People who have a lot of sex tend to be happy.

Obvious? Perhaps. But here’s what we don’t know: Does more sex make people happier? Or do happy people just do it more?

A gaggle of economists and statisticians lead by Carnegie Mellon University’s George Loewenstein, a well-known behavioral economist, have done their best to find out.

Their study, published in the Journal of Economic Behavior & Organization, finds that more sex doesn’t always make people happier—especially if the increase is the result of taking part in an economics experiment.

Using local newspapers, advertisements and flyers, the researchers recruited 64 married couples between the ages of 35 and 65, who met certain baseline health and sexual activity criteria. They were randomly separated into a control group and a group that would be asked to change behavior, known as the treatment group. Over the next three months, couples in the treatment group were asked to double the amount of sex they had, while completing daily surveys about their mood (happy? sad? cheerful? tense?) and updates about sexual activity and their attitude toward it.

The upshot? Participants who were asked to have more sex reported lower mood than the control group. The researchers dug into the survey responses among those who were urged to double their sexual activity. They found that participants’ responses suggested significant shifts in energy and excitement, or lack thereof. (Simply put, participants were tired.)

So is more sex now a bad thing? Probably not. The findings seem to indicate that “the instruction to have more sex leads to a decline in wanting for sex and in enjoyment of sex.”

“One possibility might have been that people are unhappy because we are driving them to have more sex than their ideal, than the amount they would have had naturally on their own,” says Loewenstein, but he cautions that it’s important to keep the finding in perspective. “I don’t think it generalizes to the point that it’s bad for couples to have more sex,” he adds.

At any rate, at least we know conclusively whether participation in behavioral economics studies is the best way for married couples to spice things up. The answer is no.

Correction: A previous version of this post misspelled Loewenstein’s name on first reference.