Do Birth Control Pills cause Brain Tumors?

A recent press release suggested that exposure to hormonal contraceptives (birth control pills or BCP) was associated with an increase in brain tumors.

In the actual study, in Denmark, researchers looked at 300 women with gliomas, a kind of brain tumor, and matched them with 2000 similar women without the tumor. They found that 59% of women with tumors had used BCP, while only 50% of controls had.

While this is suggestive of a cause and effect, the risk was so low it is not cause for major alarm. As well, use of BCP is associated with lower risk for certain other tumors so the overall risk is probably insignificant.

However, they did discover that progesterone only BCPs had a much higher association. Curiously, it is also the progesterone in post-menopausal hormone treatment that seems associated with breast cancer.

It would be appropriate not to use progesterone only BCPs as a result of this study.