Personality and smoking: individual-participant meta-analysis of nine cohort studies.

AIMS To investigate cross-sectional and longitudinal associations between personality and smoking, and test whether socio-demographic factors modify these associations. DESIGN Cross-sectional and longitudinal individual-participant meta-analysis. SETTING Nine cohort studies from Australia, Germany, the United Kingdom and the United States. PARTICIPANTS A total of 79 757 men and women (mean age = 50.8 years). MEASUREMENTS Personality traits of the five-factor model (extraversion, neuroticism, agreeableness, conscientiousness and openness to experience) were used as exposures. Outcomes were current smoking status (current smoker, ex-smoker and never smoker), smoking initiation, smoking relapse and smoking cessation. Associations between personality and smoking were modelled using logistic and multinomial logistic regression, and study-specific findings were combined using random-effect meta-analysis. FINDINGS Current smoking was associated with higher extraversion [odds ratio per 1 standard deviation increase in the score: 1.16; 95% confidence interval (CI) = 1.08-1.24], higher neuroticism (1.19; 95% CI = 1.13-1.26) and lower conscientiousness (95% CI = 0.88; 0.83-0.94). Among non-smokers, smoking initiation during the follow-up period was predicted prospectively by higher extraversion (1.22; 95% CI = 1.04-1.43) and lower conscientiousness (0.80; 95% CI = 0.68-0.93), whereas higher neuroticism (1.16; 95% CI = 1.04-1.30) predicted smoking relapse among ex-smokers. Among smokers, smoking cessation was negatively associated with neuroticism (0.91; 95% CI = 0.87-0.96). Socio-demographic variables did not appear to modify the associations between personality and smoking. CONCLUSIONS Adult smokers have higher extraversion, higher neuroticism and lower conscientiousness personality scores than non-smokers. Initiation into smoking is associated positively with higher extraversion and lower conscientiousness, while relapse to smoking among ex-smokers is associated with higher neuroticism.