It’s sort of a given that women get, shall we say, somewhat emotional at a
certain time of the month. Guess what? PMS may be a myth. New Zealand
researchers found that just 15 percent of women report their moods get worse
when their cycle is about to start. It’s speculated that the concept of PMS
started as a sexist idea about women’s changing moods from a time when most
physicians were male.
Source: Time, 10/22/12