To determine if there's something suspicious about the seventh year of marriage, researchers have turned to statistics about marital length and surveys about marital satisfaction. In the United States, the median duration of marriages that end is just over seven years, which would seem to support the idea of a seven-year itch.
But while seven years is a median marker for marriages in the United States, researchers have noted that a significant number of marriages in this country dissolve after just two, three or four years. A 2007 study found that couples who had been married less than three years were significantly happier than the ones that had been married between four and six years [source: Roberts]. In 1999, researcher Lawrence Kurdek found that there were two major declines in a 10-year marriage -- one at seven or eight years, which appeared to be further proof of a seven-year itch, but another one at year four [source: Berger]. Year four, Kurdek hypothesized, might be the point at which the honeymoon effect had waned, giving way to boredom with the relationship.
Anthropologist Helen Fisher has a different theory as to why the four-year mark is significant. Historically, she claims, humans gave birth every four years. We were driven, therefore, to couple up for four years -- enough time to have a child and raise it through infancy. After that, according to Fisher, men and women might have a biological drive to get bored with a relationship and seek a new partner for childbearing. By having children with more than one person, parents could increase the genetic diversity in their offspring, which increased the chances that at least one of their children would survive [source: Fisher].
Fisher also notes that marrying for romance is a relatively new phenomenon, and that we live much longer today than we used to. Perhaps, as she and other researchers have speculated, we simply aren't meant to be together for this long a lifetime. But even the researchers who have produced the most dismal statistics about marital happiness say there's a positive takeaway: If you know that boredom is a downfall of relationships at various points, then you can take the steps necessary to keep romance alive and marital dullness away. Trying new things and exploring new places with your sweetheart may be the key to ensuring that there's no itch to scratch.