Science of Love, Sex, and Babies

Oxytocin isn’t the only love drug

Posted in news by jenapincott on May 3, 2009

love_drug_sticker-p217913312752479072q0ou_4002In all the media frenzy about the “love drug” oxytocin — a hormone released after sex, when kissing, after twenty seconds of hugging, and so on — we have lost sight of another hormonal cue of closeness and trust: progesterone. Who talks about progesterone outside menopause discussions? In BLONDES I try to give progesterone some credit, discussing it in questions involving movie-watching lovers, female friendship in the luteal phase of the menstrual cycle (after ovulation), and the effect of lactating mothers on the sex lives of their friends.

Progesterone is interesting because it can indicate a person’s motivation to bond with others.

The higher your progesterone levels, the greater your “affiliation motivation” – that is, the satisfaction you derive from positive relationships with others. In women, progesterone levels are higher after ovulation and during pregnancy. Women on oral contraceptives have been found to have higher levels of “affiliation motivation” than men and women who don’t take birth control because the Pill contains progestins. Progesterone may also give oxytocin a boost by increasing the number of oxytocin receptors in the brain. People with high levels of progesterone rate their friends, family, and long-term partners as more attractive than do people with lower levels of the hormone. From an evolutionary perspective, progesterone is one of those hormones that helps you trust, bond with, and identify with others — and even put another person’s well-being above your own.

This theory was put to the test in a hot-off-the-press study led by neuroscientist Stephanie Brown at the University of Michigan. Brown and her colleagues recruited 160 women, paired them up, and assigned each pair to one of two groups. Pairs in Group 1 were told to play a “closeness game,” which involved asking each other questions such as, “What the greatest accomplishment of your life?” Pairs in Group 2 were told to proofread an article together and try to find as many errors as possible. Following this, everyone filled out a test that assessed closeness and — astonishingly — willingness to risk one’s life for the partner. The women then were assigned to play a cooperative card game (the idea is to win by working together). Before and after each exercise, each participant’s saliva sample was collected and progesterone levels tested. One week later, all the women returned to the lab to play the cooperative game again with the same partner they had the first time.

The results? Unsurprisingly, it turned out that the closeness game induced higher progesterone levels. Women who asked each other personal questions not only had higher progesterone levels after the cooperative game, they also reported a stronger willingness to sacrifice their life for their partner. Progesterone levels among those women who played the “closeness game” were also higher when they returned to the lab for the second round of tests a week later.

Progesterone, the researchers say, is hormonal proof of the positive health effects of meaningful social contact. Does high progesterone drive people to sacrifice their own lives for others? As the researchers point out, the hormone is correlated with this behavior; they can’t yet prove that it causes it. Nevertheless, it’s known to reduce stress and enhance bonding behavior — it’s not a stretch to say that high-progesterone types are more loving and giving.

But what does this mean for romantic love? Further research between potential romantic partners would be interesting. Would the progesterone surge following a “closeness game” lead couples to bond more easily, stress less, and sacrifice themselves more readily? Do relationship counselors now have hormonal proof that couples should ask each other prying questions on dates? Will control freaks start testing their date’s saliva for “affiliation motivation”? (Readily available are home test kits to measure progesterone levels.)

Unlike other potential “love drugs,” lovers are advised against taking progesterone supplements as relationship aids. While the hormone is related to trust and bonding and cuddling, and helps prime the sex drive, an excess is associated with a low libido. Love drug, maybe. Lust drug, not.


2 Responses

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  1. Lance Chambers said, on February 27, 2010 at 8:51 pm

    I guess you’re right. Couples should not take progesterone supplements as relationship aids because while it is true that the hormone is related to trust and bonding, relationships should be based on love and is developed and cultivated by couples who are willing to compromise to make their relationship work and it doesn’t always have to do with the hormones.

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