Is There Really a Connection Between Birth Control and Brain Cancer?

When it comes to oral contraceptives and cancer, the news is mostly reassuring. Taking the Pill offers solid protection against ovarian and uterine cancer. And though recent research suggests that the Pill can jack up your breast cancer risk, other research refutes this, according to Planned Parenthood.

But a new study linking birth control pills to brain cancer has left a lot of Pill takers panicking. The study, from the British Journal of Clinical Pharmacology, looked at the incidence of a brain cancer called glioma among younger women in Denmark. Curious about whether the hormones in the pill had an affect on glioma, the research team poured through health registries, IDing all the Danish women between ages 15 and 49 who were diagnosed with glioma between 2000 and 2009. They then looked into how many of these women had an Rx for birth control pills, recording the type they took (either the estrogen-progestin “combo pill” or the progestin-only “minipill”) and for how long. Finally, they compared them to a control group of glioma-free women in the same age range.

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The results showed a 50 percent higher risk of glioma in women who took any pill type for any length of time. Scarily, the risk doubled among women who took progestin-only pills for at least five years. “Long-term hormonal contraceptive use may increase the risk of glioma,” concluded the study authors.

So does this mean birth control pills, especially the progestin-only kind, caused the boost in risk? Not at all.

“This study shows correlation but not causation, and we can’t be sure that another factor wasn’t responsible for the link,” says Alyssa Dweck, M.D., ob-gyn in Westchester, New York, and coauthor of V Is for Vagina (Dweck was not involved in the study). The research team wrote this in the study, suggesting that the rates may have been higher in Pill takers because women on oral contraceptives might be more likely to visit their doctor. The researchers also raised the possibility that BMI played a role, as overweight women are more likely to be prescribed progestin-only pills because these have fewer side effects, such as blood clots. But the researchers were not able to control for BMI, so they just don’t know.

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It’s also important to remember that glioma is super rare, with about five in 100,000 women developing it. “Doubling the risk still means only 10 women out of 100,000 will have it, which is not a lot,” says Dweck.

Bottom line: Don’t toss your Pill pack because of one alarming study; there’s no evidence that the Pill’s hormones have any effect on your glioma risk. “When put in context, the benefits of hormonal contraception clearly outweigh risk,” says Dweck. “Even the researchers say that the study should not be taken as a reason to stop using birth control pills.”

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