Research suggests that environmental factors, such as a parent’s age or the mother’s infection during pregnancy, can contribute to autism risk. But identifying those factors has been incredibly challenging. Studies often have conflicting results — one might find that exposure to air pollution increases risk for autism, while another finds no such link.
One reason for this discrepancy could be that environmental and genetic risk factors can interact. In other words, an environmental variable, such as air pollution, might increase autism risk only in people who are genetically susceptible. A classic example of this type of interaction is phenylketonuria, a metabolic condition linked to intellectual disability. Children with the disorder are at risk of brain damage, but only if they eat a high-protein diet. An environmental factor (diet) and a genetic factor (a faulty metabolism gene) interact to cause phenylketonuria. Early screening and a special diet drastically reduce symptoms. (All infants in the United States are tested for the disorder.)
Heather Volk and collaborators at Johns Hopkins University in Baltimore aim to explore whether this type of interaction also applies to autism. “We think that autism can’t be explained only by genes or environmental factors alone,” Volk says. “It’s likely a combination of these two things working together.” She cautions that autism will likely prove much harder to understand than phenylketonuria because multiple genetic and environmental factors probably contribute to risk.
The project, called GEARS (Genes and Environment Autism Research Study), will survey parents about different environmental exposures. These include where the mother lived during pregnancy (a proxy for air pollution), whether she took prenatal vitamins, and whether she had infections or was hospitalized during pregnancy. The researchers will then look for links between environmental and genetic data. They hope to identify new risk factors that become apparent when both environmental and genetic contributions are taken into account.
Studies looking at gene-environment interactions require huge numbers of people. That’s where SPARK comes in — one of SPARK’s goals is to connect scientists and people who want to participate in research. Volk said she was excited to learn about the SPARK project because of its large size and the fact that participants undergo genetic testing. SPARK members who qualify for this and other studies will receive emails inviting them to participate.
Volk cautions that it’s too early to give parents advice on how to reduce risk. “Until we know more about environmental risk factors and the times they are important, it’s hard to think about remediation or avoidance,” she says.