Are lovers struggling against a neurochemical tide?
It seems like a "no-brainer" that more orgasms and more intense orgasms will satisfy more. However, the "I'm done!" feeling after orgasm delivers a powerful subconscious signal to the limbic brain, which can create restlessness down the road. Is it time to rethink our lovemaking strategy?
Both sensual Romans and sex-positive ancient Chinese Daoists recognized that sexual satiety shifts perception. Over two thousand years ago, Ovid, the elegantly earthy poet, wrote that the "cure for love" is to satiate oneself with orgasm. Want to stay in love? The earlier Chinese Classic of Su Nu states, "If one engages in sex without emission...exercising self-control and calming the passion, love actually increases." Could couples improve the harmony in their relationships, by learning to use sex as a bonding behavior while tiptoeing around sexual satiety when possible?
In Orgasm's Hidden Cycle, I suggested that orgasm kicks off a surprisingly long neurochemical cycle. Cycles are not unique to the experience of orgasm. The body constantly restores homeostasis through rising and falling levels of hormones and neurotransmitters. Some are programmed (sleep-wake, menstrual cycles), while some occur in response to changing conditions (blood sugar levels, water levels).
Scientists are beginning to turn up evidence (via MRIs, plasma hormone levels, and glimpses into the brains of rodents) of a "passion cycle" after orgasm. However, researchers don't always reflect on the psychological implications of their findings. What happens when subconscious shifts in our neurochemistry alter the emotional tone of our limbic brain well after orgasm? Might such shifts create feelings, which we unknowingly project outward, onto our mates?
A lot happens after orgasm—although there is still much to learn. It's easiest to envision what is known if you keep in mind that most of the neurochemical events appear to revolve around dopamine and the brain's reward circuitry.
As we become sexually aroused, dopamine (the "I gotta have it!" neurochemical) rises in our reward circuitry. It is also implicated in addictions. In fact, in 2003 Dutch scientist Gert Holstege announced in a press release pertaining to his research that brain scans of orgasm resembled brain scans of shooting heroin. What goes up must come down.
You might think that your dopamine levels would obediently return to baseline levels immediately after orgasm, and that you'd be good to go from where you began, neurochemically speaking. Alas, this is not how the reward circuitry of your limbic brain works. When a thunderstorm roles in, you close all the windows. Your brain does something similar following intense stimulation, except that it assumes another storm is coming, and keeps them closed for a while.
After too much hyperstimulating food, for example, rats' dopamine receptors were still somewhat depleted two weeks after they returned to normal chow. As a recent American Society of Addiction Medicine statement explained,
When one engages non-pathologically in potentially addictive behaviors such as gambling or eating [or sex], one may experience a "high", felt as a "positive" emotional state associated with increased dopamine and opioid peptide activity in reward circuits. After such an experience, there is a neurochemical rebound, in which the reward function does not simply revert to baseline, but often drops below the original levels. This is usually not consciously perceptible by the individual and is not necessarily associated with functional impairments.
At climax, dopamine drops (and/or nerve cell receptors for dopamine decline, leaving your reward circuitry less sensitive to dopamine). At the same time, the neurohormone prolactin shoots up. Like most hormones, prolactin has many jobs in the body. After orgasm it acts as a "sexual satiation" substance, suppressing dopamine. Dopamine is an accelerator; prolactin is like brakes.
As prolactin researchers Kruger et al point out,
A series of studies showed that orgasm in humans induces pronounced and long-lasting secretion of peripheral PRL [prolactin] with significantly higher levels of PRL in females... The magnitude of the PRL increase following intercourse was 400% greater than following masturbation, which may indicate the biological significance of cervicovaginal stimulation and/or physical contact with a partner....The inhibitory effects of PRL on sexual appetence in humans are well known....and [deserve] further investigation.
...Preliminary data by our own research group might indicate an altered PRL secretion pattern [in humans] after sexual intercourse ... We assume that the pronounced PRL surge triggered by sexual contact causes a disturbance in the PRL-DA [dopamine]-oxytocin balance of the hypothalamic and pituitary system that, in turn, leads to a significant change in the PRL secretory pattern.
Interestingly, other recent research has found that about 8 percent of women experience post-coital irritability and motiveless crying. Are such symptoms related to prolactin?
Research on other mammals also shows that after orgasm other changes occur. First, enkephalins (endogenous opioids) are elevated for more than 24 hours in some brain areas, and more than two days in the hypothalamus. And this happens after one ejaculation, or after many. Opioids have been shown to inhibit oxytocin neuron activity, which may decrease feelings of satisfaction. Sexual impotence is associated with increased production of opioids and reduced production of oxytocin. Are opioids leaving some lovers restless and dissatisfied over the days after orgasm?
Second, androgen receptor density in the reward circuitry decreases, and the reduction is greater with each copulation. Lowered androgen receptor density means that key brain centers temporarily aren't responding as strongly to important sex hormones, such as testosterone (which influences dopamine, and thus mood and libido, in both men and women).
