Quitting smoking does not increase the risk of major depressive episodes among users of Internet smoking cessation interventions

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 I month (history 17.1 % v. no history 8.6%, OR 1.71, 95% Cl 1.29-2.27, p<0.001) and afterwards (history 21.7% v. no history 8.3%, OR 3.87, 95% Cl 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.