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An Ode to Sex Hormones

Patricia C. Lopes
Oct 29, 2019 · 4 min read

What we do (and do not) know about being on the Pill

Photo by Ash Cork from Pexels

We are a long way from 1955, when the first large-scale oral birth control pill was tested on women in Puerto Rico. At that time, the medication’s potential side effects were unknown. “The pill” — a catchall term for oral hormonal contraceptives — now comes with a booklet containing an extensive list of possible side effects that go far beyond pregnancy prevention. These include an increased risk of deep vein thrombosis, myocardial infarction, hypertension, migraine, weight gain, and weight loss. Sarah Hill’s new book, This is Your Brain on Birth Control, synthesizes research on the unintended side effects of hormonal birth control with a goal of empowering women to make more informed decisions about what they are willing to tolerate in the name of reproductive control. The book fits superbly in a time when we are actively discussing reproductive rights in the United States.

Hill takes a bottom-up approach, starting with the physiological effects of hormonal birth control before proceeding to the psychological. From there, she expands on the pill’s implications at the network and demographic levels.

The book begins by introducing concepts from the field of animal behavior, such as sexual conflict, reproductive investment, and parent-offspring conflict before carefully describing the phases of the ovulatory cycle as well as how they impact female sexual behavior. Next, Hill delves into how the pill affects how women deal with stress, describes how women on the pill have a higher incidence of depression, and discusses the correlation between oral contraceptive use and an increased risk of suicide. The latter, we learn, is particularly pronounced in younger patients.

Heterosexual women who are not taking hormonal contraception tend to find traits like facial masculinity and low-pitched voices sexually attractive during the fertile (late follicular) phase of their cycles, while they tend to prefer more feminized versions of those traits during the luteal phase. By altering a woman’s hormonal profile, Hill argues, the birth control pill may therefore also alter her choice of mate. The research that supports parts of her thesis is still preliminary, but the idea is nonetheless compelling and worthy of further investigation.

“[U]ntil recently,” writes Hill, “women’s health has been all but completely ignored by science.”

She discusses the many underlying reasons for why research has traditionally been conducted on male subjects, including the fact that results tend to be more uniform when one sex is studied, and how the cyclical nature of female hormones can make studies more complex and potentially lengthier. The end result is that many health guidelines are based on data obtained from men and male animals; a tradition that has compromised our understanding of female physiology and, at times, jeopardized women’s health.

Ultimately, Hill’s main thesis is that if you change women’s hormones, you change women. This is a message ripe for misinterpretation. But as she writes,

“Anyone who tells you that biology is inconsistent with feminism doesn’t know what they’re talking about.”

Hormones affect everyone’s behaviors, she argues. Changes in testosterone, for example, have been associated with observing one’s favorite sports team win or lose, and interacting with guns, and it fluctuates in ways that are much less predictable than do those that govern the female menstrual cycle.

To that end, Hill does not advocate that women reject the pill out of hand.

“Granting women the ability to have sex without having to worry about rushing into marriage or parenthood… has been paramount in terms of allowing women the opportunity to achieve,” she acknowledges. “We probably owe countless specific achievements — technologies developed, cures discovered, people helped — to the birth control pill.”

Instead, she encourages all potential users to educate themselves about the medication’s potential effects, beyond pregnancy prevention, and to monitor their own experience closely. Each individual’s experience on the pill is unique and only the pill taker can assess whether and how strongly they experience documented side effects. (“[A]ll studies have [outliers]. It’s possible you might be one of them,” Hill notes.)

The book concludes with an outline for a conversation Hill hopes to have with her daughter one day about how to decide whether hormonal contraception is the right choice for her. “Although the science is still new and these conversations are just getting started,” she writes, “let today be the day that you begin one of your own.”

Virtually all prescription medication has risks associated with it and those risks must be balanced with the benefits. Having control over reproduction is an enormous benefit. My take-away from Hill’s book is that we perhaps know less than we should regarding certain risks associated with the pill. I therefore hope that this conversation will continue. It is not only our daughters who would benefit from evidence-based discussions about reproductive technology, but our neighbors, our doctors, and our political leaders as well.

Citation: Sara E. Hill. 2019. This Is Your Brain on Birth Control. The Surprising Science of Women, Hormones, and the Law of Unintended Consequences. Avery Publishing. ISBN 9780525536031

Patricia C. Lopes

Written by

Behavior, hormones, brains. Assistant Professor of Biology at Chapman University. Opinions are my own.

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