Volume 3, Issue 3
Secondhand Smoke Exposure and Mental Health
By Frank Charlie Bandiera, MPH
My name is Frank Bandiera, and I am a fourth year doctoral epidemiology student at the University of Miami. I was awarded an individual pre-doctoral grant from the National Institute of Mental Health to study the biological and behavioral mechanisms underlying chronic physical conditions, such as asthma, and poor mental health outcomes, such as anxiety and depression. I am interested in integrating the biological and behavioral sciences with public health and have received advanced training in structural equation modeling, behavioral medicine, psychoneuroimmunology, neurosciences, and genetics. I am part of several research groups but will focus on a paper in which I was awarded the 2010 National Award of Excellence by a Student by the National Hispanic Science Network on Drug Abuse. In the last two years I have published six articles on the health outcomes of secondhand smoke exposure (SHS) (i.e., depression, disturbed sleep, and hearing loss). The paper which was awarded the national award was published in 2010 in Psychosomatic Medicine entitled “Secondhand smoke exposure and depressive symptoms.” This article was the first to find an association between SHS and depression; and subsequent studies published later have found similar findings in journals such as Archives of General Psychiatry and Archives of Pediatrics and Adolescent Medicine.
It is well established that cigarette smokers are at greater risk for poor mental health. However, the exact nature of this association is not clear. It is possible that smokers smoke to “self-medicate” or it is possible that cigarette smoking precedes and causes poor mental health; alternatively, a shared predisposition, such as family history, may explain this association.
In the paper I published I used the 2005-2006 National Health and Nutrition Examination Surveys (NHANES), which is a cross-sectional nationwide probabilistic sample of noninstitutionalized individuals. Depression was measured by a 9-item Patient Health Questionnaire and SHS by serum cotinine among non-smokers, which is the primary metabolite of nicotine. I found that SHS was positively associated with symptoms of depression among non-smoking adults, and a recent prospective analysis of a large cohort of adults conducted over six years by Hamer et al. (2010) suggests that SHS may predict the onset of anxiety and depression. Other follow-up studies have also suggests that SHS is associated with symptoms of anxiety, depression, attention deficit, and hyperactivity in children and adolescents.
Despite evidence of an association, the mechanism by which SHS may promote or exacerbate poor mental health is unclear. SHS may be a proxy for stressful living conditions, and stress has been associated with poor mental health. There are also hypotheses that suggest a link between smoking and poor mental health through the influence of nicotine and dopamine pathways. Regardless of the potential mechanisms, results from previous studies have important public health implications. Currently, only 26 states in the US have banned smoking in all public places, such as bars and restaurants, despite evidence that comprehensive public smoking bans have led to reductions in the incidence of cardiovascular and respiratory conditions. Similar improvements in population-level mental health may be possible.
Future studies should further investigate the etiology and biological and behavioral mechanisms to further establish causality. Perhaps a shared family history may explain the association. For example, children exposed to SHS may likely have mothers who are smokers, and perhaps they have poor mental health not because of SHS but because they have a familial predisposition to have poor mental health. On the other hand, it is possible for SHS to have a direct effect on neurobiological mechanisms; thus, smaller studies should be conducted. Behavioral confounders, such as psychological stress and a dysfunctional family climate can also be taken into consideration. Unfortunately, smoking has not been banned in all states in the US. However, in states in the US and countries where smoking has been banned, rates of mental disorders can be compared before and after the bans have been implemented. In conclusion, the finding that SHS is associated with poor mental health is still in its infancy and warrants more research to inform scientists, policymakers, and the public-at-large about another potential harm caused by SHS.