Does Infidelity Peak After 7 Years of Marriage?

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The seven-year itch refers to the popular belief that marital bliss tends to dissipate after about seven years together. At that point, the propensity for infidelity and or divorce is thought to rise.

This idea has been in popular use since 1955 when a film titled The Seven Year Itch starring Marilyn Monroe explored the concept. But is there any truth to this concept, or is it just the stuff of Hollywood fiction? Here is a look at the data.

In terms of infidelity, research suggests that married adults are more likely to think about and commit infidelity around the seven-year mark.

Thoughts of Infidelity Rise in Intermediate Marriages

In a study published in the Journal of Sex Research, 313 Israeli adults (aged 32-33 on average) were surveyed, all of whom were heterosexual and married for at least one year. Participants were asked about their likelihood of engaging in infidelity, and researchers looked at how this was associated with the length of marriage.

Participants were divided into three groups: short (<five years), intermediate (six to 10 years), and long-term marriages (11 or more years). The group that reported the greatest likelihood of cheating was the long-term group; the short-term group reported the lowest odds, with the intermediate group falling in between. The longer a couple had been together, the more likely it was for partners to say they were thinking about cheating.

However, the pattern was a little different for men and women. Specifically, for men, the odds of cheating went up the longer the relationship went on (this is what scientists refer to as a linear effect). For women, though, the effect was curvilinear, women reported the greatest likelihood of cheating in intermediate marriages, but lower odds of cheating in short- and long-term marriages.

In short, this study suggests that both men and women appear to get the so-called seven-year itch; however, while it eventually seems to pass for women, it doesn't for men.

Of course, this study was based on self-reported likelihood of cheating, not whether people went through with it. However, data looking at actual rates of infidelity backs these findings up.

Actual Rates of Infidelity Rise in the 7th Year of Marriage

Drawing on data from a nationally representative sex survey conducted in the United States, a study published in the Journal of Marriage and Family looked at when cheating was most likely to occur in a marriage. (Note: At the time these data were collected, only heterosexual marriages were legally recognized throughout the country, so that's what the researchers focused on). The results indicated that, for women, their odds of cheating were highest in the 7th year of marriage, but decreased steadily after that. (In fact, cheating was practically non-existent among women who had been married 20-30 years.)

By contrast, men also had a high rate of cheating around the seventh year, which then decreased until about year 18, at which point it started increasing again. In fact, men who had been married 30 or more years actually had the highest odds of cheating—even higher than men who had the “seven-year itch.” This suggests that the pattern for men isn’t perfectly linear after all, with a peak in that intermediate term followed by a dip, which is followed by another increase much later.

Both men and women seem to get a seven-year itch, but men seem to get a 30-year itch as well.

Most Divorces Happen Just After the Seven-Year Mark

One final piece of evidence worth considering is when divorces are most likely to occur. US Census Bureau data indicates that the average marital length prior to a divorce is about eight years.

This lines up quite well with the aforementioned infidelity data: divorces start to peak just after the odds of cheating reach their high point.

Takeaways

A few quick caveats to these findings: First, most of the supporting data comes from studies of heterosexual couples; we can't necessarily extrapolate the data to same-sex couples. Second, the nature of the data makes it hard to distinguish between the effects of age versus generation. For example, while rates of reported cheating among older women are rare, it's not clear whether older women are cheating less or whether they're just less likely to report the behavior. To draw more concrete conclusions about how the odds of infidelity change over time, a longitudinal design would give us more confidence.

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Also, much of the research on infidelity doesn't distinguish between consensual and non-consensual non-monogamy. It seems reasonable to predict that rates of both forms of non-monogamy would increase with relationship length, but it would be useful to categorize these behaviors separately in future research because it's possible that the trends might be different to some degree.

And, finally, the big question none of these studies directly answer is why. What's so special about year seven? We can only speculate. Some argue that it's because humans just move in seven-year patterns (after all, that's the average length of time Americans keep their cars, too). However, the more parsimonious explanation is simply that the honeymoon phase has ended and differences have started to emerge. When we stop viewing our partners through rose-colored glasses, we have to decide whether our differences are intractable or if we can accept or work through them.

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