Logic dictates that a trial run of shacking up together should increase the odds of a stronger relationship. Picture: PxHere

After decades of research, experts still can’t decide if living together before marriage leads to divorce. They’ve even coined a phrase for it: The “cohabitation effect”.

Logic dictates that a trial run of shacking up should increase the odds of a stronger relationship, right? So why is it that cohabitation has been linked to divorce? Is it a nasty rumour or is there concrete proof to support the claim?

It goes back to 1992, when a landmark study suggested a link between living together and divorce.

Called “Cohabitation and Marital Stability: Quality or Commitment?”, Elizabeth Thomson and Ugo Colella’s findings were published in the Journal of Marriage and Family.

Using data from 1987 to 1988, they found that couples who cohabitate before marriage reported lower quality of marriages, lower commitment to the institution of marriage and greater likelihood of divorce than couples who did not.

Subsequently, a flurry of studies sought to investigate why this may be the case.

Then a study published in the same journal in 2012 concluded that “since the mid-1990s, whether men or women cohabited with their spouse prior to marriage is not related to marital stability.”

Why the inconsistencies?

Data taken from Dr Nicole Hiekel’s study. Study screenshot

While chatting to US publication The Atlantic, Galena Rhoades - a psychologist at the University of Denver - had a few theories.

She said it’s hard to study divorce in ways that are useful and accurate because data takes so long to collect.

For example, she noted “if we study a cohort of people who got married 20 years ago, by the time we have the data on whether they got a divorce or not, their experience in living together and their experience of the social norms around living together are from 20 years ago”.

Now a new study from The University of Cologne may be closer to understanding the link between cohabitation and divorce.

Led by Dr Nicole Hiekel from the Institute of Sociology and Social Psychology, researchers found that nine out of 10 people who move in with their first or second partner either get married or separate within five years.

“Our study suggests that despite the increasing popularity of unmarried cohabitation and the rise in partnership instability, there is not a loss in the importance of marriage,” said Hiekel.

The study analysed the relationship biographies of around 2 500 women and men, aged 35 - 45. It is now considered normal to live with multiple partners during a lifetime.

However, the researchers suggested that living with your first or second partner creates a make or break situation.

While 90 percent get married or break up, you’re actually twice as likely to tie the knot than finish the relationship.

The findings were published in the Journal Demographic Research.

Data and findings aside; can we not just decide on one reasonable conclusion?

Dr Justin Lehmiller, a sex researcher at the Kinsey Institute, breaks it down in simpler terms.

“On average, people who cohabitate tend to move in together at a younger age. So maybe it’s age - not premarital cohabitation - that explains the higher divorce risk,” he wrote on his blog.

He went on to explain that when you compare people’s divorce risk based on the age at which they began “acting married”, instead of the age at which they actually got legally married, the “cohabitation effect” disappears.

“In short, it seems that what’s going on here is that age - not cohabitation - is the true risk factor for divorce, meaning that couples who move in together or get married at a very young age have the highest risk of later separation,” Lehmiller said.