Examination of the temporal relationship between smoking and major depressive disorder among low-income women in public primary care clinics

Purpose. To determine the prevalence of major depressive disorder (MDD) by smoking status, and the temporal relationship between smoking and MDD, and explore other smoking-related variables that may be associated with MDD. Design. Cross-sectional study. Setting. Public primary care clinics. Subjects. Researchers studied 338 women (76% African-Americans) who were randomly selected while attending appointments in two public primary care clinics. Measures. Data pertaining to smoking-related variables and MDD diagnosis were obtained using the Diagnostic Interview Schedule for the Diagnostic Statistical Manual of Mental Disorders IV (DSM-IV). Results. The prevalence of a lifetime history of MDD was significantly higher for current smokers (56.6%) than among former smokers (37.5%) or never-smokers (30.3%; p < .001). Most ever-smokers (81.3%) began smoking and were nicotine-dependent (63.6%) prior to their first episode of MDD. Using logistic regression, after controlling for demographic and smoking-related variables, age of smoking onset was the strongest variable associated with MDD among ever-smokers. Specifically, the odds of having an MDD decreased by 8.2% for each year delay, in smoking initiation. Conclusion. These results suggest that smoking initiation precedes MDD and that smoking is associated with a high prevalence of MDD among low-income women attending primary care clinics. Further, the younger women start smoking the more likely they are to have MDD.