Premenstrual Syndrome (PMS) is a set of physical and emotional symptoms that many women experience around the time of their menstrual cycle. Mood swings are one of the most common PMS symptoms and it is estimated that between 30 to 40 percent of menstruating women experience some type of mood-related symptom during this time. The symptoms can range from feeling irritable or having a short temper, to feeling overwhelmed with sadness or anxiety.