Study found one more than doubled chances, while both increased risk eightfold
MONDAY, Nov. 23 (HealthDay News) -- Children whose mothers smoked during pregnancy or who were exposed to lead have more than double the risk of having attention-deficit hyperactivity disorder (ADHD) as other children, new research shows.
And with exposure to both cigarettes and lead, the chances of having ADHD soared. Children whose mothers smoked during pregnancy and whose blood showed signs of lead exposure had eight times the risk of having ADHD.
"When you have both exposures, there is a synergistic effect," said study author Dr. Tanya Froehlich, a developmental and behavioral pediatric specialist and an assistant professor of pediatrics at Cincinnati Children's Hospital Medical Center.
The researchers concluded that about 38 percent of ADHD cases among children aged 8 to 15 in the United States may be caused by prenatal exposure to tobacco smoke, while 25 percent of ADHD cases are due to lead exposure, according to the study in the Nov. 23 online issue of Pediatrics.
Froehlich and her colleagues used data on 2,588 children aged 8 to 15 from around the nation who took part in the 2001-2004 National Health and Nutrition Examination Survey. Tobacco exposure was assessed by asking mothers if they smoked during pregnancy, while lead concentrations were measured by a blood test.
About 8.7 percent of children met the criteria for ADHD, which is marked by inattentiveness, difficulty focusing, impulsivity and hyperactivity, according to the study. The ADHD group included 16.8 percent of children whose mothers smoked during pregnancy, compared to 6.6 percent of children whose mothers did not smoke.
Lead exposure was divided into three groups: low, medium and high. About 5.2 percent of children who had the lowest lead blood levels had ADHD. About 9.1 percent of children in the middle range had ADHD, whil
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