Self-reported stress and risk of breast cancer

Many women attribute the development of their breast cancer to psychosocial factors such as stress and depression. Yet investigations of the relationship between breast cancer and stressful life events have had inconsistent outcomes, due in part to studies with small sample sizes and reliance on hospital-based populations.

As part of a population-based, case-control study of breast cancer etiology, we evaluated the association between stressful life events and the risk of breast cancer among 258 breast cancer patients and 614 randomly selected population-based controls. Information on 11 stressful life events was collected in telephone interviews with women aged 50-79 who were participating in the ongoing study.

Breast cancer patients and controls experienced the same number of stressful life events in the five years prior to diagnosis or an equivalent reference date (controls), averaging 2.4 and 2.6 events, respectively. After adjustment for known breast cancer risk factors, there was no association between weighted stressful life event scores and the risk of breast cancer (odds ratio [OR] = 0.90 per unit increase; 95% confidence interval [CI], 0.78-1.05). Only one life event, death of a close friend, was significantly more often reported by controls (OR = 0.72; 95% CI, 0.52-1.00). Other life events were inconsistently and nonsignificantly associated with breast cancer risk. CONCLUSIONS. The results of this retrospective study do not suggest any important associations between stressful life events and breast cancer risk.