“Wearing a bra causes breast cancer.”

The widespread belief that wearing a bra, particularly an underwire bra, can lead to breast cancer often traces back to a 1995 book titled "Dressed to Kill: The Link Between Breast Cancer and Bras." The authors proposed that bras restrict the lymphatic system, thereby preventing the body from expelling toxins and trapping them in the breasts, ultimately causing cancer. This theory gained traction and was widely circulated, especially online, despite lacking scientific support.

However, numerous scientific studies have thoroughly investigated this claim and found no evidence to support it. A significant population-based case-control study conducted in 2014, for instance, examined over 1,500 postmenopausal women and concluded that no aspect of bra-wearing, including cup size, the presence of an underwire, the number of hours worn daily, or the age at which bra use began, was linked to an increased risk of breast cancer. Leading health organizations like the American Cancer Society, National Cancer Institute, and Susan G. Komen Foundation (Review) also confirm that there is no scientific basis for this myth. Experts consistently point out that the biological plausibility of bras impeding the lymphatic system in a way that causes cancer is extremely weak.

The myth persists for several reasons. The idea that compression can block the lymphatic system sounds plausible to many, even though experts state the lymphatic system is not easily restricted by clothing. Additionally, some observational data from earlier studies, like a 1991 study, showed a correlation where premenopausal women who didn't wear bras had a lower risk of breast cancer. However, this finding was not statistically strong and could be explained by other factors, such as body weight and breast size, which are actual risk factors for breast cancer. Women with larger breasts are more likely to wear bras for support and also tend to have a higher body weight, which is a known risk factor for breast cancer, thus creating a misleading association. People also often seek simple, controllable explanations for complex diseases like cancer, making such myths emotionally appealing, even if untrue.