"We found that children who are exposed to secondhand smoke in the home have a 50% increased odds of having two or three of these common neurobehavioral disorders," says researcher Hillel Alpert, ScM, at the Harvard School of Public Health.
The study is published in the journal Pediatrics.
In the same issue, another study looked at how children's reaction to secondhand smoke may predict whether they will smoke.
Secondhand Smoke and Learning and Behavior Problems
For years, doctors have known that secondhand smoke can take a health toll on children. It increases the risk of respiratory problems, ear ailments, and other problems, Alpert says.
His team wanted to look at learning and behavior problems. They evaluated data from the 2007 National Survey of Children's Health. The telephone survey included more than 91,000 children. For this study, the researchers focused in on the 55,358 children younger than 12.
Of these 55,358 children, 6% were exposed to secondhand smoke in the home in 2007.
Parents reported if their child had been diagnosed or treated for ADHD, behavioral and conduct disorders, or learning disabilities.
''We analyzed the relationship between parents who reported smoking in the home as opposed to those not smoking in the home and these disorders," Alpert says.
He calls the 50% increased risk substantial. The findings do not prove cause and effect, he says, only a link.
Exactly how the smoke exposure is linked with the disorders is not known, Alpert says.
The study was supported by the Flight Attendants Medical Research Institute. Researchers included Zubair Kabir, MD, PhD, of the Tobacco Free Research Institute in Dublin.
Secondhand Smoke and Susceptibility Study
In a second study, Christina Lessov-Schlaggar, PHD, a research assistant professor at the Washington University School of Medicine, polled 165 children, aged 8 to 13, about their reaction to secondhand smoke in the home.