We've seen convoluted research linking birth control to a variety of cancers before. But, a new study is now making the rounds — it suggests that hormonal birth control may increase the risk for developing brain cancer in particular.
The study, published recently in the British Journal of Clinical Pharmacology, looked at data for 317 women with brain cancer (glioma) and 2,126 without collected from Danish health and administrative registries. The women were between 15-49 years old and had a similar number of years of education. The researchers looked at the women's prescription data and categorized them based on how long they had been using hormonal birth control (less than a year, 1-5 years, or over five years) and the type of birth control they were using (progestogen-only or progestogen and estrogen).
The study authors reported that women who had ever used the pill had a "moderately increased risk" for developing brain tumors than those who had never used it, and the risk increased the longer women were on that form of birth control. The risk also went up if the birth control was progestogen-only. The research also showed a heightened risk in those using hormonal intrauterine devices (IUDs), but the risk was lower than for those on the pill.
More than anything else, though, the connection is complicated. Other research linking brain cancer to hormone exposure has turned up weak or contradictory results. But, many of those studies relied on self-reported retrospective data and focused on women over the age of 50. This new study included more young women, and the data was collected through more reliable sources. Still, the study doesn't necessarily suggest a causal link and may be overlooking other potential factors, such as obesity. Previous studies have also linked use of the pill to both increased and decreased risks for developing cancers, including breast, ovarian, and endometrial cancers.
Correction: An earlier version of this article incorrectly stated that women who had ever used the pill had a 40% higher risk for developing brain cancer.