The dark side of oxytocin, much more than just a “love hormone”

By Ed Yong | November 29, 2010 3:00 pm

MotherThere’s a chemical that can subtly shift your childhood memories of your own mother. In some people, it paints mum in a more saintly light, making them remember her as closer and more caring. In others, the chemical has a darker influence, casting mum as a less caring and more distant parent.

All of this becomes heavily ironic when you consider that the chemical in question – a hormone called oxytocin – is often billed as the “hormone of love”, and even marketed as “Liquid Trust”. As a new study shows, the reality is much more complicated. Describing oxytocin as the “hormone of love” is like describing a computer as a “writing tool” – it does other things too, some of which aren’t pleasant.

Oxytocin is a versatile actor, whose resume includes all sorts of jobs in sex, reproduction, social behaviour and emotions.  It can increase trust among people and make them more cooperative (this works in meerkats, too). It can increase the social skills of autistic people. It’s released during orgasm. It affects lactating breasts, contracting wombs and the behaviour of sheep mothers towards their newly born lambs. The list goes on: drug addiction, generosity, depression, empathy, learning, memory.

Despite these many roles, oxytocin is often reduced to a misleading label. While “hormone of love” may be great for catchy headlines and compelling marketing slogans, they are ultimately misleading. Jennifer Bartz from the Mount Sinai School of Medicine has found that oxytocin can have completely opposite effects on the way people behave, depending on how they view their relationships to other people.

She recruited 31 men* and asked them to sniff either an oxytocin nasal spray or another spray with the same ingredients minus oxytocin – a placebo. A few weeks later, the sprays were swapped so that the men who took oxytocin now took the placebo, and vice versa. At the time, neither the scientists nor the volunteers knew which was which – that was only revealed after the experiment was over.

Before all of this, the men completed a series of widely used questionnaires to measure the state of their social ties. The questions assessed the nature of their bonds with their families and friends, how sensitive they are to rejection, how comfortable they are at being close to other people, how much they desire that closeness, and more. Shortly after using both sprays, the recruits also answered questions about their mother’s parenting style.

Bartz found that when she averaged out the volunteers’ results, the sniffs of oxytocin hadn’t seemed to colour their memories of their mothers. But things changed when she looked at them individually. Those who felt more anxious about their relationships took a dimmer view of their mother’s parenting styles when they sniffed oxytocin, compared to the placebo. Those who were more secure in their relationships reacted in the opposite way – they remembered mum as being closer and more caring when they took the oxytocin.

These results show that oxytocin is far from being a simple “love hormone”. As Bartz says, it has a “more nuanced role… than previously thought,” and one that varies from person to person.  It’s “not an all-purpose attachment panacea.”

For now, Bartz isn’t sure why oxytocin can have such different effects. Her most educated guess is that the hormone triggers a biased trip down memory lane. Under its influence, people are more likely to remember information about their mother that fits with their current attitudes to relationships. If they are anxious, they’re more likely to remember the negative side of their early life. It’s a reasonable enough idea, and one that Bartz intends to test in the future. It will also be good to repeat the study in a larger group – 31 men make for a relatively small study.

But this isn’t the only study to show the subtle side of oxytocin. Just three months ago, I wrote about research from Heejung Kim at the University of California, which showed how oxytocin’s effects vary across different cultures. To fulfil its many roles, oxytocin has to dock at a protein called the ‘oxytocin receptor’, encoded by a gene called OXTR.

Kim found that when Americans who carry a particular version of the OXTR gene are more likely to turn to their friends for support when they are distressed. But Koreans react to social stress in a different way – for them, it’s less socially acceptable to turn to friends for support during tough times. And distressed Koreans who carry the same version of OXTR are less likely to seek support from their friends.

As I wrote then, “In cases where genes affect our behaviour, the same stretch of DNA can lead to very different deeds, depending on individual circumstances. Just as a production defines a play, environments and cultures alter the effects of certain genes.”

*Bartz only worked with men because there are risks involved in injecting women with oxytocin – if she’s pregnant, it could induce labour, and it might affect the foetus in as yet unknown ways.

