Is it true that the pill causes brain tumours?
(Link): Is it true that the pill causes brain tumours? by S. Gage
- Headlines today are pretty scary for the estimated one third of 16-49 year old women in the UK who use hormonal contraception, warning that doing so could ‘double the risk of brain tumour’. But these tumours are so rare that a doubling in risk actually only equates to one extra case per 50,000 women taking the contraception per year.
- Hormonal contraceptives are very widely used in the UK, and provide a near-perfect method of birth control. A story that suggests they are harmful could lead women away from using them, potentially stopping any form of birth control at all, and increasing their risk of unwanted pregnancies and the health risks that can go along with that.
- …. Using these data, the authors of the study found that women who developed gliomas were more likely to have used hormonal contraception than those who did not, after taking in to account years of schooling, and history of allergy or asthma.
- Does this mean hormonal contraception caused the increased risk? It’s not possible to tell from these findings, as the authors of the study make plain in their paper.
- Whenever you observe groups of people, rather than randomly split them to either receive the intervention or not, you can never be completely sure that there aren’t other differences between the groups that could be causing the association seen. For example, obesity is thought to impact on glioma rates, but data on this was not available for the women included in this study.
- Aside from the findings in this paper, there is also some evidence that hormonal contraception could be protective against ovarian cancer, cancer of the womb, and bowel cancer, all of which are more common than these brain tumours.