In the first study of its kind, a team of scientists at Carnegie Mellon University have upended the common notion that having more sex will make you happier.

In fact, more sex might even generate unhappiness, George Leowenstein, a professor of economics and psychology at Carnegie Mellon, and his colleagues report in their recent paper.

Several studies over the last decade have found evidence to suggest that sex is directly linked with happiness, so that more sex means greater happiness. One study even found that changing the amount of sex you had from once a month to once a week would give you the same amount of happiness as receiving an extra US$50,000.

However, what these studies missed and what’s causing some misconceptions about sexual frequency and joy, Leowenstein recently told The New York Times, was to determine which element - sex or happiness - was the cause and which was the effect. Not only that, other factors besides sex, such as income, location, or age, could be better gauges of what makes us happy.

"Although it seems plausible that sex could have beneficial effects on happiness, it is equally plausible that happiness affects sex," the team wrote in their paper. "…or that some third variable, such as health, affects both."

To help settle this riddle, the team carefully designed an experiment that would clearly determine, once and for all, if more sex causes greater happiness.

A straightforward experiment to solve a confusing riddle

The experiment was straightforward: Measure how happy couples were with their current sex schedules. Then, split them into two groups and ask one group to have more sex (twice as much, to be exact) and ask the other group to change nothing about their sex live. Finally, compare their how happy they were afterward. (As part of the experiment, for example, couples having sex three times a week had sex six times a week; those having sex once a month had it twice a month).

A total of 64 adult couples volunteered. Each pair was legally married and heterosexual, and all volunteers were between the ages of 35 and 65.

The team asked half of the couples to double the amount of sex they were having while the other half of couples kept their normal sex schedule.

Throughout the duration of the experiment, which lasted 90 days, both sets of couples completed the same online questionnaire at the end of each day. This questionnaire helped the researchers measure each couple’s mood as well as how satisfied they were with each sexual episode - the quality of the sex.

What they found surprised them. "Contrary to what one would expect if the causal story running from sexual frequency to happiness were true," the team wrote in their paper, "we observed a weak negative impact of inducing people to have more sex on mood."

In general, the researchers found that the couples who doubled the amount of sex didn’t enjoy the sex as much and were less happy overall. Although the team can only speculate as to why this was, they did answer their question: More sex does not make us happier.

Moreover, the researchers stipulate that by being forced to have more sex, the selected couples actually developed, over time, less motivation to have sex. That, in turn, is what might have led to an overall downturn in the quality of their sex as well as their overall mood.

What you want to take away from this, Leowenstein told The Times, is that when it comes to sex, concentrate on quality and not quantity if you want to be happy.

This article was originally published by Business Insider.

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