Stressed-out Americans tend to vent. They talk about their troubles, and call up their friends for validation. Most Koreans, on the other hand, would rather keep it to themselves.

According to a new study, that difference between European American and Korean customs is so powerful that it shapes the expression of biology: A genetic profile linked to empathy and sociability yields two very different behavioral outcomes, depending on the culture.

Other studies have described how the interaction of traumatic events and genes can influence a person’s risk for schizophrenia or other psychological disorders. But “environment” is more than disasters and childhood experience.

“We’re trying to broaden the notion of environment [away] from risk factors in your personal life,” said Heejung Kim, a social psychologist at the University of California-Santa Barbara. “We wanted to see … about a shared environment, and started to look at the role of culture.”

In the new study, published Aug. 16 in the Proceedings of the National Academy of Sciences, Kim's team looked at the relationship between culture and a gene called OXTR. The gene encodes a receptor for the hormone oxytocin, renowned for its ability to promote social bonding. OXTR comes in two versions, G and A.

In Western cultures, people with at least one G version of the gene tend to be more sensitive parents, less lonely, more empathic, and have lower rates of autism than people with the A version.

Kim’s team reasoned that, among European Americans, social G people would be more likely than A people to go to friends and family for emotional support during tough times. Kim’s survey of 140 European American adults, published online this week in Proceedings of the National Academy of Sciences, confirmed that prediction.

In Korea, though, even having the social G version of OXTR didn’t prompt people to talk about their feelings. In fact, a survey of 134 Koreans hinted at just the opposite: Stressed Koreans with the G version were the most reluctant to seek social support.

Kim thinks that’s because the more social and empathic G types are closely attuned to their cultural norms — which, in Korea, dictate that one doesn’t share one’s problems.

“Asian cultures are collectivistic cultures. You have to care what people think of you a lot more,” Kim said. “So by seeking emotional support you’re disclosing your problems to … others. You might make that person get worried. You might have to worry about embarrassing yourself to other people.”

That’s still speculation – but it might explain how the same version of the same gene can give rise to venting in one culture, but are bottled in another.

Korean Americans had the same patterns of expression as European Americans, reducing the possibility that other unstudied Korean genes are causing the difference.

“This [study] is really breaking new ground,” said Joan Chiao, a cultural neuroscientist at Northwestern University who studies how culture affects human behavior. It’s one of the first to show that cultural norms themselves are environmental factors that interact with genes, said. That brings together two branches of science that have a long history of separation.

“We’re making really important concrete steps toward bridging [gaps between] culture and biological sciences,” Chiao says. “That’s going to ultimately pay off in our understanding of physical and mental health factors that we all care about.”

Photo: Jim Merithew/Wired.com

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Citation: "Gene-culture interaction: Effects of culture, distress, and oxytocin receptor polymorphism on emotional support seeking." By Heejung S. Kim, David K. Sherman, Joni Y. Sasaki, Jun Xu, Thai Q. Chu, Chorong Ryu, Eunkook M. Suh, Kelsey Graham, Shelley E. Taylor. Proceedings of the National Academy of Sciences, Vol. 107. No. 34, August 17, 2010.