Oxytocin also surges briefly after climax (although prolactin is considered a more reliable marker of the Big O.) As oxytocin is known as the "bonding hormone," many people assume orgasm must be first-rate glue for lovers. However, like prolactin, oxytocin performs many different jobs in the body, and the orgasm surge may be related to the contractions of orgasm itself (oxytocin is also behind labor and lactation contractions). This surge also appears to trigger the rise of prolactin (the "sexual satiation" neurochemical) and penile flaccidity. Certainly, if orgasm tightly bonded lovers, we'd see very few one-night stands...and a lot more johns in love with their hookers. See Will Orgasms Keep You in Love?
Lovers who wish to strengthen their emotional bonds are likely to make more progress with daily skin-to-skin contact, gentle stroking, and gentle intercourse. This kind of affectionate, generous contact also produces oxytocin and soothes the regions of the brain that need to relax in order for us to bond. The occasional blast of oxytocin at orgasm, which drops soon afterward (along with dopamine), probably isn't as reliable a bonding mechanism. When dopamine drops your mate registers as less rewarding, even if you dowse your limbic brain with oxytocin. We need the right levels of both dopamine and oxytocin for that loving feeling.
In most mammals, these predictable post-orgasmic neurochemical events quiet sexual desire until the brain and libido recover naturally. A novel mate, however, can produce a jump start (dopamine surge). This explains how this "hangover" serves our genes.
We humans, of course, often don't wait. We find it easy to boost sagging dopamine after orgasm. Some options help restore balance without throwing us back onto the dopamine roller coaster: friendly interaction, time in nature, meditation, exercise, and so forth. But many of us reach for stronger "medication" (higher dopamine surges). We gamble, spend money, grab junk food, drugs or alcohol, or fantasize about, click to, or engage in, more sexual stimulation.
Bouncing from lows to new highs, we need never experience equilibrium again! However, as biologist Robert Sapolsky observed, there is a price for blasting our reward circuitry too enthusiastically in our efforts to counter the blues. "Unnaturally strong explosions of synthetic experience and sensation and pleasure evoke unnaturally strong degrees of habituation.... Our tragedy is that we just become hungrier." In short, there are advantages to steering for equilibrium initially, rather than always reaching for more stimulation to cope.
Does declining dopamine in response to a partner have the power to disillusion lovers? A few years back, Doctor Kiecolt-Glaser set out to discover whether stress hormones rose during marital conflict. To isolate short-term stress she chose ninety newlywed couples out of the whopping 2,200 newlywed couples she and her colleagues interviewed. Only the most blissful, healthiest, wealthiest, most stable couples were selected.
Conflict indeed raised stress hormones (with possible implications for lowered immunity to disease). However, in following up with the couples, she also discovered that across the board, they reported decreased satisfaction in their marriages by the second year. As Kiecolt-Glaser put it, "Declines in marital satisfaction appear to be a stable response to the first year or two of marriage." That's scientist-speak for "the poison on Cupid's arrow had taken effect." By release of the study, a fifth of her blissful, ideally suited couples had already divorced.
No doubt the natural decline in honeymoon neurochemistry contributed to these results. However, the fact that couples who employ karezza and daily bonding behaviors show resistance to this natural decline suggests that frequent fertilization-driven sex (often followed by growing alienation and therefore too little affectionate contact) may contribute to emotional dissatisfaction between mates. If so, couples could greatly benefit from knowledge of this passion cycle and information about how humans have learned to get around it.
How long is the passion cycle on average? No one yet knows. We do know that in human males the neurochemical sequence after ejaculation is at least 7 days. (Testosterone predictably spikes briefly around day seven.) However, men and women who observe themselves carefully notice changes in mood that flicker on and off for about two weeks. Perhaps this cycle is an evolutionary remnant of an ancestor's mating season.
Among our fellow mammals, rats have been studied the most. Their limbic systems are so similar to ours that they have been called "guiding flashlights" for understanding the primitive mechanisms of our own brain. Interestingly, it takes up to 15 days for male rats to recover their libido fully after sexual satiety. Female rats also show evidence of a 14-day cycle in the form of predictable surges of prolactin after vigorous copulation, whether or not they become pregnant.
If this cycle exists in humans, it's evident that everyone's experience of it would be somewhat different. Numerous factors appear to affect how we experience it, such as degree of sexual surfeit, whether a partner and loving affection are present, the type of sex (intercourse or not), and, of course, individual sensitivity to pertinent neurochemicals.
Psychologists are uniquely suited to grasp the implications of this phenomenon. More than most neurobiologists, they are aware that subtle changes in feelings (even those brought on by perfectly normal neurochemical fluctuations) can be projected onto others. Projections then mold our experience of the world—and our perception of our mates-without our conscious awareness. No partner, however tolerant or attentive, can consistently soothe our discomfort, or fill a "hole" inside us, which we are experiencing because we have disrupted our neurochemical balance with too much of a good thing.
[Also see Has Evolution Trained Our Brains to Gorge on Food and Sex? for a discussion of the possible significance of D2 receptor decline after intense stimulation.]
And for science buffs: Growing evidence of a lingering post-orgasm cycle (links to studies)