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In social science, it’s not enough to know that things happen, but why they happen. Like, for instance, the finding that having sex once a week makes people way happier than once a month. It’s equivalent to making an additional $50,000 per year, Christian Jarrett points out at the BPS Research Digest. The question, though, is why sex produces such effects not just for in-the-moment pleasure, but a greater sense of well-being. That’s where a new study in Personality and Social Psychology Bulletin comes in — apparently, it’s all about the cuddles. “[S]ex seems not only beneficial because of its physiological or hedonic effects, “ writes University of Toronto postdoc Anik Debrot and her colleagues, “but because it promotes a stronger and more positive connection with the partner.”

The study was composed of a several experiments. In the first, 335 Americans in romantic relationships were recruited online. They were quizzed on their sexual frequency, their life satisfaction, and their “affectionate touch frequency” — or how often they cuddled, kissed, and the like. Another was of 74 couples recruited from the San Francisco area. Frequency in sex and touch were both linked to feeling good about life, but after some number crunching, the researchers declared that it was the affection that mediated the gains in well-being.

Following up on that, a diary-based experiment with 106 Swiss couples (mostly parents) found that the more sex a couple had over a ten-day period, the higher their relationship satisfaction six months later — so long as, Jarrett notes, their earlier sexual experiences had lots of positive emotions. Another follow-up found that when couples had sex, they were more likely to report experiences of affection not just in the immediate aftermath, but several hours later. Like a separate sex researcher told Science of Us not too long ago, mutual sexual absorption has a way of bonding people.

With studies like this, reliant on surveys and diaries, it’s hard to isolate just what the root mechanism is. Experimental study designs are better for that task, but it’s hard to find the right approach for studying a topic like this one — do you ask one group of couples to have sex and be affectionate, and the others to be coolly distant with each other? Also, it’s not unreasonable to think that the sex and the cuddling and the well-being are all boosting the effectiveness of one another, in one snuggly feedback loop. Still, even with that caveat, this study isn’t just useful for its practical message — be affectionate, it’ll deepen the benefits of sex and help your relationship — but for the way it bridges two subfields that are so unfortunately disconnected: close relationships and sexuality.