The participants who were diagnosed with benign breast disease on average drank more often, drank more on each occasion and had an average daily consumption that was two times that of those who did not have benign breast disease. They also had more episodes of binge drinking.

The study is unique because it asked about alcohol intake while participants were adolescents instead of asking them to recall many years later how often they drank.

"We know from many other studies of adult women that alcohol intake later in life increases breast cancer risk," Colditz says. "But many women begin drinking alcohol as adolescents right at the time in which breast tissue is going through stages of rapid proliferation. So we wanted to see if the effect of alcohol on breast cancer risk was operative in this younger group."

The results of this study provide more evidence that steps can be taken to prevent breast cancer.

"There's growing evidence that physical activity can lower breast cancer risk," Colditz says. "We also know that diet and weight are important factors. Now it is clear that drinking habits throughout life affect breast cancer risk, as well."

SOURCE Washington University School of Medicine, St. Louis and Harvard University