Hormonal birth control does appear to nudge certain attraction-related preferences, but the effects are subtler, less consistent, and more contested than the alarming headlines suggest. The best-studied shifts involve body-scent preferences tied to immune-system genes and, possibly, preferences for certain facial features. Yet several large replication studies have failed to confirm some of the splashiest early findings, leaving researchers genuinely divided on how much any of this matters for real-world relationships.
The Scent Shift and Immune-System Genes
The most widely cited evidence comes from research on the major histocompatibility complex, a cluster of immune-system genes often called MHC. In many species, females tend to prefer the scent of males whose MHC genes differ from their own. The evolutionary logic is straightforward: offspring with a more diverse set of immune genes may be better equipped to fight off parasites and infections. Work in salmon, for instance, has shown that MHC-dissimilar pairings produce offspring with greater parasite resistance, and that wild fish naturally mate in ways that maximize this diversity.
1PubMed Central. MHC-mediated mate choice increases parasite resistance in salmonHumans seem to show a version of this preference too, at least in controlled sniff-test experiments. But a key study found that women using oral contraceptives shifted their scent preferences toward MHC similarity rather than the usual dissimilarity. Women in a control group who were not on the pill showed no such shift.
2PubMed Central. MHC-correlated odour preferences in humans and the use of oral contraceptivesThat finding got a lot of attention because it suggested hormonal contraception could steer women toward genetically similar partners, potentially undermining one of the body’s built-in mate-screening tools. It’s worth noting, though, that sniff tests in a lab are a long way from choosing a life partner. Whether this preference reversal meaningfully shapes who someone actually dates or marries is still an open question. Nobody has run the definitive study tracking MHC-based partner choice in pill users versus non-users over the course of real relationships.
Facial Masculinity Preferences
Another line of research asked whether the pill changes what kinds of faces women find attractive. An early experimental study found that women who started using oral contraceptives between two testing sessions showed a decreased preference for masculine male faces. The same study looked at real-world partners and reported that women who were on the pill when they chose their partner tended to end up with less facially masculine men compared to women who were cycling naturally at the time.
3PubMed. Oral contraceptive use in women changes preferences for male facial masculinity and is associated with partner facial masculinityThis became one of the most-discussed findings in the field. But when larger, more rigorous studies tried to replicate it, the effect vanished. A well-powered study published in Psychological Science found no evidence that oral contraceptive use decreased preferences for facial masculinity, using both within-person and between-group comparisons.
4PubMed Central. No Compelling Evidence that Preferences for Facial Masculinity Track Changes in Women’s Hormonal StatusA separate large study reached a similar conclusion: women using oral contraceptives showed no weaker preference for masculine characteristics in men’s faces compared to non-users. The only difference the researchers detected was that pill users showed a slightly stronger preference for femininity when rating other women’s faces, which is a different phenomenon entirely.
5PLOS ONE. No evidence that women using oral contraceptives have weaker preferences for masculine characteristics in men’s facesThis is a pattern worth flagging: early, smaller studies in this area produced attention-grabbing results, and then larger replications with better statistical power came up empty. That doesn’t prove the effect doesn’t exist at all, but it does mean the masculinity-preference story is far less solid than it was once presented as being.
What Happens in the Brain
Brain-imaging studies have added another layer to this question, though the findings are preliminary and the sample sizes are small by modern standards. One study found that women on oral contraceptives showed stronger neural responses to faces in the fusiform face area, a brain region specialized for processing faces. The response in this region also increased with the duration of pill use, and the pattern replicated in an independent sample of adolescent girls.
6PubMed Central. Hormonal contraceptives, menstrual cycle and brain response to facesA more provocative finding involved oxytocin, a hormone closely linked to bonding and trust. When researchers administered oxytocin nasally and then showed women photos of their romantic partner, naturally cycling women showed a strong reward-system response in brain regions associated with pleasure and motivation. Women on hormonal contraceptives showed a significantly weaker version of that response. In fact, the oxytocin-induced boost in reward-region activity when viewing a partner’s face was substantially dampened in pill users compared to both naturally cycling women and, in a separate comparison, men.
