High levels of daily stress appear to result in a lower risk ofdeveloping breast cancer for the first time, says a study in thisweek's British Medical Journal.
But high stress may put women at risk of other serious illnesses warn the researchers, a team from Denmark.
The findings follow an eighteen year study of over 6,500 womenin Copenhagen. At the start of the study researchers asked the womenwhat levels of stress they experienced routinely in their lives, andclassified the results into low, medium and high levels. Stress wasdefined as tension, nervousness, impatience, anxiety, or sleeplessness.(Stress levels were not measured throughout the study.) In calculatingthe effects of stress, researchers also adjusted the results for otherfactors, such as whether they had children or whether they weremenopausal, which would have an influence on developing breast cancer.They did not account for risk factors such as family history of thedisease however.
Of the 251 women diagnosed with first-time breast cancer overthe study period, researchers found that women reporting high levels ofstress were 40% less likely to develop breast cancer than womenreporting low levels of stress.
The study further found that, for every increased level ofstress on a six-level scale, women were 8% less likely to developbreast cancer.
One explanation for the findings may be that sustained levelsof high stress may affect oestrogen levels - which, over time, may havean influence on developing breast cancer. But this theory has not beentested, and research in this area so far has mainly been restricted toanimals, caution the authors.
Despite the findings, the authors warn that stress-inducedchanges in hormonal balances are not a healthy response, and continuedstress may play a damaging part in other illnesses - particularly heartdisease.
Self reported stress and risk of breast cancer: prospective cohort study BMJ Volume 331, pp548-50
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