Theories range from hormonal and chemical to nutritional and psychological .
Women whose mothers or sisters have PMS are more likely to have it, so there may be a genetic component. A combination of genetic, physiological, and environmental factors are likely involved. The physical, emotional, and psychological changes that occur in PMS coincide with hormonal changes of the menstrual cycle. PMS may simply be a response to the declining levels of estrogen and progesterone that occur just prior to menstruation. The exact roles of the various hormones are not at all clear.