In a nation as divided and contentious as our own, it is rare to find a belief we all share. But trust in the transformative power of marriage is close to universal — and it has endured for decades. This isn’t just a matter of faith, we’ve been assured. It’s science. Research is said to have established what our fairy tales promised: Marry and you will live happily ever after. And you will be healthier, too.

A new study challenges the claim that people who marry get healthier. In “The Ambiguous Link Between Marriage and Health,” recently published online in the journal Social Forces, the sociologist Matthijs Kalmijn reported findings from the Swiss Household Panel, a 16-year survey of a nationally representative sample of more than 11,000 Swiss adults. Every year, participants were asked one set of questions about their overall health and another about their illnesses.

If marriage makes people healthier, then people who marry should report better overall health and less illness than when they were single. If the purported benefits of marriage are cumulative, then people should get even healthier over the course of their marriages.

That’s not what happened. People who married reported slightly worse health than they had when they were single. Over time, their health did not improve — it tended to deteriorate, even after taking into account changes in health as people age. On the measures of illness, marriage made no difference at all. People who married did not become any more or less ill than they were when they were single, and their level of illness did not change over the course of their marriage.