A steady drip of oxytocin may help sustain relationship harmony
Let's start with the partial truths in the oxytocin-orgasm claim. Oxytocin is almost certainly part of the neurochemistry of human bonding. It is released in men and women during warm touch, hugs and prolonged eye contact. According to researcher Paul Zak, the oxytocin-effects of a single hug last an hour. Oxytocin is also involved in long-term bonding in tamarin monkeys and prairie voles.
We can't be certain if oxytocin causes loving feelings, or if loving feelings release oxytocin, or both, but the evidence points to a strong link between the two.
Oxytocin is essential for erections and sexual responsiveness. But climax itself isn't necessary to release oxytocin. During an encounter, oxytocin in brain and blood generally reach their highest levels at climax, but they drop immediately. It seems the "Big O" triggers the return of oxytocin to baseline levels and releases the hormones that induce penile flaccidity. That's right, within five or so minutes of climax, your oxytocin is back where it was before you got frisky.
It's thought that only brain oxytocin affects loving feelings, and it can't yet be measured in humans. (Oxytocin in the blood doesn't appear to cross into the brain.) Nevertheless, research on humans does show that "oxytocin-type" activities increase blood flow in the brain's oxytocin-releasing areas. Blood oxytocin, on the other hand, can be measured. It appears to cause the orgasmic contractions that help move semen around among other jobs.
Other pair-bonding species rely on more than jollies
Even assuming oxytocin is also what makes you feel totally In Love at the Big Moment, its immediate drop-off is not great news for those trying to stay in love. As it recedes, the desire to cuddle often goes with it. Somehow orgasm inhibits the "bonding chemical" in many lovers.
Perhaps the drop-off is why pair bonders (including humans) rely on more than just climax to keep bonds strong. Pair-bonding species spend most of their "us time" engaged in non-copulatory, oxytocin-releasing (bonding) behaviors: Grooming, huddling together, tail-twining, or, in humans, comforting, soothing touch, kissing, skin-to-skin contact, eye gazing and so forth. Interestingly, pair-bonding monkey mates who engage in the most bonding behaviors have the highest oxytocin levels.
These activities, as well as many that are flirtier (including copulation without climax), have an advantage over climax: They don't trigger an immediate return of oxytocin levels to baseline.
Frequent, comforting feelings are important in maintaining strong pair bonds. We only deepen our bonds when we feel safe. What keeps us feeling safe is bonding behaviors (attachment cues). The oxytocin they release relaxes our natural defensiveness (by soothing the brain's sentry, the amygdala, and stimulating good feelings in our reward circuitry). The more dependable the flow of oxytocin via daily bonding behaviors, the easier it is to sustain a relationship. In contrast, a passionate one-night stand allows lovers' innate defensiveness to snap back into place pretty much as soon as oxytocin drops after climax. The next day, when she doesn't text and he doesn't call, defensiveness naturally increases.
Keep in mind that both oxytocin and dopamine (the "gotta get it!" passion neurochemical) are necessary to maintain emotional bonds. Both unfortunately drop after orgasm. So even if you're doing your best to elevate oxytocin with a cuddle after the Big O, you may not be feelin' it. Your desire (dopamine) is also dropping—not to mention often your eyelids. Pumping up dopamine with even hotter action often feels like a solution, but climax causes another drop in both oxytocin and dopamine. (More on an oxytocin-sustaining approach to intercourse in a moment.)
End of the honeymoon
The neurochemistry of passionate love is transient in another sense as well. New lovers are jacked up on special honeymoon neurochemicals, which go far beyond the effects of oxytocin. For example, they have extra nerve growth factor and cortisol flowing through their veins. Dopamine-releasing areas of the brain are activated. Their serotonin is often as low as the levels of OCD patients—which is why lovers obsess over each other. In addition, odd things are going on with their testosterone levels: They're lower than normal in men during early romance, and higher than normal in women—bringing their libidos more into sync. Yet all these potent neurochemicals return to normal levels by year two at the latest. Once that booster shot wears off, cracks often appear.
Intriguingly, there's growing evidence of a subtle neurochemical/hormonal cycle after climax, which can impact mood and shift partner perception, and affects each of us slightly differently. As our honeymoon neurochemistry fades, too much orgasm can leave some lovers averse to hot sex for days—and others more insatiable than ever. Tellingly, even though everyone really likes orgasm, and sex aids abound, only thirteen percent of couples manage to stay romantically in love over the long haul. Fleeting orgasm-related surges of oxytocin do not appear to be the magic bullet for harmony. Yet let's look at them a little more closely before considering another possible lovemaking strategy.
