Current research on PMDD suggests that it may have a genetic cause, but there is currently insufficient evidence to support this theory fully. Anyone who has periods could experience symptoms of PMDD. The onset of PMDD can be triggered by a period of severe hormonal fluctuation, eg. first period, post pregnancy, or during peri-menopause.
People with PMDD are abnormally sensitive to changes in oestrogen and progesterone the hormones which affect ovulation which is why symptoms can often get worse around this point in your cycle.
You can get more support for PMDD here