetics.

Researchers found that close to 52 percent of autism risk could actually be traced back to common and rare inherited genetic variations, along with spontaneous mutations that contribute to 2.6 percent of the total risk.

"Genetic variation likely accounts for roughly 60 percent of the liability for autism, with common variants comprising the bulk of its genetic architecture," said researcher Joseph Buxbaum of the Icahn School of Medicine at Mount Sinai (ISMMS), in a news release." Although each exerts just a tiny effect individually, these common variations in the genetic code add up to substantial impact, taken together."

The findings of the Population-Based Autism Genetics and Environment Consortium study examined mutations that carry strong effects that favor the medical problem.

However, determining the exact cause of this behavioral health issue has been a topic of conversation for quite some time. Past studies have indicated that an interplay of genetics and other factors, including environmental issues dealt with during pregnancy, could also influence outcomes.

For the study, researchers compared a very large sample of about 3,000 people with autism with matched controls. They also carried out new statistical methods that allowed them to reliably sort out the heritability of the disorder.

In addition, researchers compared these results with a parallel study of 1.6 million Swedish families that took into account data from twins and cousins, as well as factored in things such as age of the father at birth and the parents' psychiatric history.

"This is a different kind of analysis than employed in previous studies," added Thomas Lehner, Ph.D., chief of NIMH's Genomics Research Branch. "Data from genome-wide association studies was used to identify a genetic model instead of focusing just on pinpointing genetic risk factors. The researchers were able to pick from all of the cases of illness within a population-based registry."

"Within a given family, the mutations could be a critical determinant that leads to the manifestation of ASD in a particular family member," concluded Buxbaum. "The family may have common variation that puts it at risk, but if there is also a de novo [spontaneous} mutation on top of that, it could push an individual over the edge. So for many families, the interplay between common and spontaneous genetic factors could be the underlying genetic architecture of the disorder."