Secondhand Smoke Linked to Learning Disabilities, ADHD in Kids

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Kids who grow up among smokers are more likely than kids in smoke-free homes to suffer from a number of neurobehavioral disorders, including attention deficit hyperactivity disorder (ADHD), learning disabilities and conduct disorders.

That’s the finding from a new study published online this week in the medical journal Pediatrics.

Researchers from the Tobacco Free Research Institute in Dublin, Ireland, and from the Harvard School of Public Health reviewed data on more than 55,000 U.S. children under the age of 12. (The kids’ parents were interviewed as part of the 2007 National Survey on Children’s Health.) Of all the kids who grew up in smoke-free homes, 8.6% of them — or about one in 12 — had been diagnosed with at least one neurobehavioral condition. But among kids who lived with a smoker, more than twice as many — 20.4%, or one in five — had been diagnosed.

The study authors warn that that their findings so far are “associational and not necessarily causal,” which means that it cannot be known for sure whether secondhand smoke truly causes ADHD, learning disabilities and conduct disorders, or whether there’s something else that makes kids of smokers more likely to develop neurobehavioral disorders.

However, the researchers attempted to adjust statistically for other factors they thought might explain the correlation: things like the child’s sex, race, and age, as well as the poverty status of the household, the mother’s education, whether both parents lived at home, and whether the child was born with low birth weight.

If the relationship between secondhand smoke and neurobehavioral disorders were causal, the researchers calculate that would mean that some 274,100 excess cases of these disorders could have been prevented nationwide if children had not been exposed to secondhand smoke in their homes. Roughly 4.8 million American children under 12 live with smokers.

To date, the causes of ADHD are still poorly understood, and so are the causes of learning disabilities and conduct disorders. Overall, boys seem to be at higher risk than girls. It is not known how secondhand smoke could affect a child’s risk.

In slightly better news, a separate study appearing in Pediatrics finds that some kids who are exposed to cigarettes early on may be less likely to smoke later. For the study, researchers at the Washington University School of Medicine surveyed 165 children aged 8 to 13 about their attitudes toward cigarette smoke in the home; all the children lived with at least one adult smoker.

The researchers polled the children four times over the course of a year to try to gauge their ”smoking susceptibility.” Kids who had strong negative feelings about secondhand smoke were 78% less likely to try smoking than kids whose reactions were more neutral.

”We found that kids who reported that secondhand smoke exposure is ‘unpleasant’ or ‘gross’ were less likely to be susceptible to smoking,” study author Christina Lessov-Schlaggar told WebMD.