Smoking and common mental disorders: A population-based survey in Santiago, Chile

Smoking and common mental disorders (CMD), anxiety and depression, tend to co-exist and are important public health challenges for countries at all levels of development. The two largest U.S. psychiatric surveys detected clear associations between smoking and psychiatric disorders. In the Epidemiologic Catchment Area study (ECA) major depression was more common among smokers (6.6%) than non-smokers (2.9%). In the National Co-morbidity Survey (NCS), smoking rates for people with past-month mental illness were almost double the rates among those with no mental illness (41% vs. 23%). European cross-sectional studies have reported similar findings.

As for the temporal relationship between smoking and CMD, findings from prospective longitudinal studies are less consistent. For instance some studies report that CMD increases the risk of smoking whilst others find that there is no association between previous smoking and subsequent depression.

We identified only one other Latin American community survey reporting on the association between smoking and CMD. A Mexican cross-sectional study found that women smokers, regardless of the number of cigarettes smoked, were twice as likely to suffer depressive symptoms than never smokers but for men this association was only present for those smoking twenty or more cigarettes. However no statistical test for this interaction was reported. We found no prospective longitudinal studies investigating the association between CMD and smoking in Latin America.

Several studies conducted in the western world show that CMD and smoking are also commonly associated with an increased risk of other health-damaging behaviours, such as alcohol abuse or the use of illicit drugs. We found only one population-based study that investigated the co-morbidity of substance disorders and lifetime psychiatric diagnoses in Latin America but this study did not report on smoking. A few other Latin American studies have investigated associations between smoking, drinking and common mental disorders. For instance a Mexican cross-sectional survey of schools found associations between smoking, alcohol, use of illegal drugs, and depressive symptoms.

Studies suggest that Chile has the second highest prevalence of smoking among adults and the first among children and adolescents in Latin America whilst CMD are also highly prevalent. These are two of the most important public health problems facing this country and also other emerging economies. In this paper we expand on a previous report of an association between smoking and CMD using a wide range of better-defined variables and testing new hypotheses using different analytical techniques.

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Social Psychiatry and Psychiatric Epidemiology