Hollywood and Seven Year Itch

The term 'Seven Year Itch' can be traced back to the 1955 Hollywood flick starring Marilyn Monroe and Tom Ewell (remember her famous wind blown halter dress?) . The movie mentions a book that says many men have extra-marital affairs after seven years of marriage — terming it the"7-Year Itch". Ever since then, with her halter gown, the term too became a rage and is disturbingly seen in most marriages .

Kate Winslet and Sam Mendes were the latest to fall under the spell of the so-called '7-year-itch' when they filed for divorce last year.

What is behind this inexplicable phenomenon? Is it astrology, numerology or even psychology? Why do couples decide to go their separate ways after seven long years of being together? Is it something that occurs to them all of a sudden or is it the culmination or an eventual surge of all those pent-up emotions that have been lying dormant like a volcano for years? If the latter sounds more plausible, then it's more likely to be a woman's initiative.