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Genes Drive Kids' Changing Fears

Child Fears Change Over Years as Genes Shift Gears
By
WebMD Health News
Reviewed by Louise Chang, MD

April 7, 2008 -- Scaredy-cat genes make scary things more frightening to some kids than to others. But these fears -- and the genes that drive them -- change as kids age, a twin study shows.

The idea that genes drive fear isn't new. Small children tend to be naturally afraid of things, such as snakes, that were dangerous to our ancestors. But they aren't afraid of many very dangerous things, such as guns or electrical outlets, that our ancestors never saw.

Kenneth S. Kendler, MD, professor of both psychiatry and human genetics at Virginia Commonwealth University, Richmond, led a team that tested this theory using data from a long-term study that followed pairs of Swedish twins from age 8 to adulthood. Data was collected four times: at ages 8-9, 13-14, 16-17, and 19-20.

The twins, and their parents, were asked about how frightened the children were -- ranging from not at all scared to absolutely terrified -- of a long list of items including fear of snakes, fear of spiders, fear of heights, fear of flying, and other things often seen as scary.

"Our question was, how important are genetic factors in the fears of these children?" Kendler tells WebMD. "The answer is, pretty important. I was not completely surprised by this -- but I didn't expect the results to be as dramatic as they are."

Child's Development, Environment Affect Fear Genes

What surprised the researchers was that though genetic factors strongly influenced children's fears, these factors changed over time.

"One model of genetic influence is you get a hunk of genes from mom and dad and they make you a more fearful person or a less fearful person. That is not what we saw at all," Kendler says. "We saw something much more dynamic. When you are a 7- or 8-year-old, the genes acting on your fears are different than those that act on your fears when you are going through puberty. And they continue to differ as you go into young adulthood."

This makes sense in terms of evolution, Kendler says.

"Let's go back 500,000 years ago: What are the sorts of things a 7- or 8-year-old might be afraid of in their environment? It might be a snake that might bite them. It might be the dark, because if you are 7 and lost and it is dark and can't get back to your parents you are going to be meat for the cheetahs or hyenas," he says. "But by the time you are 20 years old the kinds of risks you are going to be afraid of are different. It might be social factors -- such as other people who are going to brain you if you are after their girlfriend."

Kendler believes that what is true of normal fears is also true of the more intense, disabling fears known as phobias. That is, he feels the genetic influence on these disorders changes through childhood.

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