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Understanding the impact of synthetic estrogens on mental health


Recent research has highlighted a potential link between synthetic estrogens used in birth control pills and increased anxiety behaviors in rats. This discovery raises questions about the long-term effects of these hormones on mental health.

The prevalence of combined hormonal contraceptive pills

The combined hormonal contraceptive pill, second only to condoms in popularity in the United States, has traditionally included the synthetic estrogen known as ethinyl estradiol. However, a shift towards more natural estrogen formulations is beginning to emerge.

Comparing synthetic and natural estrogens

Studies conducted on rats have shown that those administered synthetic estrogens exhibit more anxiety-related behaviors compared to those given a natural estrogen found in a newer contraceptive pill, Zoely. Zoely, which contains the natural estrogen NOMAC-E2, has been on the market since 2011 and is produced by Merck.

Abigail Hegwood, M.S., a Ph.D. candidate at Midwestern University, led the research, aiming to explore the differences between synthetic and natural estrogens in birth control pills and their potential side effects. The study’s findings were presented at ENDO 2024, the Endocrine Society’s annual meeting in Boston, MA.

Study findings and implications

The research involved three groups of female rats, each receiving different treatments over 28 days. The findings indicated that while spatial memory remained consistent across all groups, those treated with synthetic estrogen responded differently in maze tests, suggesting heightened anxiety levels.

Further analysis revealed that synthetic estrogens might affect the availability of steroid hormones in the body, which in turn could influence brain function and behavior. The study also observed that the natural estrogen produced in the ovaries was undetectable in over half of the rats given synthetic estrogen, pointing to a potential disruption in the body’s hormonal feedback loop.

Expert insights

Experts like Alesia Prakapenka, Ph.D., and Professor Jonathan Schaffir, MD, emphasize the importance of understanding the behavioral effects of hormonal contraception. While the impact on human behavior may be subtle, it’s crucial to continue research to develop contraceptives with fewer side effects and better physiological responses.

Future directions for birth control

The study underscores the need for tailored birth control options that consider individual responses and side effects. As research progresses, the goal is to provide women with informed choices about their contraceptive methods, aligning with their unique health profiles and life stages.

With ongoing development in hormonal treatments for menopause, similar strategies could be applied to contraceptives, offering a more personalized approach to women’s health.