Wearing a Bra in General…

There are few solid studies on bra wearing and breast cancer, but one of the most compelling was completed by medical anthropologists Sydney Singer and Soma Grismaijer -- authors of Dressed to Kill: The Link Between Breast Cancer and Bras. The study of over 4,000 women found that women who do not wear bras have a much lower risk of breast cancer:

Their findings included:

Women who wore their bras 24 hours per day had a 3 out of 4 chance of developing breast cancer
Women who wore bras more than 12 hour per day, but not to bed, had a 1 out of 7 risk
Women who wore their bras less than 12 hours per day had a 1 out of 52 risk
Women who wore bras rarely or never had a 1 out of 168 chance of getting breast cancer

When comparing women who wore their bras 24 hours a day with those who did not wear bras at all, there was a 125-fold difference in risk. Based on the results of this study, the link between bras and breast cancer is about three times greater than the link between cigarette smoking and cancer.

Although this study did not control for other risk factors, which could have skewed their results, other studies have found similar compelling links. For example, a group of Japanese researchers found that wearing a girdle or bra can lower your levels of melatonin by 60 percent. The hormone melatonin is intimately involved with the regulation of your sleep cycles, and numerous studies have shown that melatonin has anti-cancer activities.