Does smoking cessation improve mental health?

There is a possibility that cessation of smoking improves mental health, bu t there are no studies that have demonstrated this. A cohort study was perf ormed for 1 year in 18 males who spontaneously stopped smoking (cessation g roup) and 173 who continued to smoke (smoking group). The mental health sta te was evaluated using the Japanese version of the 30-item General Health Q uestionnaire (GHQ-30) before the cessation of smoking and 6 months and 1 ye ar after smoking cessation. Changes in the GHQ score were compared between the cessation and smoking groups. In order to control the effects of confou nding factors, multiple regression analyses were performed using the GHQ sc ore 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 c essation (P < 0.04 and 0.01, respectively, by paired t-test). In the smokin g group, the GHQ score slightly decreased. Repeated measure analysis of var iance revealed that the decrease in the GHQ score in the cessation group wa s significantly larger than in the smoking group. Multiple regression analy sis revealed significant effects of smoking cessation on mental health afte r controlling for other confounding factors. It can be concluded that smoki ng cessation may improve mental health.