For decades, researchers attempted to determine whether stress might increase breast cancer risk, with some studies reporting an increase after adverse life events.
Results of a prospective study consisting of more than 105,000 women have shown, however, that “it is unlikely that stress is implicated in causation of breast cancer,” Minouk Schoemaker, PhD, of the division of genetics and epidemiology at The Institute of Cancer Research in London, United Kingdom, told Cancer Therapy Advisor.1
“From surveys, it is known that when women with breast cancer are asked why they think they have developed the disease, stress is among the most commonly cited reasons,” she added. “They are less likely to cite established causes, and I think it is unlikely this perception could radically change in the short-term.”
To determine whether frequency of stress and adverse life events affect breast cancer risk, the investigators examined data from the Breakthrough Generations Study, which focuses on breast cancer etiology. More than 113,000 women ages 16 and older completed a postal questionnaire that asked whether “they had been experiencing stress over the last 5 years,” and provided blood samples.
Also asked was whether “they had experienced: death of a husband or long-term partner; death of a child, parent or other close relative; death of a close friend; divorce or separation; serious personal illness or injury; loss of a job; or another life event that they found very stressful,” the authors wrote in Breast Cancer Research.
The analysis was based on 106,612 women without a history of breast cancer who were enrolled from 2003-2012. Follow-up questionnaires were available for 94.6%; 1.7% had developed breast cancer; 0.7% had died, 2.6% were alive and had not completed the questionnaire, but data were available from the National Health Service Central Registers, and 0.4% were lost to follow-up.
Among the 1783 women who developed breast cancer, 1510 had first invasive and 273 had in situ disease; estrogen-receptor status was known for 99.3% and 57.5%, respectively.
Breast cancer risk was reduced among women who had a close relative die within 5 years of study entry; relative risk (RR) was 0.87 (95% CI, 0.78-0.97). An increased association was observed in those younger than 20 years when their mothers died (RR 1.31; 95% CI, 1.02-1.67), though this risk was attenuated after mothers with breast or ovarian cancer were excluded (RR 1.17; 95% CI, 0.85-1.61).
Losing one’s parents during childhood and adolescence, death of a spouse or partner or close friend, personal illness or injury, or divorce or separation did not increase breast cancer risk.
A positive association was found between divorce and estrogen-receptor (ER)–negative breast cancer (RR 1.54; 95% CI, 1.01-2.34), “probably due to chance,” she said.
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“Psychological stress is unlikely to increase breast cancer risk, but long-term stress should be avoided because it might have other health effects and, additionally, people under stress may develop certain behaviors such as smoking, overeating, or drinking alcohol, which increase people’s risk of cancer,” Dr Schoemaker said.
The investigators hope to repeat this analysis in 5 years, with larger numbers of women with ER-negative breast cancer. “We will also be able to explore the role of age at diagnosis in more detail than currently possible,” she said.
- Schoemaker MJ, Jones ME, Wright LB, et al. Psychological stress, adverse life events, and breast cancer incidence: a cohort, investigation in 106,000 women in the United Kingdom. Breast Cancer Res. 2016;18(1):72. doi: 10.1186/s13058-016-0733-1