The study, conducted by researchers at Cincinnati Children's Hospital Medical Center, found a dose-response relationship between serum cotinine levels (a marker for secondhand smoke exposure) and behavioral and psychological problems, including acting out, having problems at school, and experiencing anxiety and depression.
Dr. Yolton found a relationship between cotinine levels and increases in acting out; increases in holding things in, often manifested by anxiety and depression; increases in behavior problems as rated by parents, and behavior and school problems as rated by teachers; and, decreases in the ability to adapt to behavior problems.
According to the press release issued to the media to publicize the results of this study: "'The greater the exposure to tobacco smoke, the greater the problems these children had,'" says Dr. Yolton. 'Behavior problems in children have increased from 7 to 18 percent over the last 20 years for reasons that are poorly understood. Exposure to environmental tobacco smoke is increasingly recognized as a risk factor for child behavior problems.'"
The study's lead author concluded that: "This study provides further incentive for states to set public health standards to protect children from exposure to environmental tobacco smoke."
The Rest of the Story
Let's not be hasty.
There are a number of reasons why children who are exposed to secondhand smoke would be expected to have more behavioral and psychological problems than children who are not exposed, and the exposure is not at the top of the list.
Children who are exposed to secondhand smoke represent a very different population than kids who are not exposed, and the factors that make these populations different are precisely those that would be expected to influence the childrens' behavior and psychological health.
For one thing, these kids' parents are more likely to be smokers. And there's a reason why their parents smoke. Perhaps the level of environmental stress and ways of dealing with life stress is different in smoking and non-smoking households. And perhaps those differences in life stress and lifestyle coping strategies has something to do both with the parents' decisions regarding smoking (and thus to secondhand smoke exposure) and with the childrens' own levels of life stress and their coping mechanisms.
These factors, which are likely related both to secondhand smoke exposure and to childrens' behavioral and psychological problems, are what we call potential confounders. Their presence can mean that the observed link between secondhand smoke exposure and behavioral problems in children is a spurious one, rather than a causal one.
And at this point in time, given the existing scientific literature, I think it is far too premature to conclude that secondhand smoke exposure causes behavioral and psychological problems in children and adolescents and that this is a reason why we should protect children from exposure to secondhand smoke.
In fact, the secondhand smoke exposure might actually be a red herring here that distracts our attention away from the real source of the problem.
Perhaps what is needed to remedy this particular problem is not reduced exposure to secondhand smoke, but interventions to help teach young children more effective mechanisms for coping with stressors in life, to help young kids learn to be able to share their problems and not to hold everything inside, and to improve social support systems in families, schools, and communities that can foster improved behavior and improved mental health.
There are other reasons why children should be protected from secondhand smoke (such as the risk that they could have a heart attack if exposed for 30 minutes or more). But at this point in time, concluding that secondhand smoke causes behavioral and psychological problems in kids is jumping the gun.