New research suggests that an anti-stress hormone could help predict a woman's risk of developing breast cancer.

Researchers at Lund University found that women with low levels of the hormone enkephalin have an increased risk of getting breast cancer. The hormone is comprised of pain- and anxiety-reducing properties, and also reinforces the immune system by directly affecting immune cells.

"This is the first time the role of enkephalin in breast cancer has been studied in humans, and the results were surprisingly clear. Among women with the lowest levels of the hormone, the risk of breast cancer was more than three times that of the women with the highest levels of the hormone. This is one of the strongest correlations between cancer risk and a freely circulating biomarker ever described," said Olle Melander and Mattias Belting, both professors at Lund University and consultant physicians at Skåne University Hospital.

For the study, researchers collected and analyzed data from more than 1,900 women. The women were followed up with regard to breast cancer for an average period of 15 years.

They found a correlation between low encephalin concentration in the blood and increased risk of breast cancer. However, it is still unclear whether there is a causal relationship between the two.

Researchers hope that after further studies, the results will facilitate prevention and early detection of breast cancer.

"Our immediate plan is to investigate how to affect the level of enkephalin in healthy individuals. We will do this primarily in a study with a smaller number of women. We are also interested in the hormone's role in other cancers," said the researchers.

The findings are detailed in the Journal of Clinical Oncology.