What is PMS? PMS, premenstrual syndrome, is the name given to the disorder characterized by a set of hormonal changes that lead to disruptive emotional and physical symptoms in a significant amount of women. The symptoms happen monthly, usually within one or two weeks before menstruation. It is estimated that there's approximately 40 million sufferers of PMS. Of that 40 million, more than 5 million require medical treatment for their behavioral and mood changes. Symptoms seem to worsen as menses (menstruation) approaches and lessens after the your period. Symptoms of PMS occur before the first day of a woman's period . Not