Women who used increased amounts of antibiotics appear to have a greater risk of breast cancer, according to a new study published in The Journal of the American Medical Association (JAMA). However, the researchers point out that more studies are needed to determine if the association between breast cancer and antibiotics is causal or if there are other underlying factors to be considered.

"Breast cancer is the most frequently diagnosed nonskin malignancy and the second leading cause of cancer mortality in U.S. women," according to background information from the authors. "It is also the most common cancer in women worldwide, with more than 1 million cases diagnosed each year. Antibiotics are used extensively and overused in many countries, though efforts are underway to curb overuse."