Lust in the Lab
The part of the brain that governs mating is very similar in all mammals, and runs on the same neurochemicals. Even though they aren't pair bonders, rats are excellent models for understanding the neuroendocrine regulation of climax and subsequent events.
In the graph below, you can see that oxytocin gradually increases during rat courtship, peaks at mating, and then gradually drops back down. Very straightforward. Notice that there's no need to climax to raise oxytocin; it's already rising as mates meet. In fact, recent research on female rats shows that oxytocin rises and continues to increase as they draw out their courtships (as opposed to just having their bones jumped right away). Also notice that climax triggers the return to baseline.
The research results for humans are far messier, but raise interesting questions. So far, human trials have only measured oxytocin levels in the blood during masturbation—not intercourse. Here's an expert's short summary of results:
OT [oxytocin] increased in some subjects following ejaculation, but the individual variability was such that the group effect was not significant. 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.... The reader is entitled to feel confused. (emphasis added)
Why the inconsistent human results? Perhaps because the rats were courting and mounting actual mates, not masturbating to erotica-du-jour. Researchers once assumed that biomarkers are no different during solo sex than they are during intercourse—but this is untrue. Brody and Krüger found that orgasm during intercourse releases four times more prolactin than masturbation. Since oxytocin appears to trigger the release of prolactin, it's quite possible that oxytocin released by intimacy accounts for the higher prolactin levels during intercourse.
Given that oxytocin is "the cuddle hormone," tests with masturbation, not copulation, alter a key variable. No one viewing erotica in the lab is cuddling, or even obliged to think about it. Were the test subjects masturbating to softcore or hardcore? Were they imagining contact with a real partner, or strictly in spectator-mode?
While some physiological events after climax may be largely mechanical—drops in dopamine and oxytocin and the rise of prolactin—the levels of oxytocin at other points in a romantic interlude may be strongly related to closeness. For example, maybe those who stay cuddly longer after climax are releasing more brain oxytocin.
Since the benefits of intercourse don't automatically translate to solo sex, singles may want to emphasize other activities associated with mood regulation: interacting or cuddling with friends and potential mates, exercise, yoga, meditation, time in nature, volunteering, exchanging massage and so forth.
Unlike the fiery, fading honeymoon neurochemicals discussed above, the flow of oxytocin can be sustained by employing the same strategy that other pair-bonding species use: frequent bonding behaviors.
Adventurous lovers can also keep the flow more consistent by mastering an approach to intercourse that has gone by various names: karezza, Daoist dual cultivation, cortezia, tantra, amplexus reservatus, and so forth. Lovers emphasize daily affection and pleasurable, non-goal-oriented intercourse to increase and sustain oxytocin while averting the drop-off after orgasm. (Ideal for recovering porn users.)
Even psychiatrist Wilhelm Reich ("Mr. Orgasm" himself) recorded the benefits of "voluntary control of the excitation":
Through the mutual, gradual, spontaneous effortless friction, the excitation becomes concentrated [in penis and vagina]. The characteristic sensation which heralds and accompanies the discharge of the semen is still wholly absent. ... Consciousness is fully attuned to the assimilation of the streaming sensations of pleasure. ... According to most potent men and women, the slower and more gentle the frictions are and the more closely synchronized, the more intense are the sensations of pleasure. ... In this phase, interruption of the friction is in itself pleasurable because of the special sensations of pleasure which attend this pause and do not require psychic exertion. In this way, the act is prolonged.... Interruption of the sexual act by withdrawing the penis not unpleasurable as long as it occurs after a restful pause. (Wilhelm Reich, The Function of the Orgasm, Farrar, Strauss and Giroux (1973): 102-5.)
Reich also noted that this technique increases harmonizing, or attunement, with one's lover. Was he, like other observers throughout thousands of years of human history, indirectly acknowledging the power of oxytocin to strengthen the harmony and satisfaction of lovers?
Even if orgasm won't keep you in love, a steady drip of oxytocin-producing affection and lovemaking just might.
For science buffs: Growing evidence of a lingering post-orgasm cycle (links to studies)