As if there were not already enough evidence and reasons to avoid tobacco products, a recent study* revealed that cigarette smoking increased the chance of Major Depression Disorder (MDD) in women. Researchers compared cigarette use in 165 persons with MDD with over 800 persons without MDD in a case-controlled and retrospective design (uses accumulated data/records) that spanned 10 years. Exposure to smoking was associated with 1.5 greater odds of developing MDD. Heavy tobacco users fared even worse and were twice as likely to develop MDD as non-smokers. Long term, smokers’ risk of MDD doubled when tracked over a 10 year period. An understated finding was that physical activity served as a protective factor from onset of MDD. Note: All odds ratios above are approximate.
The central themes that emerged in this study repeat again and again in the research: increase your physical activity and limit tobacco exposure!
A few words on the study design. This research did not include a true experimental design, and thus one cannot say that “this causes that.” However, researchers will never use a true controlled design with tobacco products. Do you know why? Participants would have to sit in a lab smoking away for weeks, months, or years. Who would do this? Besides, this type of research design is ethically problematic since smoking increases risk for various forms of cancer, and researchers would intentionally expose participants to this known risk.
*Pasco, J., Williams, L., Jacka, F., Ng, F., Henry, M., Nicholson, G., Kotowicz, M., & Berk, M. (2008). Tobacco smoking as a risk factor for major depressive disorder: population-based study. The British Journal of Psychiatry, 193, 322-326.