My oldest daughter is in second grade—she’s still at an age where Valentine’s Day means giving cards to everyone in her class, and receiving cards from everyone as well. There’s a lot of security and a lot of joy that comes with second-grade Valentine’s Day: Everyone is affirmed, and many cards come with lollipops attached. It gets much more complicated as we get older. Nonetheless, research on young adults and marriage also finds key roles for affirmation and security. This is not unambiguously good news for couples celebrating Valentine’s Day in the United States this year, because dating and cohabitation often offer much affirmation and other positive social benefits, but don’t provide much in the way of security.

Why should that matter so much on Valentine’s Day? Can’t a day celebrating romantic love simply be a celebration of love on that day, without attention to what tomorrow holds? Apparently not. Research on the benefits deriving from relationships seems to indicate that people are happier in more committed attachments.

On the one hand, we intuitively know this: It isn’t a good Valentine’s Day if your partner agrees to make the dinner reservation, but asks if it is OK to wait until a week ahead of time instead of making it earlier, in case you break up in the meantime. On the other hand, our intuitions balk at the idea: My friend’s 19-year-old son had a very hard time waiting for the snowplows after the recent blizzard in DC, because he couldn’t wait to see his girlfriend of several months. Somehow I imagine their Valentine’s Day will be more passionate than my parents’ will, even though my parents have all the benefits of 57 years of marriage.

As unromantic as it might seem, turning to social science research is a good way to sort things out when intuitions conflict. And good research compares apples to apples, not 19-year-olds to seventy-somethings. One piece of Baylor sociologist Jeremy Uecker’s work focuses on young adults in six different relationship arrangements: single, dating and unengaged, dating and engaged, cohabiting and unengaged, cohabiting and engaged, and ever married. He confirmed that young adults in any kind of romantic relationship had less psychological distress than singles.

Importantly, Uecker also showed that the disadvantage to being single was mostly explained by relationship instability: Singles were more likely to have had two or more sexual partners in the past year, and partner turnover was related to psychological distress. I think that means that my friend’s 19-year-old son might be giddy in part because he’s dating his first girlfriend, but that he won’t be as happy next Valentine’s Day if he’s on his fourth (no matter how lovely she may be). It is also consistent with other work showing that higher rates of depression among cohabitors than married people are mostly explained by relationship instability.

Uecker’s research offers further evidence supporting the theory that commitment contributes to happiness: Engaged and married people drink less alcohol than singles and unengaged daters, and married people are more satisfied with their lives than everyone besides engaged cohabitors (marrieds and engaged cohabitors were equally satisfied).

Many readers may be nodding at the idea that relationships contribute to mental health and that committed ones contribute even more, but balk at the proposal that marrying is a good idea for young people. After all, couples marrying in their teens and early twenties are more likely to divorce than those marrying later. But consider that marriages occurring around age 25 are happier and no less stable than those occurring in the late twenties. What does that mean in a country where the average age at marriage is creeping toward 30? I think it means that many are delaying gratification a little too long.

There are many reasons why Americans generally don’t embrace the idea that it is good for the young to marry, but let me address an important reason why social scientists are slow to embrace that conclusion: When people who marry differ from people who don’t in a myriad of ways, it is difficult to establish that marriage actually changes anything. In other words, when married people are happier, healthier, and abuse substances less than their unmarried counterparts, it is difficult to show that they would not have been advantaged even if they had never married.

On this question of causation, Uecker argues persuasively that young married couples would not, in fact, show similar advantages were they not married. Those who married in their teens exhibited far more psychological distress before marriage, and those marrying before the late twenties had fewer economic resources at the time of their wedding than those remaining single. This contradicts the story at older ages, where the argument goes that married people are better off because those with mental health problems and those lacking financial resources are less likely to marry, and thus the apparent advantage of the married may not have come from marriage. Were they not married, younger married people would be worse off than their peers who are currently unmarried, yet Uecker shows that on some outcomes, they now fare better.

The question of causation has also been tackled with help from genetics. In a 2013 study, Erin Horn and her colleagues made use of identical twins, fraternal twins, siblings, half-siblings, cousins, and step-siblings to control for both genetic influences on physical and mental health as well as (un)shared environments during childhood. They came to essentially the same conclusion Uecker did: Young adults enjoy better mental health if they are in relationships, especially if they are married.

I am all in favor of celebrating marital love this Valentine’s Day. The research is more complicated than second-grade classroom parties, but the conclusions are fairly straightforward—even for young adults.