University of Southern California researchers published a first-of-its-kind study demonstrating a specific interaction between a well-known genetic risk factor and an environmental factor.
Looking at more than 400 children between the ages of 2 and 5, researchers also considered genetics and air-pollution exposure factors like local traffic-related pollution, how close mothers and children have lived to busy roadways, and regional air-quality reports.
They found that the MET gene variant, which is very common in the general population, is even more prevalent in individuals with autism. About 60 percent of children with autism have this genetic risk variant. "It's not a gene mutation; instead, it is a genetic risk variant that is associated with autism," explains Dan Campbell, PhD, assistant professor of psychiatry and the behavioral sciences, and Heather Volk, PhD, MPH, assistant professor of research in preventive medicine and pediatrics, both researchers at the Keck School of Medicine of University of Southern California.
Children with that gene variant who also experienced high air-pollution levels were even more likely to be diagnosed with autism spectrum disorder. The types of air pollution that seemed most likely to trigger autism in susceptible children include air pollution particles less than 10 microns in diameter and nitrogen dioxide, both of which increase the risk of autism threefold in kids with the risk genetic variant.
The researchers stress that their findings need to be replicated in a larger study before new health policies are developed.
For more ways the environment could be triggering autism and other developmental problems in children, read 10 Suspect Causes of Autism.