Because men know we're not allowed to diagnose this particular malady:

For the first time, scientists have pinpointed an area of the brain involved in a woman's menstrual cycle. The research, reported online this week by the Proceedings of the National Academy of Sciences, shows contrasts in activity over the course of a month and provides a baseline for understanding the emotional and behavioral changes that 75 percent of all women report experiencing before, during and after their period.

If it means I'm less likely to live with a maniac for half the rest of my life, I'm all for it!