Career women with rough lifestyles may be protected against breast cancer, researchers have discovered.
High levels of daily stress reduce the chances of developing the disease by 40 per cent, they report in the British Medical Journal.
The finding runs counter to previous research which has suggested an increased risk of breast cancer in those under stress. Stress may also raise the risk of other diseases.
But the researchers from Denmark who conducted the latest study say sustained high levels of stress may reduce levels of estrogen - the female hormone - which is known to affect the development of breast cancer, reports Independent.
According to Reuters, scientists from Denmark drew their conclusions after studying 6,689 women over a period of 18 years, and speculated that it may be because daily stress suppressed production of estrogen, which is a risk factor in breast cancer.
"Prolonged-low key stress of everyday life results in a persistent activation of stress hormones which may impair estrogen synthesis and may therefore be related to lower risk of breast cancer," they wrote.
However, they pointed out that this theory was untested and deserved greater investigation.
Not only did the researchers from the National Institute of Public Health in Copenhagen find a lower incidence of primary breast cancer among stressed women, they found that the higher the day-to-day stress levels the lower the risk.
However, they warned that stress was not a health cure, given that high levels had also been associated with increased risk of potential killers like heart disease.