The relation between stressful life events and breast cancer: a systematic review and meta-analysis of cohort studies.

PURPOSE: Breast cancer is the most common cancer among women with high rate of mortality. This systematic review and meta-analysis was conducted to investigate the relation between stressful life events and breast cancer.

METHODS: We searched PubMed, Scopus, ScienceDirect, and Google scholar databases from their inception until June 2018. The keywords and phrases we used in the search were (life events AND stress AND breast cancer OR neoplasm) to identify potentially relevant cohort studies that reported relative risk estimates and confidence intervals of this association. Pooled Risk ratio and 95% confidence intervals (CIs) were calculated using random effects model.

RESULTS: Out of 168 potentially relevant publications, 11 documents met the inclusion criteria. The results showed that history of stressful life events slightly increases the risk of breast cancer [pooled Risk Ratio: 1.11 (95% CI 1.03 to 1.19)].

CONCLUSIONS: History of stressful life events could be associated with a moderate increase in the risk of breast cancer. We advise that receiving psychological and counseling services after occurrence of stressful life events of women should be taken seriously.