Is sex the key to a lasting relationship? It appears to be the case, according to some new research, but the full picture is complicated, and the findings raise an obvious question: What enables and sustains a couple’s long-term romantic and sexual connection, to begin with?

Let’s take a look.

This study focused on recently married couples and found links between the frequency of sex and its positive impact on the relationship over time. (Previous research has also found a similar effect among older couples.) Needless to say, if both partners enjoy sex, per se, and presumably with each other, then yes, that’s likely to enhance their relationship satisfaction. But what enables that desire, in itself? We know that long-term relationships often head south over time: Diminished energy and intimacy in your relationship inevitably affects you and your partner’s sexual connection. That is, the state of your relationship will follow you into the bedroom.

So, just having sex, in the absence of a thriving relationship, is unlikely to be very pleasurable, nor will it translate into increased marital satisfaction over time; actually, it could diminish it. Mental health professionals who’ve worked with relationship issues recognize that from our patients’ experiences in therapy. True, some couples try to smooth over a flatlined or troubled relationship by trying to just have sex anyway, or by having “make-up sex” or even “angry sex” after a fight. Other couples look to recharge their sexual relationship by turning to the latest techniques or suggestions from books, workshops, or the media.

These are understandable but misguided efforts, and they reflect a broader problem: We absorb very skewed notions about sexual needs, behaviour, and romantic relationships as we grow up. (I described some of the dysfunctions that result in an earlier post about the differences between “hook-up sex,” “marital sex,” and “making love.”)

But in contrast, couples’ actual experiences and some empirical research show what partners do when they are successful at sustaining the positive connection, emotionally and sexually. In essence, they build and live an integrated relationship, one that combines transparency in communication, conscious mutuality in decision-making, and a commitment to creating conditions for maintaining erotic energy in their physical/sexual life.

The key role these habits play becomes more evident when looking at the actual findings from the study of recently married couples. Conducted by Florida State University and published in Psychological Science, it looked at whether frequent sex might not only sustain partners’ positive connection between periods of sexual activity, but might also strengthen their long-term relationship satisfaction.

The researchers found that a single act of sex produced an “afterglow” for couples that lasted for about two days. More significantly, couples experiencing a stronger afterglow reported greater marital satisfaction four-to-six months later compared with those who reported a weaker afterglow.

According to lead author Andrea Meltzer, “Our research shows that sexual satisfaction remains elevated 48 hours after sex, and people with a stronger sexual afterglow — that is, people who report a higher level of sexual satisfaction 48 hours after sex — report higher levels of relationship satisfaction several months later.” The research was based on data from two independent, longitudinal studies of 214 couples, and is described in detail in the journal’s news release.

But the study also found that some couples didn’t experience much “afterglow” at all after sex. More significantly, all couples’ marital satisfaction declined between the beginning of the study and its follow-up, four-to-six months later — although those who reported higher initial satisfaction experienced less decline.

So decline occurred over time, regardless of the degree of “afterglow.” Actually, that’s pretty consistent with what most long-term couples experience — and lament. When your relationship declines, it affects your sex life. The researchers’ conclusion that “sex functions to keep couples pair-bonded” overlooks this reality: No sexual technique or efforts to re-energize passion will help much when your relationship’s vitality is ebbing away.

What Helps?

A sustaining energized sexual relationship is a product of an integration of multiple facets. It grows over time from being in sync with each other’s values and outlook; your desires and fears about your journey together; your life goals, both individually and as a couple. Essentially, it’s a spiritual connection, a sense of being on the same wavelength. If that core grows, it will fuel a sustainable romantic connection — which, in fact, research shows most couples desire.

I think it’s useful to see three dimensions of an integrated relationship, each reinforcing and strengthening the others — Radical Transparency, Sharing the Stage and Building Good Vibrations. (This article provides more description of each of these.)

In brief, Radical Transparency means communicating truthfully and completely to your partner. It’s a two-way process: Being fully open to hearing your partner's feelings, wishes, desires, and differences from yourself, and revealing your own to your partner, without inhibition or defensiveness. It includes each other’s vulnerabilities and fears, as well as desires and points of view about everything. It’s hard; something to practice.

Sharing the Stage refers to partners showing equality and mutuality in issues of daily life, neither dominating nor submitting to each other in decisions or areas of conflict. For example, in decision-making, especially where there are differences, each of you would think of what best serves the relationship — visualizing it as a third entity — rather than your own ego.

“Good Vibrations” build in your sexual-physical relationship from radical transparency and sharing the stage, as you become more comfortable with open communication and extend that to your sexual desires and needs. It also requires that you take the time and the setting for focusing on each other, physically and sexually. You have to create “adult” time — without the kids. It’s clear that couples who build long-term, thriving relationships will likely sustain a sexual/physical relationship as an integrated part of it — especially if health or other issues make sexual intercourse less possible.

For example, one study of couples in their mid-60s through mid-80s found that couples who had more frequent sexual encounters — including any sexual act, not just intercourse — had happier, more positive marriages than those who were less sexually active. That study pointed out the connection between the couple’s sexual life and their overall relationship, as I’ve described. And, interestingly, research using brain imaging has found that older couples who’ve sustained positive, integrated relationships show brain patterns indicating “very clear similarities between those who were in love long-term and those who had just fallen madly in love.”