Secondhand-smoke exposure linked to youths' mental health

A new study adds to a growing body of evidence that secondhand-smoke exposure is associated with negative mental health outcomes. Data for about 3,000 youngsters aged 8 to 15 years (2,901 nonsmokers and 141 current smokers) were drawn from the 2001 to 2004 National Health and Nutrition Examination Survey. Investigators used measurements of participants' level of serum cotinine, a metabolite of nicotine, to assess secondhand-smoke exposure among nonsmokers.

Among nonsmoking participants, serum cotinine level was positively associated with symptoms of major depressive disorder (MDD), generalized anxiety disorder (GAD), attention-deficit/hyperactivity disorder (ADHD), and conduct disorder, using criteria of the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV). The associations remained after adjustment for survey design, age, sex, race/ethnicity, and other factors. Serum cotinine level was most strongly associated with ADHD symptoms and was unassociated with symptoms of panic disorder.

The association between serum cotinine level and DSM-IV symptoms differed between girls and boys, however. Among male participants, the level was significantly associated with symptoms of MDD, GAD, ADHD, and conduct disorder. Among female participants, this association was significant only with symptoms of GAD and ADHD.

Commentary

This study is one of 2 published simultaneously in Archives of Pediatricsand Adolescent Medicine that demonstrated a link between smoke exposure, as measured by cotinine, and mental health in children. In this study, the association held with adjustment for a variety of factors, including prenatal smoke exposure and poverty, but there was no direct measure of parental mental health or stress. It may be that factors that cause family members to smoke have a direct effect on the mental well-being of the children. Nonetheless, I would still consider adding childhood mental illness to the list of complications of environmental smoke exposure.
-Michael Burke, MD