The Cincinnati Children’s Hospital Medical Center issued the following
news release:

Exposure to lead, tobacco smoke raises risk of ADHD

Children exposed prenatally to tobacco smoke and during childhood to
lead face a particularly high risk for ADHD, according to research done
at Cincinnati Children’s Hospital Medical Center.

The study estimates that up to 35 percent of ADHD cases in children
between the ages of 8 and 15 could be reduced by eliminating both of
these environmental exposures. This could translate into up to 800,000

“Tobacco and lead exposure each have their own important adverse
effect,” says Tanya Froehlich, M.D., a physician in the Division of
Developmental and Behavioral Pediatrics at Cincinnati Children’s and the
study’s lead author. “But if children are exposed to both lead and
prenatal tobacco, the combined effect is synergistic.”

The study is to be published online Nov. 23 by Pediatrics.

“Although we tend to focus on ADHD treatment rather than prevention, our
study suggests that reducing exposures to environmental toxicants might
be an important way to lower rates of ADHD,” says Robert Kahn, MD, MPH.,
a physician and researcher at Cincinnati Children’s and the study’s
senior author.

The researchers found that children exposed prenatally to tobacco smoke
were 2.4 times more likely to have ADHD. Those with blood lead levels in
the top third had a 2.3 fold increased likelihood of ADHD, despite
levels well below the Centers for Disease Control action level of 10
micrograms per deciliter. Dr. Froehlich and her colleagues found the
risk of ADHD more than eight times higher for children exposed to both
tobacco and lead compared to unexposed children.

The study is based on data of 8 to 15 years olds gathered between 2001
and 2004 from the National Health and Nutrition Examination Survey
(NHANES) from the National Center for Health Statistics at the Centers
for Disease Control and Prevention. NHANES is a nationally
representative sample of the United State population, designed to
collect information about the health and diet of people in the U.S.

Prenatal tobacco exposure was measured by maternal reports of cigarette
use during pregnancy. Lead exposure was assessed using current blood
lead level. Some 8.7 percent of the 3,907 children in the study met
diagnostic criteria for ADHD. The diagnosis for ADHD was based on the
Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition,
considered the “gold standard” for defining specific mental health conditions.

The study was funded by grants from the National Institutes of Health
and the Academic Pediatrics Association, and a Robert Wood Johnson
Generalist Physician Faculty Scholars Award.