Premenstrual syndrome (PMS) is a collection of unpleasant symptoms that begin each month during the luteal phase of the menstrual cycle and end with the onset of menstruation. Common symptoms include hot flushes, cramps, bloating, acne, mood swings, headaches, anxiety, and more. Premenstrual dysphoric disorder (PMDD) is when the symptoms are severe, particularly those related to mood.