Aims: To determine whether signs of current depression predict attempts to quit smoking, and short-term abstinence among those who try, and to test moderating effects of gender and cessation support (pharmacological and behavioural). Design: Prospective cohort with approximately annual waves. Among smokers at one wave we assessed outcomes at the next wave using mixed-effects logistic regressions. Setting: Waves 5–8 of the Four Country International Tobacco Control Study: a quasi-experimental cohort study of smokers from Canada, USA, UK and Australia. Participants: A total of 6811 tobacco smokers who participated in telephone surveys. Measurements: Three-level depression index: (1) neither low positive affect (LPA) nor negative affect (NA) in the last 4 weeks; (2) LPA and/or NA but not diagnosed with depression in the last 12 months; and (3) diagnosed with depression. Outcomes were quit attempts and 1-month abstinence among attempters. Findings: Depression positively predicted quit attempts, but not after controlling for quitting history and motivational variables. Controlling for all covariates, depression consistently negatively predicted abstinence. Cessation support did not moderate this effect. There was a significant interaction with gender for quit attempts (P = 0.018) and abstinence (P = 0.049) after controlling for demographics, but not after all covariates. Depression did not predict abstinence among men. Among women, depressive symptoms [odds ratio (OR) = 0.63, 95% confidence interval (CI) = 0.49–0.81] and diagnosis (OR = 0.46, 95% CI = 0.34–0.63) negatively predicted abstinence. Conclusions: Smokers with depressive symptoms or diagnosis make more quit attempts than their non-depressed counterparts, which may be explained by higher motivation to quit, but they are also more likely to relapse in the first month. These findings are stronger in women than men.
- Adult Australia Canada Cohort Studies Depression/*psychology Depressive Disorder/*psychology Female Humans Male Middle Aged *Motivation Prospective Studies Recurrence Sex Factors Smoking/*psychology/therapy Smoking Cessation/*psychology Tobacco Smoking/therapy United Kingdom United States *Cessation support *Depression *depressive symptoms *gender *relapse *smoking cessation