Personality risk factors of occurrence of female breast cancer: a case-control study in China.

To investigate the association of personality traits with breast cancer risk, a case-control study was conducted from May 2014 to February 2017, in which the case group consisted of 262 women with breast cancer and 262 without (control group). The Eysenck Personality Questionnaire (EPQ) (88-question Adult Edition) and another self-assessment questionnaire that contained open questions to obtain more specific character traits were used to complete this survey. The results of the E scale showed that 121 women (46.18%) in the case group and 94 women (35.88%) in the control group were extroverted. The results of the N scale showed that 150 women (57.25%) in the case group and 86 women (32.82%) in the control group had unstable personality. Adjusting for other confounding factors, extroversion and unstable personality were risk factors for breast cancer (E scale: OR = 1.70, 95% CI = 1.28-2.15; N scale: OR = 3.18, 95% CI = 1.77-4.91). Personality instability was a higher risk factor than extroversion was. People with unstable personalities were 3.18 times more likely to have breast cancer than were those who had stable personalities. The results of the self-assessment questionnaire suggested that the more frequent character traits mentioned were being concerned over everything, irritable, and perfectionistic, seeking to prevail over others, and being manipulative and oversensitive.