02/07/2011 09:04 am ET Updated Nov 17, 2011

Marriage: Does It Really Make a Difference in a Relationship?

Many, many episodes ago on my podcast Stuff Mom Never Told You, I jokingly commented to my co-host Molly that life would be a lot easier if society abolished marriage. We had been discussing the differences between civil unions and marriages, and after dissecting the legalese at length, I mentioned that maybe we should just do away with the whole thing. Let folks couple up as they will and call it a day.

It wasn't a serious proposal on my part. Like a good relationship scholar, I've read Stephanie Coontz's "Marriage: A History" and understand the whys and wherefores of this most-exalted institution. Married people tend to report being happier than singles, and a pair of economists once calculated the monetary value of that wedded bliss at $100,000 per year. Getting hitched might also proffer physical benefits, as statistics show that spouses drink and smoke less, have fewer headaches and often live longer than unmarried folks. At the same time, we're living in a divorce-heavy, cohabitation-happy society. So what gives?

While researching for a recent podcast on whether the seven-year itch exists, Molly and I ran across a number of 2007 articles reporting on a study finding that marital satisfaction actually drops off around the three-year mark. (Talk about a fast decline!) However, when I tracked down the actual study -- "Re-Examining the Case for Marriage: Variation and Change in Well-Being and Relationships" by Kelly Musick and Larry Bumpass -- the research wasn't looking for when the honeymoon phase ends. Musick and Bumpass set out on their meta-analysis because "literature on the benefits of marriage and cohabitation has largely ignored how well-being changes as marriages and cohabitations progress over time, despite clear evidence of relationship instability." And in fact, that "three-year itch" was a mere side note in its rich findings.

The study instead re-examined a vast body of research on marriage and cohabitation in order suss out "how marriage compares to other intimate relationships or whether the benefits of marriage persist over time." Do unmarried, cohabitating couples derive just as many mental, physical and social benefits from their relationships? To sum up the 60-page study: Yes.

When you break down individual benefits of coupling up, it doesn't make that much of a difference whether you do it through cohabitation or marriage, as the study explains:

The only statistically significant difference between marriage and cohabitation is in happiness, and here, those that enter directly into marriage report smaller gains in happiness than those who cohabit... Only cohabitation has a statistically significant effect on self-esteem relative to remaining single, at increasing levels. Cohabitation also increases self-esteem compared to marriage (again, both direct marriage and marriage preceded by cohabitation). In sum, while marriage appears to confer advantages in health relative to cohabitation, the opposite is true of self-esteem, and entering into any union appears to improve happiness and depressive symptoms.

When examining how those long-term "unions" affect happiness, Musick and Bumpass unearthed another interesting tidbit that confounds a lot of what we hear about how finding your one-and-only is the key to personal fulfillment:

Compared to singles, a higher proportion of men and women entering into unions report gains in happiness: 41 percent of those marrying directly, 49 percent marrying following cohabitation, and 47 percent cohabiting only, compared to 37 percent remaining single.

So while a lot of people experience a happiness boost from entering into long-term relationships, it isn't a panacea. In other words, marriage (and cohabitation) doesn't necessarily guarantee all of those benefits attributed to it. According to Musick and Bumpass' data, the only difference marriage makes is that it might predict physical health. The revered institution doesn't degrade your quality of life, but it might not transform it into a sparkling wonderland any better than other forms of intimate couplings.

Granted, this is just one study, and statistics can't confer the individual value of lasting unions. And clearly, humans derive plenty of joy that translates to improved mental and physical health from positive, intimate relationships. But if couples expect marriage to make an enormous difference in their well-being, they might be disappointed in the long run -- or at least after three years or so.