Genes Drive Kids' Changing Fears
Child Fears Change Over Years as Genes Shift Gears
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
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
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.