Does smoking cessation improve mental health?

There is a possibility that cessation of smoking improves mental health, but there are no studies that have demonstrated this. A cohort study was performed for 1 year in 18 males who spontaneously stopped smoking (cessation group) and 173 who continued to smoke (smoking group). The mental health state was evaluated using the Japanese version of the 30-item General Health Questionnaire (GHQ-30) before the cessation of smoking and 6 months and 1 year after smoking cessation. Changes in the GHQ score were compared between the cessation and smoking groups. In order to control the effects of confounding factors, multiple regression analyses were performed using the GHQ score after 6 months and 1 year as dependent variables. The GHQ score in the cessation group significantly decreased 6 months and 1 year after smoking cessation (P < 0.04 and 0.01, respectively, by paired t-test). In the smoking group, the GHQ score slightly decreased. Repeated measure analysis of variance revealed that the decrease in the GHQ score in the cessation group was significantly larger than in the smoking group. Multiple regression analysis revealed significant effects of smoking cessation on mental health after controlling for other confounding factors. It can be concluded that smoking cessation may improve mental health.