Personality traits, health behavior, and risk for cancer - A prospective study of a Swedish twin cohort

BACKGROUND. The authors conducted a prospective investigation into the relation between personality traits and the risk for cancer. METHODS. The Study cohort consisted of 29,595 Swedish twins from the national Swedish Twin Registry who were ages 15-48 years at time of entry. In 1973, the twins completed a questionnaire eliciting information on personality traits and health behavior. The Eysenck Personality Inventory was used to measure neuroticism and extroversion as two personality dimensions. A Cox proportional hazards model was used to estimate hazard ratios and 95% confidence intervals for extroversion and neuroticism separately as well as for their joint effect, and conditional logistic regression analyses were conducted to estimate the relation between personality traits and risks for cancer in twin pairs who were discordant for cancer. All analyses were conducted for six etiologicallv different groups of cancers: hormone-related organ cancers, virus-related and immune-related cancers, digestive organ cancers (excluding liver), respiratory organ cancers, cancers in other sites, and all cancer sites. RESULTS. Follow-tip in the Swedish Cancer Registry for 1974-1999 revealed 1898 incidents of primary cancer. The authors found no significant association between neuroticism, extroversion, their joint effects and the risk for any cancer group. CONCLUSIONS. The current results did not Support the hypothesis that certain personality traits are associated with cancer risk. (C) 2005 American Cancer Society.