Yes, birth control can affect who you are attracted to.

To say this is absurd means knowing nothing about hormones.

If you’ve ever had to suffer through an awkward middle school health class, there’s a good chance that you’ve probably heard about all the stuff that estrogen does from the neck down to promote reproduction. A little follicle stimulation here and a little endometrial lining proliferation there. However, there’s a piece of the puzzle you probably haven’t heard much about that is just as important to the process of reproduction as is the release of an egg: sex. And sex requires a partner. So, estrogen – in addition to all of the things that it does to make conception possible – may also have a hand in partner choice. And there’s a growing body of research in psychology that suggests that this is exactly what goes on.

Research conducted on heterosexual women finds that, as estrogen increases across the cycle, so too does women’s sexual desire and interest in cues of good genetic quality in men. In particular, this research finds that estrogen increases women’s preference for men whose faces, voices, and behaviors exhibit cues to the presence of relatively high levels of the male sex hormone, testosterone (we’re talking square jaws, deep voices, and swagger). This research also finds that estrogen tends to heighten women’s preference for the scent of men who possess testosterone markers and whose faces and bodies are symmetrical. Estrogen increases attention to these qualities (and makes them more desirable to women) since each of these cues are reasoned to be indicators of high genetic quality in men, which is something that would have led to more successful pregnancies and more surviving children.

So what happens to women when they go on birth control? And their levels of estrogen are kept very low. Does this suppress their preference for testosterone in men? And by doing this, does the pill affect who women are attracted to?

Given everything that estrogen does to impact women’s desire for sex and partner choice, it probably shouldn’t be hugely surprising that the pill can have some pretty sweeping effects on women’s sexual and mating psychology. But I still find this research shocking. It finds that, in addition to predicting decreased sexual enjoyment and increased risk of sexual dysfunction, the birth control pill may also affect who women are attracted to…and so so in ways that may have implications for their relationships in the long-term.

For example, in one study that was conducted on a sample of 55 women, researchers had women use a special computer program to manipulate the appearance of photographs of male and female faces. Clicking on a computer mouse allowed them to masculinize or feminize the facial prototype, which they were asked to manipulate to look like their ideal short-term or long-term romantic partner. After their first laboratory session, half of the women in their study started taking the birth control pill and the other half did not. Both groups of women came back to the lab three months later and completed this task a second time.

When the researchers compared the two sets of images created by the non pill-takers, they found no differences between the faces they created at time one and time two. However, for the women who started the pill, they found that women’s ideal male faces became significantly less masculine after the fact. A follow-up study of pill-taking women’s actual partner choice echoed these results. Using a sample of 170 age-matched, partnered women, researchers found that the faces of men who were chosen as partners by women who were on the birth control pill had significantly less masculine faces than those of their non pill-taking contemporaries.

These differences can potentially have important implications for women’s relationship satisfaction. For example, in one study conducted on 2,519 women, researchers compared ratings of relationship quality given by women who had chosen their partners when they were on the pill to those given by women who had chosen their partners when they were not on the pill. They found that women who had chosen their partners when they were on the pill reported less sexual attraction to their partners, less sexual arousal in response to their partners, and less sexual adventurousness than women who had chosen their partners when they were not on the pill. Later longitudinal studies found similar patterns. After following two samples of married couples (one sample was comprised of 48 couples; the other 70 couples) for up to five years, they found that women who chose their partners when they were on the pill and then went off of it experienced changes in sexual and relationship satisfaction in response to their change in hormonal status. Specifically, they found that all of these women reported decreased sexual satisfaction after going off the pill. And for women who were paired to unattractive husbands? They found that this change was accompanied by a decrease in overall marital satisfaction.

The results of these studies suggest that the pill – by influencing who women are attracted to – may have important implications for women’s relationships. Given that pill-taking women don’t exhibit the preference for cues to testosterone are observed in naturally cycling women, there’s a chance that a partner chosen on the pill – when women prefer rounder, more feminine faces than what is observed in non-pill-takers – may not meet a woman’s masculinity standards once she goes off the pill.

As unsettling as this interpretation may be, it is consistent with what research tells us about the effects of estrogen on mate preferences. It is also consistent with stories that I have heard from women about their transition off of the birth control pill. Although many women are able to transition off of the pill without having any major relationship disruptions, this isn’t true for others. As a research psychologist, I have had the opportunity to collect data – both in the form of surveys and interviews with women – about their experiences on and off of the birth control pill. In the process, I have spoken to several women who have had no issues with their partners whatsoever in their transition on and off the birth control pill, but also many for whom it proved very disruptive. In some, it was disruptive because they found that being off of it decreased their attraction to their partner. In others, it increased their attraction to other men. In others yet, it did both. In many of these cases, the relationship with their partners ultimately ended, which is a heartbreaking thing to have happen in response to changes in a medication.

The idea that your birth control pill might influence your choice of relationship partners in a way that that could mean trouble down the road might sound a little scary. But take heart in knowing that this doesn’t happen to all women. It’s also worth keeping in mind that relationships are always scary. The pill just adds a new wrinkle into the mix. And there is a lot that we still need to know. For example, are all birth control pills equally likely to have an impact on partner choice? And how doesthe pill impact the partner preferences and choices of women in LGBTQI+ relationships? Although there is every reason to believe that the impact of the pill on the brain should operate very similarly across people, regardless of sexual identity or orientation, we need more research to know for certain whether this is true.

Lastly, it’s worth point out that being on the pill when you choose your partner may increase your risk of some types of relationship problems, but it dramatically decreases your risk of others. For example, being on the pill decreases women’s risk of needing to get married out of financial necessity or because they got pregnant unexpectedly. It also grants women the opportunity to take their time in finding the right partner and allows them to meet their career goals and be less financially dependent on men. Both of these things increase women’s ability to find satisfying relationships. Knowing what the pill does when it comes to choosing men means that you get to choose who you want to be and what you prioritize in your partner. And that’s empowering. Whether you are on the pill or off of it, you get to pick what happens next.