a1 Department of Psychiatry, University of California, San Francisco, CA, USA
a2 Division of General Internal Medicine, Department of Medicine and Medical Effectiveness Research Center for Diverse Populations, University of California, San Francisco, CA, USA
Background Limited evidence has suggested that quitting smoking increases the incidence of major depressive episodes (MDEs), particularly for smokers with a history of depression. Further evidence for this increase would have important implications for guiding smoking cessation.
Method Spanish- and English-speaking smokers without a current MDE (n=3056) from an international, online smoking cessation trial were assessed for abstinence 1 month after their initial quit date and followed for a total of 12 months. Incidence of screened MDE was examined as a function of abstinence and depression history.
Results Continued smoking, not abstinence, predicted MDE screened at 1 month [smoking 11.5% v. abstinence 7.8%, odds ratio (OR) 1.36, 95% confidence interval (CI) 1.04–1.78, p=0.02] but not afterwards (smoking 11.1% v. abstinence 9.8%, OR 1.05, 95% CI 0.77–1.45, p=0.74). Depression history predicted MDE screened at 1 month (history 17.1% v. no history 8.6%, OR 1.71, 95% CI 1.29–2.27, p<0.001) and afterwards (history 21.7% v. no history 8.3%, OR 3.87, 95% CI 2.25–6.65, p<0.001), although the interaction between history and abstinence did not.
Conclusions Quitting smoking was not associated with increased MDE, even for smokers with a history of depression, although a history of depression was. Instead, not quitting was associated with increased MDE shortly following a quit attempt. Results from this online, large, international sample of smokers converge with similar findings from smaller, clinic-based samples, suggesting that in general, quitting smoking does not increase the incidence of MDEs.
(Received August 18 2008)
(Revised May 14 2009)
(Accepted May 29 2009)
(Online publication July 23 2009)
c1 Address for correspondence: R. F. Muñoz, University of California, San Francisco, Department of Psychiatry at San Francisco General Hospital, 1001 Potrero Avenue, Suite 7M, San Francisco, CA 94110, USA. (Email: firstname.lastname@example.org)