Science can't answer the question for everyone, but there are a few red flags — including your age and your motivations for moving in together — that suggest maintaining separate residences might be the way to go. Perhaps the main message is that sharing an address should be approached as carefully as tying the knot.
There are pros and cons to both marriage and cohabiting, said Stephanie Coontz, a historian at The Evergreen State College in Olympia, Wash.
"It's easier to get out of a bad relationship in a hurry if you're cohabiting, but it's also easier to enter one that you have to get out of," said Coontz, who studies changes in American families and gender roles. [5 Facts About Couples Who Live Together]
Living together without rings
For years, social scientists have warned that cohabiting couples aren't as stable as married couples; of course, the types of couples who marry versus move in together might be very different, meaning that it might be personality or economic circumstance that explains the difference, not the legal institution. Nevertheless, the link betweencohabiting and instability has led some groups, like the academic National Marriage Project, to advise against moving in before marriage.
Despite such warnings, cohabiting remains common. Between 2006 and 2010, about half of married women reported having lived with their partners before the wedding, according to a 2013 report by the Centers for Disease Control and Prevention. And 75 percent of all women under age 30 said they'd cohabited with a partner at some point.
Recent research even suggests that some cohabitation warnings may be overblown: A study by sociologist Arielle Kuperberg of The University of North Carolina at Greensboro found that cohabitation before marriage does not raise the risk of divorce. Rather, cohabiting couples appear more likely to divorce because they move in together at a younger age than couples who wait until marriage to share a home.
That finding leads to the first, and perhaps clearest, piece of advice for young couples in love: Give it time. Moving in (or marrying) when you're young is linked to high rates of divorce.
"When you're young, you don't really know what you want yet," Kuperberg told Live Science. "That's when people are still figuring things out."
An 18-year-old who gets married has approximately a 60 percent chance of divorcing by age 28, Kuperberg said. For those who marry at age 23, that risk drops to 30 percent, after which it stays fairly steady. There's probably no magic to the age 23, Kuperberg said. Rather, it's the age when people tend to finish college and figure out their life plans. Moving in with or marrying a partner before that time carries a larger risk of picking someone who won't fit into those plans. [6 Scientific Tips for a Successful Marriage]
Maturity and money
Taking a good, hard look at your own personal level of maturity also probably wouldn't hurt. Modern marriages require a lot more maturity than marriages in the 1950s, Coontz told Live Science. In the old days, a woman often moved from living with her parents to living with her spouse, and both the man and the woman stepped into prescribed gender roles.
Today, coupledom looks like whatever the members of the couple want it to look like. That's liberating, but it also requires communication.
"You need much more maturity and negotiation skills," Coontz said.
Highlighting the importance of maturity, University of Illinois at Chicago economist Evelyn Lehrer has found that the later a woman enters into marriage, the less likely she is to divorce — even though late marriages disproportionally include unconventional pairings, such as ones in which the couple don’t share a religion, or are far apart in age. Other studies find that these characteristics alone are risk factors for divorce, as they can lead to conflict. But marrying late in life seems to come with mature, realistic expectations about love, Lehrer told Live Science.
Lehrer's research points to another argument for taking your time to move in together or marry: money. Women who marry later have "an opportunity to invest more in their education and their careers," she said, and so do their husbands.
Regardless of age, the length of time a couple waits to move in together may also contribute to their likelihood of breaking up. Cornell University professor Sharon Sassler has been interviewing cohabiting couples and has found that working-class couples are far more likely tomove in together within six months of starting to date than college-educated couples.
Sassler hasn't yet proved that these quick starts lead to more breakups, but less education is linked to a higher risk of divorce. Fast relationship trajectories could be one reason why.
Both the more- and less-educated couples referred to financial benefits when explaining their decision to move in, Sassler told Live Science. But the working-class couples were more likely to say they "needed" to move in — perhaps they'd lost their job or couldn’t make ends meet.
"If you are working one or two low-wage jobs and you are spending a lot of time with somebody, it certainly doesn't seem to make a lot of economic sense to maintain two separate apartments," Sassler said.
And baby makes three
Moving in due to necessity rather than desire may be a problem — particularly if that necessity comes in the form of an unexpected pregnancy.
One study, published in 2009 in The Annals of the American Academy of Political and Social Science by Princeton researcher Sara McLanahan, found that among low-income mothers, only 16 percent of women who married their baby's father before or after the baby's birth were still married to him by the baby's fifth birthday. And women who get pregnant and hurry to marry the father before the baby is born (in a "shotgun wedding") are more likely to divorce than women who marry after the baby's birth, according to research done by Sassler and others.
Moving in together in response to an unwanted pregnancy is similarly shaky: People who move in together after conceiving a child are three times more likely to split by their child's third birthday than people who marry after an unplanned pregnancy, according to a June 2012 paper in the Journal of Marriage and Family.
"Getting married at a young age just in response to an unintended pregnancy is not a good step if you're interested in marital stability," said Kristi Williams, an Ohio State University sociologist who studies the consequences of unwed births on women's health.
In that sense, welfare programs that encourage single moms to marry may not be effective, especially because cycles of marriage and divorce may be worse for kids than growing up in a stable, single-parent home, Williams told Live Science.
"It may end up producing worse outcomes, if those unions end in divorce," Williams said.
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