Association between stress and breast cancer in women: a meta-analysis.

The objective of the current meta-analysis was to verify the association between stressful life events and primary breast cancer incidence in women. A total of 618 studies from 1982-2007 were found in the PubMed, LILACS, and Cochrane Library databases. Methodological quality was evaluated according to the Downs & Black criteria. Eight studies were selected (six case-controls and two cohorts). The studies were grouped in three analyses, two of which based on the categories widowhood and divorce and the other based on self-rated intensity and frequency of stressful events. Relative risks were: widowhood 1.04 (95%CI: 0.75-1.44; p = 0.800); divorce 1.03 (95%: 0.72-1.48; p = 0.850); and intensity/frequency of stress 1.73 (95%CI: 0.98-3.05; p = 0.059). We conclude that stressful life events as a whole are not associated with risk of breast cancer in women. However, it is not possible to rule out high-intensity stress as a risk factor for breast cancer.