ANAt a time when women's reproductive freedoms are under attack, any suggestion that the birth control pill may be problematic seems explosive. Sarah E Hill, professor of social psychology at Texas Christian University in Fort Worth, Texas, argues that we need to talk about how oral contraceptives are affecting women's thinking, emotions, and behavior. How the Pill Changes Everything: Your Brain in Birth Control It's your new book on the science behind a sensitive subject.
Some US states have recently made abortion more difficult and the Trump government is doing its best to chisel away at access to birth control. Is your book trying to dissuade women from using the pill?
My institution was founded as a Christian school, but it has no specific religious bent now. My goal with this book is not to take the pill or alarm women. It is to give them information they did not have so far so they can make informed decisions. The pill, along with safe and legal abortions, are the two biggest keys to women's rights. But we also have a blind spot in thinking about how altering women's sex hormones – which is what the pill does – influences their brains. For a long time, women experience "psychological" side effects on the pill, but no one has told them why.
The reaction we are seeing against the pill, especially with millennial women drifting away, I think is because women didn't feel good about it and got tired of doctors patting their heads and saying they were wrong. The more information women have, the more it will bring them back to the pill.
How exactly does the pill affect women's brains?
The pill works primarily by mimicking the second half of a woman's monthly ovulatory cycle, in which progesterone hormone is dominant. Its main ingredient is artificial progesterone – called progestin – which turns off the brain signal that stimulates egg development. But it also means that the ovaries are not producing estrogen, the hormone that dominates the first half of a woman's natural cycle. And estrogen does some of our favorite things in our brains and bodies, making us feel sexier and more energetic. While most pills include some synthetic estrogen – mostly to compensate for the unpleasant side effects of progestin – women may miss it.
A less well understood mechanism is that progestins, which are usually created by altering the molecular structure of testosterone, are not an exact match for our progesterone receptors. This means that they can potentially stimulate other receptors, including testosterone receptors, leading to masculinizing effects, and cortisol, which over time can deregulate the stress response. Research suggests that the stress hormone profile in women taking pills is similar to people who have experienced chronic stress. Other research has found effects on the immune system, learning and memory.
We know a lot about the small but serious health risks associated with the pill – things like stroke and blood clots. Why were we kept in the dark about brain effects?
Until very recently, there was little research. And the research that is out there, doctors are often unaware because it is not being published in the medical journals they examine, but in the journals of psychology and neuroscience. So society has taboos about talking about it. The best defense against the sexist notion that women's hormones make them less rational than men seemed to deny hormonal involvement in the brain. And the pill is so useful that no one is motivated to examine it very critically. But our hormones, especially our sex hormones, are an essential part of what creates the experience of feeling like ourselves. And talking critically about the pill does not mean that the benefits do not outweigh the cost. It is not unethical for women to talk about these things.
How does the pill potentially affect women's choice of partner?
Estrogen is known to stimulate women's preferences when it comes to their romantic partners for qualities associated with masculinity and higher testosterone: square-cut jaws, broad shoulders, and forehead furrows, for example. But research suggests that women taking pills – in their state of artificial progesterone dominance and without a cyclic desire for estrogen – seem to prefer the faces of less masculine men. The implication is that if a woman chooses her partner when taking the pill and taking it, it can lead to relationship dissatisfaction because she is no longer attracted to the person. It's a possibility that women have at least in mind.
What about the mood swings women report about the pill?
Taking the pill is associated with an increased risk of being diagnosed with anxiety and depression, although some women report that the pill stabilizes their mood. The association was particularly high in young women ages 15-19, and their risk of suicide is also more than double that of non-pill users. A deregulated stress response is probably part of the picture, but another factor seems to be the low levels of the neuropteroid allopregnanolone – a degraded progesterone product that acts as a natural sedative. In women taking pills, research suggests, levels are significantly lower than in women who use natural cycling. Women who start the pill should keep a mood journal or ask a friend to keep an eye on them, especially if they have a personal or family history of mood-related symptoms. For young women, the pill may not be worth it if it is being used for reasons other than pregnancy prevention – for example, to clear acne or regulate periods.
What size effects are you talking about?
They are relatively small. But on an individual level, some women experience major changes, while others have absolutely none. Every woman should know about the research out there so they can monitor themselves and solve problems.
There are over 100 different pill formulations, plus several other hormonal birth control options. Should we treat them the same?
The signage will be different. Progestins are divided into four different generations, each with a somewhat different molecular structure. Each tablet may also have a different proportion of progesterone and artificial estrogen. At the moment, existing research rarely divides women based on the type of progestin they are in, let alone the proportions. We need to put pressure on science to start looking at this.
Should women look for alternatives to the pill?
I am not making recommendations to any woman individually. Each one knows what their life goals are and how their body feels. But I advise women to be strategic in using the pill. Understand the psychological compensations and then decide whether or not to use them. For many women, the answer will still be yes, but now they choose to know this information. With all the different formulations available, I am confident that women who want to use the pill can find one that works for them. For women looking for something that has no hormones, the copper IUD is one of the safest.
Are you concerned that raising these questions may turn women into less effective birth control methods that may leave them with unwanted pregnancies?
It's the last thing I want to happen. I hope we can use this moment to educate ourselves, but we still recognize how important it is to protect ourselves from unwanted pregnancy. Not being pregnant when you don't want to get pregnant – for me the benefits far outweigh any brain changes that the pill can cause.
You say the issue of birth control is still unresolved. So what would solve that? Better pills, a male pill or something totally new?
Ideally, we want contraception that is really safe and effective that doesn't fit anyone's brain. Perhaps this means more investment in the copper IUD. Or maybe it's still something to be invented. But we need the imagination of the best researchers on this subject. The pill works so well and is so easy that we become complacent. In the meantime, we need more and better research to understand what we have.
• How the Pill Changes Everything: Your Brain in Birth Control is published by Orion (£ 19.99). To request a copy, go to guardianbookshop.com or call 020-3176 3837. Free UK p & p over £ 15, online orders only. Phone orders min p & p from £ 1.99