Dr Petra Boyton casts a critical eye on recent media stories suggesting that sex on first date releases ‘brain hormones’ that increase trust and intimacy that might improve the long-term chances of a relationship. So what does neuroscience tell us about the link?
The claim is made by Dr Barry Gibb [insert Bee Gees joke here] in a new book The Rough Guide to the Brain.
The claim is likely based on the fact that the hormone oxytocin has been reported to increase trust in humans when deliberately administered by experimenters, and has been linked to sexual response in humans.
The trouble is, the evidence for a strong and consistent link with sexual response isn’t really there yet.
A recent review article examined the role of hormones in sexual arousal and looked specifically at oxytocin, noting that:
Carmichael et al. (1987) found that plasma OT [oxytocin] increased around the time of orgasm in men and women, remaining raised for at least 5 min after orgasm…. In a recent study of men, OT increased in some subjects following ejaculation, but the individual variability was such that the group effect was not significant (Kruger et al. 2003a).
Murphy et al. (1987) reported an increase in OT in men during sexual arousal, which persisted beyond ejaculation, but with no obvious increase at ejaculation. In a study of women, Blaicher et al.(1999) found an increase in OT 1 min after orgasm, but levels were close to baseline by 5 min post-orgasm.
It is difficult to draw clear conclusions from this literature on OT and sexual arousal. Whether the increase of OT around orgasm, which has been somewhat inconsistently observed in the human literature, has any specific function, rather than being an epiphenomenon of other changes, remains uncertain…
In other words, the evidence for oxytocin being released consistently during sex is mixed and its significance is unclear.
Even if sex and the oxytocin ‘trust boost’ was reliably linked, you would need to do a study looking at whether couples trust each other more after having sex for the first time to really be sure whether the effect actually had an impact.
Sex causes such a strong behavioural, psychological and neurochemical change that a small release of oxytocin might be completely insignificant among the storm of other effects.
So does sex on first date increase the chances of a long-term relationship?
We don’t know, and what we do know about the neuroscience of sexual response doesn’t really tell us either.
UPDATE: Susan Kuchinskas has added some insightful commentary to this post. Check the comments section.
Link to Dr Petra Boyton’s article.
Link to full text of scientific article ‘The endocrinology of sexual arousal’.
Mind Hacks 
I disagree with your analysis of these studies.
First, the Bancroft review looks at oxytocin’s role in sexual arousal, while the Boynton article is talking about oxytocin’s role in bonding. The conclusion that there is no clear role for oxytocin in arousal has no bearing on Boynton’s claims. (BTW, oxytocin definitely plays a part in penile erection, but that’s likely post-arousal.)
Second, you say, “a small release of oxytocin might be completely insignificant among the storm of other effects.” Well, how small is small? And how large does the oxytocin release need to be to have an effect?
Oxytocin’s role in bonding in voles and titi monkeys (and likely in humans) takes place in very small areas of the brain. We’re talking about changes at the molecular level. I think it’s a mistake to discount the possibility of its effects on bonding because the increase in plasma levels is small.
Moreover, these researchers are measuring oxytocin levels in the blood. Most researchers believe that an increase in plasma levels of oxytocin is a good indicator of its release in the central nervous system, but it’s certainly not a one-to-one correlation.
It’s possible that small increases in blood plasma correlate with a huge rush in the nucleus accumbens, the brain’s reward system, where oxytocin likely combines with dopamine to create social bonds.
My personal opinion, based on my own experiences, is that sex does make me feel bonded, aside from whatever else is or isn’t going on with the other person. I think women especially should be wary of the one-night stand, because our higher estrogen levels make our oxytocin receptors more sensitive.
Hi Susan,
You make some excellent points that may turn out to be true. However it is also true that we really don’t know if oxytocin in humans is reliably released in the brain during sex, and, consequently, whether it plays a significant role in sexual bonding.
The studies just haven’t been done yet, and until they have, I think we should avoid promoting these hypotheses as facts. Unfortunately, many of the recent press stories have lacked the necessary caution.
“I think women especially should be wary of the one-night stand, because our higher estrogen levels make our oxytocin receptors more sensitive”
——————————————————————————-
But female promiscuity can lead to healthier offspring, yes? (see:
http://salon.com/mwt/broadsheet/2006/11/03
/marsupials/index.html
).
I agree on the one-night stands, though. I recommend reponsible non-monogamy (see:http://en.wikipedia.org/wiki/Polyamory) because selfishness, jealousy and possessiveness are so overrated dont ya think? Not to mention cheating and divorce.
I do believe Gibbs’ assertion that sex increases intimacy and trust. I guess the question is when is the proper time to start building that trust. I don’t know if the first date is the best time to start bonding with someone. My gut level instincts tell me it’s likely not.