Abstract
Consistent scientific evidence on the possible relationship between psychologic variables and breast cancer development is lacking. In 1996, our group first reported on the present prospective, longitudinal study. We found a weak association between a high score on the antiemotionality scale (indicating an absence of emotional behavior or a lack of trust in one's own feelings) and the development of breast cancer. No associations were found between any of the other 10 studied personality traits and breast cancer development. However, the study had a relatively short follow-up and did not investigate interaction effects between various personality traits. Therefore, the current follow-up study was conducted with the same cohort, which included the 9705 women who attended a biennial population surveillance program for breast cancer and completed a self-report personality questionnaire between January 1, 1989, and December 31, 1990. Women who developed breast cancer during the period from May 17, 1995, through January 1, 2003, formed the case group (n = 217) and were compared with age-matched women without breast cancer who formed the control group (n = 868) with regard to personality traits and medical risk factors for breast cancer. None of the personality factors were statistically significantly associated with an increased risk of breast cancer, with or without adjusting for the medical risk factors. Also, the occurrence of a combination of various personality traits (eg, a so-called cancer-prone personality) was not related to breast cancer development.