Many women experience feelings of tension, anger, fatigue and depression just before and during the first days of their menstrual period. This is called premenstrual syndrome (PMS) and is caused by the changes in hormone levels. In most women with PMS, symptoms will not be severe enough to require treatment, but some will need to discuss their symptoms with a doctor. The most severe form of PMS is called premenstrual dysphoric disorder (PMDD). There are a range of effective therapies for PMS.