Systematic computerized searching of the PubMed, ScienceDirect, Embase, and BMJ databases with the combinations of controlled descriptors from Mesh, including breast cancer, breast tumor, cancer of breast, mammary carcinoma, life events, life change events, case--control studies, case-base studies, cohort study, and cohort analysis and identified a total of 307 papers published from January 1995 to April 2012. Following evaluation of methodological quality with the Downs & Black criteria, seven case--control or cohort studies were selected and the association between striking life events and primary breast cancer incidence in women was measured using random effect or fixed-effect odds ratios combined with 95% confidence interval.

The seven studies included in the final meta-analysis included 99,807 women. A meta-analysis showed that the pooled OR for striking life events and breast cancer was 1.51 (95% CI 1.15 - 1.97, P = 0.003), indicating that women with striking life events were at 1.5-fold greater risk of developing breast cancer. The pooled OR for severe striking life events and breast cancer was 2.07 (95% CI 1.06 - 4.03), indicating that women with severe striking life events were at 2-fold greater risk of developing breast cancer.

The current meta-analysis showed significant evidence for a positive association between striking life events and primary breast cancer incidence in women.