Department of Clinical and Biomedical Science: Barwon Health, The University of Melbourne, Victoria
Department of Clinical and Biomedical Science: Barwon Health, The University of Melbourne, Victoria, and Orygen Research Centre and Mental Health Research Institute, Australia
Correspondence: Julie A. Pasco, Epidemiology and Biostatistics Unit, Department of Clinical and Biomedical Sciences: Barwon Health, The University of Melbourne, PO Box 281, Geelong 3220, Australia. Email: juliep{at}barwonhealth.org.au
J.P., L.W., F.J. and M.B. have received research support from an unrestricted educational grant from Eli Lilly. Funding detailed in Acknowledgements.
Background
Smoking is disproportionately prevalent among people with psychiatric illness.
Aims
To investigate smoking as a risk factor for major depressive disorder.
Method
A population-based sample of women was studied using case–control and retrospective cohort study designs. Exposure to smoking was self-reported, and major depressive disorder diagnosed using the Structured Clinical Interview for DSM–IV–TR (SCID–I/NP).
Results
Among 165 people with major depressive disorder and 806 controls, smoking was associated with increased odds for major depressive disorder (age-adjusted odds ratio (OR)=1.46, 95% CI 1.03–2.07). Compared with non-smokers, odds for major depressive disorder more than doubled for heavy smokers (>20 cigarettes/day). Among 671 women with no history of major depressive disorder at baseline, 13 of 87 smokers and 38 of 584 non-smokers developed de novo major depressive disorder during a decade of follow-up. Smoking increased major depressive disorder risk by 93% (hazard ratio (HR)=1.93, 95% CI 1.02–3.69); this was not explained by physical activity or alcohol consumption.
Conclusions
Evidence from cross-sectional and longitudinal data suggests that smoking increases the risk of major depressive disorder in women.
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