Changes in prevalence of depression and anxiety following smoking cessation: results from an international cohort study (ATTEMPT).

BACKGROUND: Smoking cessation improves physical health but it has been suggested that in vulnerable individuals it may worsen mental health. This study aimed to identify the short- and longer-term effects of stopping smoking on depression and anxiety in the general population and in those with a history of these disorders.
METHOD: Sociodemographic and smoking characteristics, and mental and physical health were assessed using established measures in the ATTEMPT cohort, an international longitudinal study of smokers (n = 3645). Smokers who had stopped for at least 3 months or less than 3 months at the 12-month follow-up were compared with current smokers (n = 1640).
RESULTS: At follow-up, 9.7% [95% confidence interval (CI) 8.3-11.2] of smokers had stopped for less than 3 months and 7.5% (95% CI 6.3-8.9) for at least 3 months. Compared with current smokers, prevalence of depression prescriptions obtained in the last 2 weeks was lower for those who had stopped for less than 3 months [odds ratio (OR) 0.37, 95% CI 0.14-0.96] or at least 3 months (OR 0.25, 95% CI 0.06-0.94) after adjusting for baseline prescription levels and confounding variables. Adjusted prevalence of recent depression symptoms was also lower for ex-smokers who had stopped for less than 3 months (OR 0.34, 95% CI 0.15-0.78) or at least 3 months (OR 0.24, 95% CI 0.09-0.67) than among continuing smokers. There was no change in anxiety measures in the general population or any increase in anxiety or depression symptoms in ex-smokers with a past history of these conditions.
CONCLUSIONS: Smoking cessation does not appear to be associated with an increase in anxiety or depression and may lead to a reduced incidence of depression.