Teens who smoke appear to be more likely to develop depressive symptoms than their nonsmoking peers, according to new research published in the October issue of Pediatrics. The study, "Depressive symptoms and cigarette smoking among teens," by Elizabeth Goodman, MD, and John Capitman, PhD, analyzed baseline and one-year follow-up data from the National Longitudinal Study of Adolescent Health to assess the relationship between cigarette smoking and depression among teens.

Researchers have typically viewed depression as increasing the likelihood of smoking behavior. But Goodman and Capitman's research has found the reverse: "Nondepressed teens who smoked in the prior month faced approximately a four times greater risk of developing depression than nonsmoking teens."

The researchers analyzed two samples of adolescents. The first sample of 8,704 nondepressed teens was studied to determine the effects of cigarette smoking on developing high depressive symptoms.

After one year, a majority of the sample's smoking behaviors did not change. However, more than one-third of those whose smoking behaviors did progress became moderate to heavy smokers, smoking at least a pack per week. About 6 percent of the baseline nondepressed teens developed high depressive symptoms at the follow-up.

The second sample of 6,947 depressed and nondepressed teens had not smoked cigarettes for 30 days prior to baseline; Goodman and Capitman looked for relationships between baseline depression and becoming a moderate to heavy smoker at follow-up.

In bivariate analyses, teens who smoked at baseline were more likely to develop depression, and depressed teens were more than twice as likely to become moderate to heavy smokers. Among teens who were not depressed at baseline, smokers were more than twice as likely to become depressed. Smoking behavior at one year was also highly associated with reporting depression. However, in logistic regression modeling, the bivariate relationship between depression and subsequent smoking was not significant.

Teens who smoked cigarettes in the 30 days before baseline were significantly more likely to develop depression in all models, even when controlling for sociodemographic factors. Goodman and Capitman explain that this finding "may indicate that depression led to the initial experimentation but that smoking is moderating the expression of the depressive symptoms."

Cigarette smoking was the single strongest predictor of developing high depressive symptoms, leading Goodman to say that "These data highlight the importance of providing anticipatory guidance regarding tobacco use to teen-agers and of encouraging smoking cessation among adolescents who smoke."

Among those who had never smoked at baseline, baseline depression was not associated with cigarette experimentation or smoking at follow-up. Neither was baseline depression associated with smoking at follow-up among those who had experimented at baseline.

"Because high depressive symptoms did not predict smoking behavior in these analyses, it is unlikely that the effect of current smoking on development of subsequent high depressive symptoms is simply a proxy for a past episode of depression," the authors reason.

And although depression would not be viewed as an antecedent of smoking in the study's framework, Goodman and Capitman say previous research might be explained in a different way that corresponds with their study. For example, nicotine may affect the central nervous system, causing the increased risk of depression.