One of the first things a person does when diagnosed with breast cancer is to wonder what caused it.  Women start thinking about everything that might have affected their breasts.  Could it have been that tight bra?  Could that letter circulating on the internet about antiperspirants causing breast cancer be right?  Did that recent divorce or death in the family cause their breast cancer?

Many researchers are wondering what causes breast cancer too, and so far no one knows for sure.  We do know some risk factors for breast cancer, but risk factors and causes are different.   A risk factor is a condition that is more common in people with the disease.  One risk factor for breast cancer, for example, is age.  We know that older women are much more likely than younger women to get breast cancer and that the majority of breast cancer patients are over sixty.  Does age cause breast cancer?  Of course not.  The majority of elderly women do not get breast cancer.

When scientists are researching the cause of a disease, they start looking for correlations among the people who have that disease.  A well-known example is tobacco smoking and lung cancer.  Scientists started noticing that lung cancer rates had risen as the number of people smoking had risen and that most people with lung cancer were smokers.  This high correlation between tobacco use and lung cancer led scientists to hypothesize that smoking might be one cause of lung cancer.

The tobacco industry fought back saying this conclusion was shoddy science.  Maybe some third factor was causing the rise in lung cancer, not smoking.  Correlation and causation are not the same.  But the scientists tested out their hypothesis and were able to show that tobacco is in fact a carcinogen.

In this article, I'll look at three factors that have a high correlation with breast cancer but which do not cause it:  bras, antiperspirants, and stress.  In later articles, I'll discuss some risk factors that may give clues to the causes of breast cancer.

Bras.  One theory is that bras cause breast cancer, especially tight bras or underwire bras.  Almost every women in the United States who gets breast cancer wears a bra.  There is an extremely high correlation between bra wearing and breast cancer.  Unfortunately this theory ignores the fact that almost every woman in the United States who does not get breast cancer also wears a bra.

Breast cancer happened to women well before the invention of the bra in the 1920's.  It happens to women in cultures where bras are not worn.  Dr. Susan Love, breast cancer expert, says, "Wearing a bra is neither physically harmful nor medically necessary."  She dismisses the theory that wearing an underwire bra could cause cancer as "total nonsense."

Antiperspirants and deodorants.  Another habit with a high correlation to breast cancer is using antiperspirants or deodorants.  Again in the United States, most women use these products, so it is not surprising that most women who get breast cancer have used them.  The theory goes that antiperspirants block the elimination of sweat and somehow cause toxins to build up that cause cancer.