American Journal of Epidemiology Advance Access originally published online on September 4, 2006
American Journal of Epidemiology 2006 164(9):918-919; doi:10.1093/aje/kwj306
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Letter to the Editor |
RE: "CIGARETTE SMOKING AND INCIDENCE OF FIRST DEPRESSIVE EPISODE: AN 11-YEAR, POPULATION-BASED FOLLOW-UP STUDY"
US Department of Health and Human Services, Centers for Medicare & Medicaid Services, 601 East 12th Street, Room 235, Kansas City, MO 64106
(e-mail: kazim.sheikh{at}cms.hhs.gov)
Klungsøyr et al. (1
) reported the results of a prospective study of the relation between cigarette smoking and depression among 2,727 adults selected from the participants of a Norwegian survey conducted in 1989–1991. The investigators reinterviewed 1,190 of these subjects soon after the survey and 11 years later. They found a fairly strong association between smoking and subsequent depression and a weak association between depression and subsequently initiated smoking (1).
The authors reported that six (1.3 percent) smokers had developed depression after they quit smoking during the 11-year follow-up period and that exclusion of data on these six subjects "had a negligible effect on the risk ratios" (1, p. 428). However, the number of smokers who quit smoking during follow-up and did not develop depression was not reported. Several years ago, Jorenby et al. estimated that each year, 40 percent of smokers in the United States try to quit smoking but only 6 percent succeed (2). Many smokers repeatedly attempt smoking cessation, and some eventually succeed. Most of the successful and unsuccessful quitters develop depression regardless of whether or not they receive nicotine replacement or bupropion (antidepressant) therapy (3–5). Pharmacotherapy is often initiated after the onset of depression symptoms. The risk of cessation-induced depression may or may not be associated with a past history of depression (6, 7).
If smoking causes or increases the risk of depression, as the authors found, smoking cessation should reduce the risk of depression. However, smoking cessation is known to provoke depression (8). If pharmacotherapy is initiated at the time of or just before smoking cessation, depression may be masked or aborted. The authors did not report data on pharmacotherapy in their study population.
At the community level, depression is underdiagnosed and underreported, and many affected persons are unaware of their depression (9). Klungsøyr et al.'s study interviews could have missed smoking cessation in the study population if it was not sustained. The study interviews may also have missed many episodes of depression, particularly those following attempted smoking cessation. It appears that the authors' definition of a "past smoker" was a subject who abstained from smoking for several years before the interview. Short-lived cessation was not included in the smoking classification.
The relation between smoking and depression is very complex. Tobacco smoke has antidepressant effects (10–12). That would explain the bidirectional association and cessation-induced depression. Treated or untreated smoking cessation is a significant confounding factor, and this study did not address it. Except for six study subjects, the analysis could not distinguish the depression events associated with smoking from those associated with smoking cessation.
ACKNOWLEDGMENTS
The views expressed in this letter do not represent the views and policies of the Centers for Medicare & Medicaid Services or the United States.
Conflict of interest: none declared.
References
- Klungsøyr O, Nygård JF, Sørensen T, et al. Cigarette smoking and incidence of first depressive episode: an 11-year, population-based follow-up study. Am J Epidemiol 2006;163:421–32.
[Abstract/Free Full Text] - Jorenby DE, Leischow SJ, Nides MA, et al. A controlled trial of sustained-release bupropion, a nicotine patch, or both for smoking cessation. N Engl J Med 1999;340:685–91.
[Abstract/Free Full Text] - Lerman C, Patterson F, Berrettini W. Treating tobacco dependence: state of the science and new directions. J Clin Oncol 2005;23:311–23.
[Abstract/Free Full Text] - Cox LS, Patten CA, Niaura RS, et al. Efficacy of bupropion for relapse prevention in smokers with and without a past history of major depression. J Gen Intern Med 2004;19:828–34.[CrossRef][ISI][Medline]
- Tsoh JY, Humfleet GL, Munoz RF, et al. Development of major depression after treatment for smoking cessation. Am J Psychiatry 2000;157:368–74.
[Abstract/Free Full Text] - Glassman AH, Covey LS, Stetner F, et al. Smoking cassation and the course of major depression: a follow-up study. Lancet 2001;357:1929–32.[CrossRef][ISI][Medline]
- Hitsman B, Borrelli B, McChargue DE, et al. History of depression and smoking cessation outcome: a meta-analysis. J Consult Clin Pschol 2003;71:657–63.
- Wilhelm K, Wedgwood L, Niven H, et al. Smoking cessation and depression: current knowledge and future. Drug Alcohol Rev 2006;25:97–107.[CrossRef][ISI][Medline]
- Whooley MA, Simon GE. Managing depression in medical outpatients. N Engl J Med 2000;343:1942–50.
[Free Full Text] - Hurt RD, Sachs DPL, Glover ED, et al. A comparison of sustained-release bupropion and placebo for smoking cessation. N Engl J Med 1997;337:1195–202.
[Abstract/Free Full Text] - Aubin HJ, Tilikete S, Barrucand D. Depression and smoking. Encephale 1996;22:17–22.[ISI][Medline]
- Balfour DJ, Ridley DL. The effects of nicotine on neural pathways implicated in depression: a factor in nicotine addiction? Pharmacol Biochem Behav 2000;66:79–85.[CrossRef][ISI][Medline]
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  O. Klungsoyr and J. F. Nygard TWO OF THE AUTHORS REPLY Am. J. Epidemiol., November 1, 2006; 164(9): 919 - 920. [Full Text] [PDF]
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