Diagnosis varies. It is true that diagnosis is a somewhat arbitrary process. Someone develops a list of symptoms that appear to be part of a syndrome and names the syndrome. Different cultures will focus on different symptoms that are considered maladaptive in their culture. That said, there are very real hormonal fluctuations involved with menstruation and it is well documented that hormone changes affect mood.
I Don't. Late luteal phase dysphoria & pms are very real & characterized by a variety of symptoms including irritability, cramping, pain, & swelling. There are cultural differences in the way that people of various cultures deal with & express pain but the actual physical things that happen are the same.