The association between smoking, smoking cessation and mental health

Introduction: Smoking is a major risk factor for development of serious disease and smoking cessation greatly reduces this risk. The association between smoking, smoking cessation and mental health however, is less clear-cut, therefore this thesis aimed to further investigate this association. Methods: The first part of the thesis reports a systematic review and meta-analysis of longitudinal studies to determine the difference in change in mental health between quitters and continuing smokers. The second part of the thesis reports three prospective analyses of individual level-patient data from five trials for smoking reduction treatment. The first analysis examined the association between cessation and change in mental health using propensity score matching (PSM). The second analysis examined the association between cessation and risk of psychiatric disorder using PSM. The final analysis examined the association between change in mental health after quitting and odds of relapse. Results and interpretations: Cessation was associated with improvements in mental health compared with continuing smoking; there was no association between cessation and risk of psychiatric disorder, and no association between change in mental health after cessation and future relapse. Results support the misattribution hypothesis, and have implications for future research, smoking cessation treatment and public health policy