Register for Combination of Genes and Prenatal Exposure to Smoking Increases Teens’ Risk
of Disruptive Behavior
NIDA Study Shows Different Gene Variants Influence this Risk for Girls and Boys.
Wednesday, March 4, 2009
Kim DiFonzo, NIDA
301-443-6245
A study funded by the National Institute on Drug Abuse, a component of the
National Institutes of Health, shows that prenatal exposure to smoking combined
with a specific genetic variant places children at greatest risk for behavioral
problems. Many studies have established that there is an increased risk of
aggressive behavior in children exposed to cigarette smoke before birth, a
significant problem given that many women still smoke during pregnancies.
According to the National Survey on Drug Use and Health, in 2006-2007 slightly
more than 16 percent of pregnant women aged 15-44 (426,000) were current
cigarette smokers.
A team of researchers led by the Institute for Juvenile Research, University of
Illinois at Chicago, identified a long-lasting influence on behavior of the
monoamine oxidase A (MAOA) gene variant following tobacco exposure before birth.
MAOA is an enzyme which regulates key neurotransmitters[*], or chemical
messengers in the brain. Strikingly, the genetic variant that confers this
increased risk differs between boys and girls.
"These findings illuminate how the interaction between genes and the environment
can mold behavioral patterns very early in development," said NIDA Director Dr.
Nora Volkow. "This research provides a foundation for studies of the impact of
these interactions on brain development during pregnancy."
The researchers studied 176 non-Hispanic white youth, whose average age was 15,
and their biologic mothers. In contrast with previous studies of prenatal
smoking that have measured exposure based on the mother’s recollection of past
smoking, this study obtained accurate measurements of smoking behaviors during
the actual pregnancy.
In boys, with the low-activity MAOA (MAOA-L) gene variant, exposure to prenatal
smoking was associated with increased disruptive social interactions, including
aggressive behaviors and serious rule-violating. "Low activity" means that the
gene produces less of its product, the enzyme monamine oxidase A. In contrast,
exposure to prenatal smoking was associated with increased disruptive behavior
in girls who had the high-activity MAOA (MAOA-H) variant. For both boys and
girls, the more their mothers had smoked during pregnancy, the higher the risk
of disruptive behavior.
Additionally, on computerized tasks, girls with both the MAOA-H variant and
prenatal exposure to smoking had a greater tendency to perceive anger in a range
of facial expressions, a tendency that researchers term "hostile attribution
bias." This effect was not seen among boys.
"The tendency to over-perceive anger suggests the possibility that the
combination of prenatal tobacco exposure and the MAOA risk variant affects the
brain’s processing of emotional cues," said the study’s principal investigator,
Dr. Lauren S. Wakschlag, associate professor of psychiatry at the Institute for
Juvenile Research, University of Illinois at Chicago. "Individuals with a
greater tendency to perceive hostility in others are more likely to respond
aggressively. These findings provide us with clues to the possible mechanism by
which prenatal exposure may exert its effects on brain and behavior. Clearly,
close attention to sex differences in these patterns will be critical for future
studies."
Dr. Wakschlag led the study in collaboration with colleagues from the Institute
for Juvenile Research as well as researchers from the National Institute of
Mental Health (which is also a component of the National Institutes of Health);
the University of Chicago; Harvard University Medical School; and the University
of York, England.
The National Institute on Drug Abuse is a component of the National Institutes
of Health, U.S. Department of Health and Human Services. NIDA supports most of
the world’s research on the health aspects of drug abuse and addiction. The
Institute carries out a large variety of programs to inform policy and improve
practice. Fact sheets on the health effects of drugs of abuse and information on
NIDA research and other activities can be found on the NIDA home page at
www.drugabuse.gov
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drugpubs@nida.nih.gov
The National Institutes of Health (NIH) — The Nation's Medical Research Agency —
includes 27 Institutes and Centers and is a component of the U.S. Department of
Health and Human Services. It is the primary federal agency for conducting and
supporting basic, clinical and translational medical research, and it
investigates the causes, treatments, and cures for both common and rare
diseases. For more information about NIH and its programs, visit
www.nih.gov
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* i.e., dopamine, epinephrine, norepinephrine, serotonin
