The Seven Year Itch was a play written in 1952 that was later turned into a movie starring Marilyn Monroe. In the movie, Monroe -- a young single woman -- moves into an apartment building and becomes the focal point of interest for another resident, a man who becomes obsessed with her while his wife and son are off for the summer.

Over the decades, the title has become ensconced in the media and as a term sometimes used by psychologists and family therapists as a mantra for when marriage often loses luster for many couples. Although the expression is often used loosely, data from the Census Bureau might give it a bit of solid credence going forward. The median time from marriage to divorce in the United States, say bureau researchers, is right around the seven-year mark.

Bottom line: Stresses build. They are broad-based -- kids, finances, careers, aging family members, differences concerning friends, hobbies and vacations -- and take a few years to manifest. Some couples work them out.

Some don't and, after dealing with them for a few years, separate and sometimes divorce. Often, that process takes seven to eight years.

"[It] is rarely the case of a happily married person who discovers after seven years that Marilyn Monroe has just moved in downstairs," says one sociology and public policy professor.

Another person focused on the seven-year reference-- a family counselor -- says that issues unrelated to a couple's relationship often close in on them and become overwhelming.

"What ends up happening is that there's not enough romance," he says, adding that, "Sometimes, it's a miracle they last seven years."

Related Resource: Boston Globe, "The magic number when magic's gone" July 29, 2011