Premenstrual dysphoric disorder (PMDD), a severe form of premenstrual syndrome (PMS), is a set of physical or mood-related symptoms that occur before your menstrual period each month. Symptoms begin about 1 to 2 weeks before your period starts and go away in the first few days of your period. With PMDD, these symptoms interfere with your life. They may affect your relationships, work, or school.