Young girls who drink alcohol increase their risk of developing noncancerous breast disease, according to a joint study by Washington University School of Medicine and Harvard University. Benign breast disease is a risk factor for developing breast cancer.

Study participants diagnosed with benign breast disease reported an average daily alcohol consumption twice that of those who did not have benign breast disease. Those diagnosed also had more episodes of binge drinking.

"We know from many other studies of adult women that alcohol intake later in life increases breast cancer risk," said Dr. Graham Colditz with the Siteman Cancer Center at Washington University School of Medicine and Barnes-Jewish Hospital. "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."

Benign breast lesions can be a step in a pathway leading from normal breast tissue to invasive cancer, so the condition is an important marker of breast cancer risk, Colditz said.

The researchers studied nearly 7,000 girls ages 9 to 15 and followed them using health surveys from 1996 to 2007. The participants were part of Harvard University's Growing Up Today Study of girls from all 50 states. The study is unique, Colditz said, because it asked about alcohol intake while the participants were adolescents instead of asking them to recall many years later how often they drank.

Participants who drank six or seven days a week were 5.5 times more likely to have benign breast disease than those who didn't drink or who had less than one drink per week, the study showed. Participants who reported drinking three to five days per week had three times the risk.

The study, recently published in the journal Pediatrics, adds to evidence that steps can be taken to help prevent breast cancer.

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