Turns out that if you've ever noticed an unexplained spike in your sex drive, your contraception method could have something to do with it. The birth control you use, when combined with how invested you are in your relationship, could influence how often you're having sex, according to a new study just published in Evolution & Human Behavior.
Researchers in Norway asked 275 straight female college students (all of whom were on hormonal contraception and in relationships) how many times they'd had sex over the preceding week, how invested they were in their relationships, and what kinds of birth control they used. Across the board, they found that women who were more committed to their partners were having more vaginal intercourse with them — not surprising! They also found that women who were committed to their partners and were on birth control with lots of progestin and lower doses of estrogen — the mini-pill is one example — tended to have more sex than women who were committed to their partners and weren't on this type of birth control. The women who used birth control with more estrogen and less progestin, on the other hand, were at their most sexually active when they weren't that committed to their partners.
There's a key difference between estrogen and progestin that could help explain why: Estrogen naturally peaks right before ovulation, while hormones that have the same effect as progestin peak at times of the month when conception isn't possible. Women who aren't super committed to their partners may be less likely to have sex for just the purpose of bonding, and their urge to have sex might be especially strong at times when their bodies are sending signals that it's time to conceive — for example, when they're on BC with lots of estrogen. Of course, this doesn't mean that you should base your choice of birth control method on your level of commitment to your partner — trial and error is still how most people discover which birth control method is right for them, and there are plenty of considerations other than libido.