A prospective study of life satisfaction, neuroticism and breast cancer risk (Finland)

Objective: To prospectively investigate whether life satisfaction and neuroticism, two measures reflecting aspects of anxiety/depression, are related to risk of breast cancer. Methods: The study population comprised 12,032 women from the population-based Finnish Twin Cohort. Life satisfaction and neuroticism were assessed in health questionnaires in 1975 and 1981. During 21 years of follow-up, 238 cases of breast cancer were documented in the study cohort through record linkage to the Finnish Cancer Registry. Results: After adjustment for age and other important covariates, the hazard ratios were 1.0 (reference), 0.9 (95% confidence interval 0.6-1.3) and 1.0 (0.7-1.6) by decreasing level of life satisfaction (satisfied, intermediate, dissatisfied), and 1.0 (reference), 1.0 (0.7-1.4) and 0.8 (0.6-1.2) by increasing level of neuroticism (low, intermediate, high). These results did not change after accounting for possible changes in the levels of life satisfaction and neuroticism between 1975 and 1981. The null results were also confirmed with the use of a nested case-control study within twin pairs that became discordant for breast cancer during the follow-up. Conclusions: Our data indicate that life satisfaction and neuroticism are not substantially associated with breast cancer risk. These findings provide epidemiological evidence against the doubts that breast cancer would be more likely to occur in unhappy, dissatisfied, and worrying women.