7Social Cognitive and Affective Neuroscience. Hormonal contraceptives suppress oxytocin-induced brain reward responses to the partner’s faceThis is the kind of finding that sounds dramatic but needs careful interpretation. It’s a single study with a modest sample, and the task involved nasal oxytocin administration rather than natural oxytocin fluctuations. Still, it raises genuinely interesting questions about whether hormonal contraception changes how the brain processes bonding signals, not just abstract face preferences.
Relationship Satisfaction and the Congruency Debate
If the pill shifts attraction at all, the more practical question for most people is whether it actually affects relationship outcomes. A few studies have tried to answer this by surveying women about their contraceptive history and their satisfaction with their partners.
One widely cited study found a complicated tradeoff. Women who were using oral contraceptives when they met their partner reported lower sexual satisfaction and lower physical attraction to that partner over time. They were also more likely to be the one who initiated a breakup if the relationship ended. But those same women reported being more satisfied with their partner’s financial and emotional support and, on balance, stayed in their relationships longer.
8PubMed Central. Relationship satisfaction and outcome in women who meet their partner while using oral contraceptionThat finding gave rise to what’s sometimes called the “congruency hypothesis”: the idea that what matters most is whether your hormonal state when you chose your partner matches your hormonal state later. If you met your partner while on the pill and then stopped, the mismatch could lead to dissatisfaction, because the hormonal environment that shaped your initial attraction is gone. One study found that congruency between past and current contraceptive use predicted sexual satisfaction, even after controlling for relationship length, age, and other factors.
9PubMed. Partner choice, relationship satisfaction, and oral contraception: the congruency hypothesisAnother study drilled into what happens when women discontinue hormonal contraception after forming a relationship. It found that stopping the pill was associated with lower marital satisfaction, but only if the woman’s husband had a relatively less attractive face. If the husband was more facially attractive, stopping the pill was actually associated with higher satisfaction. The interpretation is speculative but interesting: perhaps the hormonal shift after stopping revealed an underlying level of physical attraction that had been partly masked.
10PubMed Central. The association between discontinuing hormonal contraceptives and wives’ marital satisfaction depends on husbands’ facial attractivenessHere’s where the story gets genuinely messy, though. A large Finnish replication study with nearly a thousand women and very high statistical power found no support for the congruency hypothesis at all. The researchers suggested that the effects seen in earlier, smaller studies may have been artifacts of unequal group compositions rather than real hormonal effects.
11Evolution and Human Behavior. A high-powered replication study finds no effect of starting or stopping hormonal contraceptive use on relationship qualityThis is a genuine scientific disagreement, not a case where one side is obviously right. The earlier studies were smaller but used within-person designs that have their own strengths. The Finnish study was far larger but relied on retrospective self-report, which has its own problems. Researchers are still sorting this out, and anyone who tells you the question is settled in either direction is overstating the evidence.
Sexual Desire and Partner Investment
Beyond attraction preferences, some research has looked at how hormonal contraceptive use during partner selection relates to sexual desire down the road. One study followed women into pregnancy and found that those who had met their partner while using hormonal contraception reported higher levels of sexual desire for that partner during pregnancy compared to women who had been cycling naturally when the relationship began. Desire for people outside the relationship did not differ between the two groups.
12PubMed Central. Hormonal Contraceptive Use During Relationship Formation and Sexual Desire During PregnancyThat might sound like it contradicts the finding about lower sexual satisfaction in pill-using women. But the studies measured different things at different timepoints: one asked about overall sexual satisfaction in long-term relationships, while the other specifically measured desire during pregnancy, a period when hormonal states change dramatically regardless of contraceptive history. Both can be true simultaneously, because desire and satisfaction are not the same construct, and both are shaped by dozens of variables beyond contraceptive history.
A separate study using a standardized mate-preference inventory found that women not using the pill scored higher on mate-preference measures during the fertile phase of their cycle than pill users did. This aligns with the general idea that naturally cycling women experience more pronounced fluctuations in what they find attractive at different points in their cycle, while pill users experience a flatter pattern.
13PubMed. Assessment of the relationship between the use of birth control pill and the characteristics of mate selectionWhy the Evidence Is So Hard to Pin Down
Several features of this research area make it unusually difficult to draw firm conclusions. First, “the pill” is not one drug. Oral contraceptives vary in their progestin type, estrogen dose, and cycle regimen, and different formulations could plausibly have different effects on attraction. Most studies either lump all pill types together or don’t report which formulations participants were using, which makes it hard to know whether conflicting results reflect real differences in the drugs being studied.
