Nearly 60 percent of the risk of developing autism can be linked to gene variants common in most of the population and occurring in people who do not have the disorder, according to an international study. The study, published in the July 20 issue of Nature Genetics, concluded that heritability outweighed other risk factors, including environmental, as a contributor to autism.
“From this study, we can see that genetics plays a major role in the development of autism compared to environmental factors, making autism more like height and weight than we thought – many small risk factors add up, each pushing a person further out on the spectrum,” co-lead investigator Kathryn Roeder, PhD, professor of statistics and computational biology at Carnegie Mellon University (CMU), Pittsburgh, said in a CMU news release.
Autism has been attributed to an interplay of genetic and other factors, including environmental influences. However, medical professionals and investigators have not been able to agree on their relative contributions to the cause of the disorder or its genetic outline. With this study, the research team from the Population-Based Autism Genetics and Environment Study (PAGES) Consortium concludes that an understanding of autism genetics is beginning to emerge.
The PAGES investigators used data from Sweden’s universal health registry to compare roughly 3,000 subjects, including those with autism and a control group. The research team also used new statistical methods that allowed them to more reliably determine inherited factors of the disorder. The new methods helped them to pinpoint such genetic risk factors as deletions and duplications in genetic material and spontaneous mutations, providing a better understanding of autism’s genetic architecture.
The study findings showed that about 52 percent of autism can be linked to common genes and rarely inherited variations. Spontaneous mutations contributed just 2.6 percent of the total risk for the disorder.
The study’s first author, Joseph D. Buxbaum, PhD, director of the Seaver Autism Center for Research and Treatment, and professor of psychiatry, neuroscience and genetics and genomic sciences at the Ichan School of Medicine at Mount Sinai in New York City, noted that inherited common variants comprise the bulk of the risk that sets up susceptibility to autism.
But that’s only piece of the puzzle. Even though rare spontaneous mutations accounted for a small percentage of risk, “within a given family, the mutations could be a critical determinant that leads to the manifestation of autism spectrum disorder in a particular family member,” Buxbaum said in a Mount Sinai Hospital news release.
“If the family has a common variation that puts it at risk, an added [spontaneous] mutation could push an individual over the edge and result in that person developing the disorder,” explained Buxbaum.