Noli Irritare Leones

It’s actually my mother, not me, who is the oxytocin expert, so, Mom, if you happen to read this on Facebook and see that I get anything wrong, feel free to let me know in Facebook comments. But destinyinprogress, at Alexandria, asked me a question about oxytocin in reply to one of my posts, so, here is what I know, and my thoughts about what I’ve read.

My mother did research on oxytoxin, when I was a teenager, and wrote articles with titles like Oxytocin analogs with oxygen-containing side chains in position 3.

From dinner table conversation when I was young, I learned a few basic facts:

Oxytocin is closely chemically related to vasopressin, a chemical that controls reabsorption in the kidneys. There is an illness called diabetes insipidus, much rarer than the usual diabetes mellitus that’s related to blood sugar and insulin. In diabetes insipidus, you lack sufficient vasopressin, and the result is, as with diabetes mellitus, excess urination, fluid intake, and thirst (but lacking a bunch of the other diabetes mellitus symptoms that get caused by blood sugar being out of whack).

Oxytocin is important to contractions of the uterus during childbirth (Pitocin, which is used to induce labor if it’s not happening naturally, is basically an oxytocin injection) and to milk letdown. I can remember visiting my mother’s lab and helping monitor a bunch of female rats who had been given oxytocin, and whose uterine contractions were being measured.

More recently, though, oxytocin has been in the popular press for reasons that have nothing to do with its ability to induce labor, and you can readily find articles describing “the cuddle hormone,” that promotes human attachment and bonding. This “cuddle hormone” is reportedly released during orgasm (which makes a certain intuitive sense, given that orgasm both involves muscle contractions and, for a lot of us, some pretty strong bonding). Some articles further relate that men and women respond differently to oxytocin, in pretty much the way gender stereotypes would lead you to expect, so that women, in particular, tend to produce and respond to oxytocin with orgasm, and so we, naturally, fall in love when we have sex, while all you men are even so much more able to detach sex from love.

The problem is that this description, the full one, I mean, in which oxytocin is both clearly the reason people tend to fall in love when they have sex and clearly works differently in men and women, seems to be a stretch, an overly confident interpretation of research which is relatively new, sometimes contradictory, and which may not always say what the articles indicate. (In fairness, my own knowledge is pretty sketchy, too, on just this point, so I also could get things wrong here.) Here is what Wikipedia has to say about oxytocin:

The relationship between oxytocin and human sexual response is unclear. At least two non-controlled studies have found increases in plasma oxytocin at orgasm – in both men and women.[5][6] Plasma oxytocin levels are notably increased around the time of self stimulated orgasm and are still higher than baseline when measured 5 minutes after self arousal.[5] The authors of one of these studies speculated that oxytocin’s effects on muscle contractibility may facilitate sperm and egg transport.[5] In a study that measured oxytocin serum levels in women before and after sexual stimulation the author suggests that oxytocin serves an important role in sexual arousal. This study found that that genital tract stimulation resulted in increased oxytocin immediately after orgasm.[7] Another study that reports increases of oxytocin during sexual arousal states that it could be in response to nipple/areola, genital, and/or genital tract stimulation as confirmed in other mammals.[8] Murphy et al. (1987), studying men, found that oxytocin levels were raised throughout sexual arousal and there was no acute increase at orgasm.[9] A more recent study of men found an increase in plasma oxytocin immediately after orgasm, but only in a portion of their sample that did not reach statistical significance. The authors noted that these changes “may simply reflect contractile properties on reproductive tissue.”[10]

I reference Wikipedia not because I consider it an absolutely reliable source here; being open to editing by absolutely anyone, regardless of level of expertise, leaves it vulnerable to error (and sometimes worse – just today, some charming soul edited the Martin Luther King entry to use the word “nigger,” though the edit was soon fixed). One of the women in my Quaker meeting, who teaches at a local college, likes to use Wikipedia in her classes as an example of the limits of crowd sourcing in providing accurate information, and she bent my ear, during social time after one meeting for worship, with an account of the errors she’d found on topics where she had some knowledge. I wouldn’t recommend you use Wikipedia as a source if you’re writing an academic paper, even an undergraduate one, about oxytocin. Still, if crowd sourcing isn’t as good as peer review, it does make for an entry a little more neutral than some other popular accounts, a lot of which seem to have a culture wars axe to grind in what they say about oxytocin and sex. And what I get from the Wikipedia entry is that there’s a lot that still isn’t clear, too much to draw any particular conclusions about whether oxytocin does or doesn’t account for differences in men’s and women’s sexual attitudes and behavior.

I should be clear that I’m not saying that oxytocin isn’t released at orgasm, or that it doesn’t lead to bonding and increased trust, or even that women might not, to some degree or other, on average, either release more and respond more readily to said oxytocin, at the point of orgasm. What I’m saying is that the research just doesn’t seem to be all that clear yet.

Our own intuitive individual experiences can’t necessarily tell us that much, about the oxytocin/orgasm/bonding connection. Just because you, personally, find it easy to have sex relatively casually and not fall in love, or even because you, personally, are a woman and still find it easy to have casual sex, doesn’t mean that the “cuddle hormone” story is, in the general case, wrong. People have different levels of all kinds of hormones and neurotransmitters, and different biological receptivity to said chemicals. One of the most publicized of the “cuddle hormone” studies concerns differences between prairie voles, in which sexual behavior are said to be tied to differences in brain receptors for oxytocin and vasopressin. It’s always possible that, to one degree or another, people who have casual sex easily aren’t in denial, but really are physically wired to respond differently (at least in degree) to the same chemicals that make others bond. On the other hand, just because you (as is the case for both me and destinyinprogress) don’t do that well with more casual sexual relationships, doesn’t mean that oxytocin is the reason. It may be, or there may be some entirely different reason.

From my limited understanding of what the scientific evidence actually is, my greatest skepticism isn’t with the “people release oxytocin at orgasm and that leads to bonding” part; though I’m not sure whether even that is actually proven, it sounds as if there are at least some studies pointing in that direction. (And, regardless of exactly how oxytocin in particular turns out to be tied to sexual response, I do believe that, in ordinary experience, bonding during sex is something a lot of people can’t readily turn off – whether or not other people can.) My skepticism is more with the way a lot of popular articles present this purely as something that happens to women. It doesn’t look to me as if what scientific evidence there is supports that conclusion at this point; I think it’s a case of people jumping to conclusions based on their own presuppositions about differences between the sexes (a lot of which can be explained, even without any differences in men’s and women’s oxytocin serum levels at orgasm, by the fact that we all have brains and can perceive that sex has different costs for men and women).

In the interest of finding something more peer reviewed than Wikipedia, I did some Googling to find out what research was being done on oxytocin, at top universities. I haven’t yet turned up a lot about oxytocin and sex, which may say more for my failure to select the right search terms than anything else, but I did turn up some interesting research, at Stanford, on oxytocin and autism.

The researchers will test whether impaired social behaviors in autism are linked to levels of the hormone oxytocin. In healthy individuals, oxytocin primes maternal behavior, enhances social interactions, increases the ability to read facial expressions and recognize individuals, and boosts trust and empathy. Preliminary research has hinted that autism may be associated with oxytocin deficits, but those studies involved limited samples.

So, there does seem to be ongoing research on just what effect oxytocin has on social relationships, but a lot of it seems to be preliminary at this point.

This entry was posted on Monday, January 18th, 2010 at 6:02 pm and is filed under Sexuality. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.