Reference: PNAS http://dx.doi.org/10.1073/pnas.1012669107

Photo by Ian Riley

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Comments (14)

  1. Adrian Blake

    So after sex I think of my mum differently? Gross! How long do I need to keep my phone off to avoid this?

  2. rdtheta

    Since I enjoy wild speculation about things that aren’t in my field (based on interesting articles on the internets): sounds like oxytocin enhances emotions. I don’t know much about its natural production; is it always around in a person’s system?
    Do doses of it enhance anger? Fear?

  3. Paul Raeburn

    It would have been interesting if Bartz had asked about *both* parents’ parenting styles. (Spoken by a guy writing a book on fathers.) It would have been easy enough; just add another question. Any differences between perceptions of mothers and fathers might have been illuminating. But, as in so much family research, fathers were once again ignored or excluded. (As if fathers don’t have parenting styles…)

  4. Alyson

    How not surprising on one level that a hormone involved in the formation of primary bonds, those that can have serious impacts on your survival, would be discerning. After all, if you had a mother who was dangerous, abusive, etc., how counter productive would it be for you to bond so tightly to her that you were all over her all the time, increasing your chances of pissing her off and killing you. And, how beneficial for you to be more bonded to a mother figure who was good to you, and provided you with nurture.

    After all, bonding or not is ultimately about “what will help me survive.” We are social because it benefits us, and an indiscriminate bonding agent probably would have led its possessors into extinction in the face of “cheaters” a long, long time ago.

  5. Ed,

    Wonderful column. My expertise is the psychology of risk perception, and I have done some reading on oxytocin and trust (not the kind you want to boost in a bar with Liquid Trust – you can the stuff with pheromones – to boost THAT kind of trust). It turns out there is a high concentration of oxytocin receptors on the amygdala, the area of the brain where fear starts. As oxytocin levels go up, the ability of the amygdala to be warry and more mistrustful goes down. I describe this in Ch. 3 of How Risky Is It, Really? Why Our Fears Don’t Always Match the Facts. A few graphs of which are below. I wonder whether the influence of oxytocin on the amygdala might be connected with the finding of the study you write about.

    TRUST

    Humans are social animals. Our individual prospects depend to a significant degree on the prospects of the group(s) to which we belong, and how well we get along with the group(s). Survival means being acutely sensitive to who is on our side and who is not. So it isn’t surprising that trust matters so much to how we go about protecting ourselves. And it isn’t surprising to find the instinct for trust rooted deep in the brain.
    Few forms of trust are more basic than that between a newborn and its mother. Scientists have discovered that this relationship is strengthened by the hormone oxytocin, released when the baby stares up at mom while breast feeding. Staring lovingly at your boyfriend or girlfriend can trigger their release of oxytocin too, as can warm physical contact like touching and hugging. (Levels increase during sex and peak at orgasm, which may help explain the age-old question “But will you love me in the morning, when your oxytocin levels have dropped?”) Oxytocin reduces stress in arguing couples, helps us recognize faces, even helps us look at a face (in fact, just a pair of eyes) and identify the mood that person is in. The stuff is magic.
    Based on the evidence that oxytocin is involved in social bonding, researchers tested its impact on trust.
    A Risk Quiz; Let’s say you are one of the volunteers to whom researchers gave $100, and this option: you can either keep the money, or give it to an anonymous trustee who will either invest it and double it to $200 and return half of the extra hundred bucks to you–$50–or keep all the money for herself. So you can either increase your money by 50%, or lose it all. What would you do? Would you trust that anonymous trustee? (Remember Loss Aversion from Chapter Two, where in a similar experiment most people decided to avoid the gamble and take the sure cash.)
    An hour before the start of this actual experiment, half the volunteers were given a sniff of oxytocin. The other sniffed a placebo. The oxytocin-exposed group was much more trusting. More volunteers who had sniffed the hormone trusted the anonymous investors and gambled with their money.5
    A later experiment by another group took it a step further. This time the volunteers were told how they did, and in half of the cases, they learned that the trustee had burned them and kept the money. The volunteers who were burned were asked whether they wanted to try again. What would you do? This would be like getting that spam from the Nigerian Prince a second time and sending him $5,000 again, right?
    Half the group of burned volunteers got a whiff of Eau de Oxytocin, half got a sniff of Eau de Placebo. Those who sniffed the oxytocin were more trusting and ready to invest with an anonymous trustee a second time than were the placebo-exposed subjects. And when they were asked “Do you want to try this again?” the oxytocin-treated volunteers responded more quickly than the volunteers who hadn’t gotten the nose full of Trust Spray.6
    Like I said, it’s amazing stuff. And it shouldn’t come as a surprise that it affects that amazing part of your brain so intimately involved in keeping you safe…the amygdala. Remember, trust has a lot to do with survival among social animals who depend on each other for safety and protection. Show someone an untrustworthy face, and the amygdala is one of two areas that become more active than anywhere else in the brain.7 It is apparently programmed for reading trust just as it is for snakes or spiders.
    But we have to be just as good at recognizing who we can trust, so the system needs fine-tuned control. That’s apparently where oxytocin comes in. The amygdala, that critical organ for our biological risk response, has a high concentration of receptors for oxytocin. In the second set of those gambling experiments with the volunteers and the trustees, researchers used fMRI to watch the brains of the volunteers as they made their choices. As the levels of oxytocin in the brain went up compared with the placebo group, activity in the amygdala went down! Oxytocin diminishes the amygdala’s ability to send out the message “Warning! Warning! I don’t trust this guy.”
    These fundamental biological underpinnings deep in the self-preservation systems of the brain suggest why trust plays such a powerful part in our risk response. As we learned from how the public reacted to the way the governments in Japan and Germany handled the outbreak of Mad Cow disease.

