Hormonal Birth Control Affects Libido Differently When You're In A Relationship, New Study Finds

Ever wondered how your choice of hormonal contraception might be affecting your sex drive? A new study out of Norway has provided some intriguing answers — and the results are tied to the specific hormones involved in female birth control, which seems to influence our sexual behaviors in interesting ways. But it's not all about hormones. It also appears that our libido and our hormones, artificial or otherwise, are tied into another concern: how committed we are in a monogamous relationship, or whether we're out exploring options on Tinder and playing the proverbial field.

Links between contraceptive methods and female libido have been known for quite some time, though they're not as widespread as you might think; it's not actually common to have either a massive peak or a total trough after starting on a new type of no-baby mechanism. A review of 33 years of studies found that 22 percent reported rises and 15 percent falls in sex drive, but researchers have noted that a lot of what we report about desire is relative: we may believe that it's due to a new Pill, but there may be other complicating factors, as libidos are delicate and sometimes wayward things.

This new study, however, shows a pretty firm link between the type of contraception you choose, what kind of relationship you're in, and how often you're wanting to jump in bed — that is, at least if you're heterosexual. Here's what you need to know about the latest science on how hormonal birth control affects sex drive.

The Key Is In Your Pill — And Your Commitment

The study, which was done in partnership with the University of New Mexico, studied 387 women, all of whom were in heterosexual relationships, and wanted to see if there was a relationship between their type of contraception, the committed nature of their relationship, and the frequency of their sexual life. It turns out that how women desire sex, and what they do about it, is at least partially mediated by the kind of contraception they're taking.

The researchers found that women who were taking contraception heavy on the estrogen and lighter on the progesterone (the combined pill is the main example) were more likely to desire sex in "less committed" relationships, while ones taking contraception that emphasized progesterone (the mini-pill, for instance, or implants) had higher sex drives in committed partnerships with long-term partners.

It was a fascinating result, because the researchers were actually looking for a decent reason for humanity's interest in sex outside of the whole getting-pregnant thing; we're one of the only animal species that has sex outside of a purely procreative context, when there's little to no chance of anybody getting pregnant (particularly with the addition of contraceptives). Non-procreative sex that has nothing to do with fertilization has been observed in only a few other species, like bonobo apes, and we're still trying to figure out why.

The Norwegian scientists think this interaction with hormones might give us a clue: it may be about pair bonding, because the more committed we are, the more likely we are to have progesterone-fuelled sex. And, as we'll talk about next, that's sex that's deeply unlikely to get us pregnant.

Why Progesterone & Estrogen Influence Libido In Different Ways

There's a reason the scientists looked at estrogen and progesterone imitators in contraceptives. They're associated with very different parts of the female cycle, and one is much more associated with ovulation and pregnancy than the other.

If you remember health class in school, you'll remember that estrogen is associated with the lead-up to ovulation: the production of estrogen stimulates the body's thickening of the uterine lining to help support fertilized eggs, and creates cervical mucus to help the journey of sperm. Ain't nothing gonna help a baby like estrogen. Progesterone, meanwhile, peaks in the body after ovulation, maintaining the thickness of the uterine lining just in case an egg implants in it. Differing methods of contraception approximating the effects of these hormones emphasize different bits of the menstrual cycle to stop the body getting knocked up. Let's all take a minute to appreciate modern medicine.

The Norwegian scientists zeroed in on an intriguing part of this: a previous study in 2013 had indicated that women on no birth control who were in committed relationships tended to want more sex with their partners during the progesterone "phase," when they had little chance of actually getting pregnant. In other words, the more "loyalty and faithfulness" you showed in your relationship, the more likely you were to want to get busy while not actually having much chance of getting knocked up. Non-procreative sex in the progesterone "phase" of the menstrual cycle seems to be about commitment and bonding, not just rampant lust.

And the new 375-woman study backs this up. Women were most sexually active in two scenarios: if they were on estrogen-heavy contraception, they wanted sex more in casual relationships, while if they were on progesterone-heavy ones, they peaked in committed relationships. This adds a new chapter to what we already know: scientists have identified that the drop in estrogen in menopause seems to play a role in lowered libido, though testosterone drops are likely more important. And estrogen and synthetic progesterone are known to mess with the sex drives of some women; but this is the first study where libido has been looked at through the twin lens of the type of contraception and the commitment of their relationships. This discovery might help us understand why some women's libidos flatline and others do not.

What This Means For You

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So what does this mean in a practical sense? If you've been feeling your desire dip in your long-term relationship, even though you're incredibly committed, a shift to a progesterone birth control might help an uptick; and an estrogen-based contraceptive might spur your sex drive when you're playing the field.

But it's still an open and intriguing bit of study; we're not sure whether the notion extends to gay women who take birth control for health reasons, for instance. A study in 2014 found that same-sex intimacy may have an evolutionary basis in bonding and keeping relationships and friendships strong, much like the non-procreative sex in this study. Whatever the case, it seems pretty clear that there are good reasons for us to continue to get busy —even if there's no baby on the horizon.

Images: Ashley Batz/Bustle; Giphy