Does Oxytocin Make Us Fall in Love?

couple kissing on carousel — Oxytocin has a role in bonding us to our social and sexual partners, but it’s not a magic bullet. Igor Ustynskyy/Getty Images

For $50, you can go online and buy a 60-milliliter bottle of nasal spray containing oxytocin, a naturally occurring hormone produced in the human brain.

Since the spray isn't approved by the U.S. Food and Drug Administration, it can't be sold as a cure or treatment for anything in particular. But if you've followed the headlines over the past decade, you know that oxytocin — the hormone chiefly responsible for triggering contractions in pregnant women and letting down milk during lactation — has also been shown to enhance feelings of social bonding and improve sociability in people with autism.

As the manufacturers of the nasal spray promise: "You will no longer get tired of social interactions, rather you gain an ability to enjoy them. You will be able to read emotions off people's faces, look at others in the eye without flinching in an empathetic way."

Empathy and eye contact are great and all, but oxytocin also has a sexier side. Oxytocin levels have been shown to spike during orgasm, and people dosed with extra oxytocin have warmer, fuzzier feelings toward their spouses and partners. New lovers also have higher natural oxytocin levels than their single peers. All of which has earned oxytocin the catchy nickname, the "love hormone."

But while decades of research have proven that oxytocin clearly has a role in bonding us to our social and sexual partners, it's not a magic bullet — or magic nasal spritz — to achieve romantic bliss. Experts warn that there's still plenty to learn about the popular neuropeptide, and that oxytocin is likely not the only ingredient in the complex biochemical soup we call love.

Which Came First, the Hormone or the Happiness?

Dr. Bradley Anawalt is chief of medicine at the University of Washington Medical Center and board-certified in endocrinology (a hormone specialist). He's had a front row seat as scientists have uncovered oxytocin's curious effects on brain chemistry and human behavior.

Anawalt cites studies showing that doses of intranasal oxytocin light up the same reward centers in the brain as sexual arousal, chocolate cake and drugs like cocaine. That people treated with oxytocin are more attracted to images of faces that resemble their spouse. And that men in relationships will stand farther back from an attractive stranger when under the influence of extra oxytocin.

But Anawalt says it's important to distinguish that in most of these studies, the administration of oxytocin nasal spray doesn't make the recipient "fall in love" with anyone. It's more accurate to say that the extra dose of the hormone "enhances our emotional reaction" to people with whom we are already romantically or socially bonded.

Anawalt points to the study in which men in committed relationships treated with oxytocin preferred to stand farther away from an attractive research assistant compared to those treated with placebo. The study authors concluded that oxytocin might play a role in promoting monogamy in men. For Anawalt, the question is whether the oxytocin influences monogamy by enhancing sexual attraction or by reinforcing social expectations.

"If I'm bonded to a female partner, that means I love that person or I'm strongly attracted to her, and my feelings for that person are accentuated by the oxytocin and therefore I respond differently to her than to other women," says Anawalt. "That's one plausible explanation."

"Another explanation is that oxytocin is simply reinforcing a social relationship I have with somebody. I'm supposed to be with my female partner and I'm not supposed to be with this other woman."

I'll Read What She's Reading

Oxytocin is a neurotransmitter and hormone that is produced by the hypothalamus in the brain. It is released during sex, breastfeeding and childbirth, all activities that have to do with bonding. It could be nature's way of promoting families by reinforcing positive feelings with people we are already physically close to.

Researchers have tested natural oxytocin levels in the blood of both men and women before, during and after sexual activities, and oxytocin levels go up as arousal increases.

During orgasm, oxytocin likely plays a similar role that it does in childbirth. Upon orgasm, a flood of oxytocin into the bloodstream triggers smooth muscle contractions in the uterus and pelvic muscles.

Anawalt mentions that body massage has also been shown to increase natural oxytocin levels in the bloodstream, another sign that physical pleasure is mediated by oxytocin in some way. But he's quick to point out that oxytocin is more than just another "O" word.

"The flipside of this is that reading a good book also increases oxytocin," says Anawalt. "It may be that a relaxed state or a general state of pleasure is associated with high oxytocin levels."

When Bonding Goes Bad

There are a number of interesting findings indicating that oxytocin alone isn't enough to produce happily bonded relationships. The effect oxytocin has depends on the overall quality of our existing relationships.

A 2010 study, for example, administered oxytocin or placebo to a group of men and asked each of them to describe their mother's parenting style. You might expect that men who received oxytocin would have warmer recollections about their moms, but that was only true with men who also described their current relationships as healthy and happy. Men who were more "anxiously attached" in their current relationships described their mothers as less caring on oxytocin than just placebo.

Another study showed that doses of oxytocin increase in-group favoritism and the exclusion of others. The researchers concluded that the close social bonds enhanced by oxytocin come at a cost to outsiders, who are viewed as even less trustworthy. Follow-up studies found similar associations between oxytocin and negative emotions like envy, distrust, favoritism and schadenfreude.

This reinforces the belief that oxytocin appears to function as an emotional enhancer, and not, as one of the study authors put it, "an all-purpose attachment panacea."