London, July 15 (IANS): Women with low levels of an anti-stress hormone have an increased risk of getting breast cancer, says a new study.

The study focused on a hormone which circulates freely in the blood, enkephalin, with pain- and anxiety-reducing properties. Enkephalin also reinforces the immune system by directly affecting immune cells.

"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, professor at Lund University, Sweden.

The study that appeared in the Journal of Clinical Oncology, was based on blood samples taken from over 1,900 women. The average age of the women studied was 57. The women were followed up with regard to breast cancer for an average period of 15 years.

The researchers said geographical location and age, in spite of the adjustments in the study, may be significant. After further studies, the results will facilitate prevention and early detection of breast cancer.

For those with an increased risk of breast cancer, potential preventive treatments could take the form of lifestyle interventions to reduce stress and new drugs.

"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 co-author Mattias Belting and professor at Lund University, Sweden.