Second, many of the key studies are cross-sectional, meaning they compare pill users and non-users at a single point in time. Women who choose to use hormonal contraception may already differ from those who don’t in ways that affect their relationships and preferences. They might be at different life stages, differ in their attitudes toward sexuality, or be in different types of relationships. Disentangling the effects of the pill itself from these pre-existing differences is extremely difficult without randomized controlled trials, which for obvious ethical and practical reasons are almost never done in this area.
Third, sample sizes in many of the foundational studies were small. The scent study, the facial-masculinity study, and some of the satisfaction studies all involved fewer than 200 participants, sometimes far fewer. Small samples are prone to producing dramatic-looking results that don’t hold up when tested in larger groups, which is exactly what happened with the facial-masculinity findings.
What Your Doctor Probably Isn’t Mentioning
Regardless of where the science ultimately lands on attraction shifts, there’s a practical communication gap worth knowing about. A survey of women using hormonal contraception found that the vast majority, about 83%, said their healthcare provider never mentioned the possibility of psychological side effects during contraceptive counseling.
14PubMed Central. Psychological side effects of hormonal contraception: a disconnect between patients and providersPsychological side effects in this context include changes in mood, libido, and overall well-being, all of which could indirectly affect how you experience attraction and relationships even if the pill isn’t directly rewiring your mate-preference circuits. If you’ve noticed changes in who or what you find appealing after starting or stopping hormonal contraception, that experience is not unusual and it’s not imaginary. But it also doesn’t mean the pill “tricked” you into choosing the wrong partner, which is how this research sometimes gets spun in popular media.
The honest state of the science is that hormonal contraception probably does have some influence on attraction-related processes, particularly scent preferences and possibly reward-system processing. Whether those influences are strong enough to meaningfully shape partner choice in the real world, where attraction is influenced by personality, shared experience, social context, proximity, and countless other factors, remains genuinely uncertain. If you’re weighing a decision about starting or stopping hormonal contraception, changes in attraction should be on your radar as a possibility, but they shouldn’t be the factor that drives the decision.
Non-Pill Hormonal Methods
Nearly all of the research discussed so far focuses on combined oral contraceptives, the standard “pill.” Much less is known about whether other hormonal methods like the hormonal IUD, the implant, the patch, or the injection produce similar shifts. These methods use different hormones, deliver them through different routes, and produce different blood-level profiles. The hormonal IUD, for example, releases progestin locally in the uterus and results in much lower systemic hormone levels than the pill. Whether that’s enough to influence brain-level processes like scent perception or reward-system responses is simply unstudied in any rigorous way.
Some researchers have used the umbrella term “hormonal contraception” in their studies without distinguishing between methods, which muddies the picture further. When a study reports that “hormonal contraceptive users” showed a particular pattern, it’s usually dominated by pill users because the pill is the most common method in research populations. Assuming those findings extend to every hormonal method is a leap the data don’t support. If you’re using a progestin-only method or a low-dose hormonal IUD, the research that exists may not apply to your situation at all.
Cross-Cultural Variation
Most of the landmark studies in this area were conducted in Western, industrialized countries with relatively homogeneous participant pools, often university students. A large cross-national analysis spanning over 50 countries found that the relationship between hormonal contraceptive use and relationship outcomes varied substantially from country to country.
15Scientific Reports. Hormonal contraceptive use is associated with love intensity across 51 countriesThat variation matters because cultural norms around partner selection, the role of physical attraction in mate choice, and the social meaning of contraceptive use differ widely. In settings where marriages are arranged or where partner choice is heavily influenced by family and community input, any hormonal effect on individual attraction preferences would be filtered through an entirely different decision-making process. The implicit assumption in much of this research, that women are freely choosing partners based primarily on physical and chemical cues, reflects a particular cultural model that doesn’t apply everywhere. Findings from university labs in the UK or Germany may tell us something real about hormonal effects on perception, but how much those perceptual shifts actually matter for partner choice depends on a social context the lab can’t replicate.