Most women will use some form of birth control for the majority of their adult lives. However, the side effects are not always clearly communicated and there are few effective alternatives to estrogen based contraceptives. Much has been done to study the relationship between oral contraceptives and breast cancer as the rate of breast cancer increases.
The meta-analysis by Kahlenborn, Modugno, Potter, & Severs (2006) looked at 34 studies conducted before 1980 involving oral contraceptive use and breast cancer detected before menopause. Across all of the studies there was a strong correlation between contraceptive use and breast cancer. They found that there is no effect on length of time taken for risk of development for women who do not have children. However, risk decreased among women who gave birth if they waited until after their first child to take oral contraceptives. There are known problems with using meta-analysis for confirmation, studies may be picked in a way that introduces bias and there is publication bias. Also, the doses of hormone in birth control has varied significantly when the women studied would have been taking it. This study demonstrated that there is a consistent relationship. The women involved in these studies ranged across SES, race and many other factors.
A Swedish case-control study by Jernström et. al (2005) was conducted using questionnaires and chart readings. They focused on women who had started birth control before age 20. They found that for every year before 20 that women had taken birth control, their was a significant increase in cancer risk. They acknowledged the possibility of recall bias but they confirmed their findings with the available medical history. This study demonstrated temporal causality.
This does not mean this hypothesis is universally accepted. The study by Westhoff (1999) accepted the opposite of the hypothesis in the other articles even though they had almost the same results. She associates the increased incidence of breast cancer with population growth instead of the popularity of birth control. Although increased risk of breast cancer is gone after 10 years of being off oral contraceptive, it does not diminish the effect that it could possibly have during those years. Also some women take contraceptive for reasons other than contraception even after menopause. When women develop breast cancer who are still using oral contraceptives, they have less serious diagnoses. This could be a surveillance effect since they have more routine checkups in order to obtain the contraceptives.
None of the studies I reviewed touched on specific types of contraceptives used and dosage levels. Further evidence in this area would support or could disprove the hypothesis if it indicates a plausible or coherent argument.
References
Friis, R. H. (2012). Essentials of environmental health. Sudbury, MA: Jones and Bartlett.
Jernström, H., Loman, N., Johannsson, O. T., Borg, Å, & Olsson, H. (2005). Impact of teenage oral contraceptive use in a population-based series of early-onset breast cancer cases who have undergone BRCA mutation testing. European Journal of Cancer, 41(15), 2312-2320. doi: 10.1016/j.ejca.2005.03.035
Kahlenborn, C., Modugno, F., Potter, D. M., & Severs, W. B. (2006). Oral contraceptive use as a risk factor for premenopausal breast cancer: A meta-analysis. Mayo Clinic Proceedings, 81(10), 1290-1302. doi: 10.4065/81.10.1290
Westhoff, C. (1999). Breast cancer risk: Perception versus reality. Contraception, 59(1), 25S-28S. doi: 10.1016/S0010-7824(98)00134-6
