Thinking about tying the knot? You’re probably wondering if — and how — such a big commitment will impact your relationship.A friend who knows I’m in a long-term relationship recently sent me a New York Times’ opinion piece titled “13 Questions To Ask Before Getting Married.” What she probably doesn’t know is that she sent me on an entirely different research mission: to see what we know about the effect marriage actually has on peoples’ happiness.

Sure, you may have heard that married people report being happier overall over their lifetimes than single folks, or that people tend to say they’re more “satisfied” with life just after their weddings.

But is it actually the act of marriage that’s causing those benefits?

Probably not.

In fact, there’s loads of evidence to the contrary: A 2012 study found that couples who lived together but were not married had higher self-esteem and were happier overall than their counterparts who were married. A 2011 review of the impact of happiness on major life events found that couples who got married generally felt less happy and less satisfied over time than couples who had not.

More importantly to me than all these negative studies, however, was a recent bright spot in the research which suggests that it isn’t marriage that’s the key to happiness, but the quality of the relationship itself.

A 2014 working paper from the National Bureau of Economics Research found that if the person you call your partner (or significant other, or whatever) is also the person you see as your best friend, you don’t actually need to be married to reap the benefits of a long-term relationship. And it’s this factor, rather than getting married (or not) that appears to matter the most for happiness.

For their 2014 paper, the researchers’ initial findings appeared to support the “if marriage, then happiness” idea: They found that couples who were married tended to have higher happiness levels than couples who were not.

But the second part of that finding threw it out the window: It turned out that the couples who were best friends and lived together were just as happy as couples who were best friends and married. In other words, marriage didn’t appear to matter much at all.

To arrive at their conclusions, the researchers studied three separate data sets that included information about thousands of couples: The United Kingdom’s Annual Population Survey, the British Household Panel Survey, and the Gallup World Poll. Then, they controlled for couples’ age, gender, income, and health conditions (all of which could potentially affect their results).

People in a relationship who saw their significant other as their best friend and either lived with that person or married them were happier than couples who saw their best friend as someone outside of the relationship.

“What immediately intrigued me about the results was to rethink marriage as a whole,” University of British Columbia economics professor and study coauthor John Helliwell recently told the New York Times. “Maybe what is really important is friendship, and to never forget that in the push and pull of daily life.”

But that’s not all.

“What is really remarkable about the combined findings of the 18 studies,” writes DePaulo, “is that the designs were biased in favor of making marriage look good. At least 11 of the studies included only those people who got married and stayed married.”

For another 2012 study (this one a survey of American couples), researchers found that couples who lived together but were not married had higher self-esteem and were happier overall than their married counterparts. Both types of relationships, however, were still linked with increases in overall well-being.

Other studies suggest that marriage might even be more closely linked with negative outcomes than positive ones: A 2011 review of the impact on happiness of major life events found that couples who got married generally felt less happy and less satisfied with their lives over time.The key takeaway here? Find a partner you consider your best friend. And don’t worry so much about the other stuff.