University of North Carolina at Chapel Hill issued the following announcement:

UNC study: Parenting can override effect of genes in how babies respond
to stress

Everyone gets stressed, even babies.

Now, it appears how infants respond to stress is linked to if they have
a particular form of a certain gene, according to a new study from the
University of North Carolina at Chapel Hill.

Just as significantly, researchers say they have also found that good
parenting – as early as within the first year of a child’s life – can
counter the effect the gene has in babies who initially do not respond
well to stressful situations.

“Infancy is an important time for developing behavioral and biological
processes,” said the study’s lead author, Cathi Propper, Ph.D., research
scientist at UNC’s Center for Developmental Science. “Although these
processes will continue to change over time, parenting can have
important positive effects even when children have inherited a genetic
vulnerability to problematic behaviors.”

The study findings appear in the September/October 2008 issue of the
journal Child Development.

Researchers looked at 142 infants over the first year of their lives,
when the children were 3, 6 and 12 months old. On each occasion, they
were placed in a stressful situation — being separated from their
mothers — and researchers measured the infants’ heart rates, looking
specifically at a type of cardiac response called vagal tone. Vagal tone
acts like a brake on the heart when the body is in a calm state, but
during challenging situations, the brake is withdrawn and the level of
vagal tone goes down, allowing heart rate to increase so the body can
actively deal with the challenge.

Researchers also collected DNA from the infants to see which form of a
dopamine receptor gene they carried. Previous studies have shown that
adolescents and adults with specific forms of this gene are more likely
to have problems such as aggression, substance abuse and other risky

When the babies were 6 months old, researchers also videotaped the
mothers and their infants playing together for 10 minutes, and assessed
whether the mothers’ behavior was high or low in sensitivity.

Propper said the study found both genes and parenting were important to
the development of how infants’ brains help regulate cardiac responses
to stress.

At 3 and 6 months old, infants with the form of the dopamine gene
associated with risky behaviors did not display a decrease in vagal tone
when stressed, while those with the non-risk version of the gene did. At
these early ages, it did not appear to matter whether mothers were
sensitive or not, Propper said.

However, by the time the infants were 12 months old, the pattern
changed. Infants with the risk form of the gene whose mothers were
highly sensitive now showed the expected cardiac response when under
stress – while those with the at-risk gene form who had insensitive
mothers did not.

Propper said the findings suggest that although genes play a role in the
development of physiological responses to stress, environmental
experiences – such as mothers’ sensitive care-giving behavior – can have
a strong influence, enough to change the effect that genes have on
physiology very early in life.

“Our findings provide further support for the notion that the
development of complex behavioral and physiological responses is not the
result of nature or nurture, but rather a combination of the two,”
Propper said. “They also illustrate the importance of parenting not just
for the development of children’s behavior, but for the underlying
physiological mechanisms that support this behavior.

“Infancy is an important time for developing behavioral and biological
processes. Although these processes will continue to change over time,
parenting can have important positive effects even when children have
inherited a genetic vulnerability to problematic behaviors,” Propper said.

Study co-authors from UNC are W. Roger Mills-Koonce, Ph.D., research
scientist with the Center for Developmental Science; Martha Cox, Ph.D.,
director of the center and psychology professor in the College of Arts
and Sciences; Carolyn Tucker Halpern, Ph.D., associate professor of
maternal and child health in the School of Public Health; and Ashley L.
Hill-Soderlund, a post-doctoral fellow at the center at the time of the
study who is now an assistant professor at St. Norbert College in De
Pere, Wis. Other co-authors are Mary Anna Carbone, Ph.D., from North
Carolina State University; Ginger A. Moore, Ph.D., from Pennsylvania
State University; and Susan D. Calkins, Ph.D., from UNC-Greensboro. The
study was funded by the National Science Foundation.