  6. Oxytocin production does not exist separately from the evolved neurophysiological mechanisms that regulate gonadotropin releasing hormone (GnRH) pulsatility. There are mammalian pheromones that are known to directly influence the GnRH pulse, for example androstenol. Oxytocin is not considered to be a pheromone by anyone I know who is involved in olfactory research. Sniffing it is simply a delivery method that we now can see might have negative consequences.

  7. jld

    @david ropeik

    Your whole comment goes against the very content of the blog post and is just a rehash of the “classic” view of oxytocin without anything new whatsoever.
    Please explain, are you a PR employee of some vendor?

  8. May the increased violence in recent years be reduced by inducing oxytocin and orexin (hypocretins) on those belligerent and bellicose?

  9. neil o'c

    haven’t read the study but initial thoughts are – no way is that a big enough sample to perform a subgroup analysis. I assume thats what they did? Were the analyses established a priori? Could another interpretation be that oxytocin had no effect? Happy to be wrong!

  10. @Neil O’c – No, not subgroup analyses, they did a regression. It certainly looks like the hypotheses were established beforehand – after all, why measure the state of their social ties if all you want to do is to look at effect of oxytocin on memories of mum? I’d agree that the sample size is on the small size though. It needs replication.

  11. neil o'c

    Cheers Ed – that’ll teach me not to go read the paper. Interesting findings

  12. Gerald Summers

    Based on the article and comments, Oxytocin seems to produce symptoms similar to marijuana, enhancing whatever feelings one has at the time. If you are feeling mellow, you will continue to do so. If you are nervous, you might start feeling paranoid.

  13. surgeek

    Good points #3. Paul Raeburn and #4. Alysons.
    This mother-child bonding is the most glorified myth that is not re-thought as often as it should. Its apparant purpose is just to make a dangerously selfish mother (such frustrated mothers do exist a lot more than we read in the news) to think twice before harming her defenseless child which is oftentimes in her sole custody in our society. Acts of such mothers are branded as mental illness rather than plain cruelty. While most people (men and women alike) tend to protect, and not harm a child, the real bonding can happen beetween two independent, mature adults.
    Also, a lot of responsible and caring fathers’ work is seldom given credit for in most societies.
    Studies like this – with narrow focus and based on non-scietific generalizations of human behaviors – are just for getting publications for the researchers conducting it, to keep the grant flowing.

  14. Hey there! Do you know if they make any plugins to help with Search Engine Optimization? I’m trying to get my blog to rank for some targeted keywords but I’m not seeing very good results. If you know of any please share. Appreciate it!

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