Premenstrual dysphoric disorder (PMDD) is a severe form of premenstrual syndrome (PMS). Like PMS, premenstrual dysphoric disorder follows a predictable, cyclic pattern. Symptoms begin in the late luteal phase of the menstrual cycle (after ovulation) and end shortly after menstruation begins. On average, the symptoms last six days but can start up to two weeks before menses, meaning symptoms can be felt for up to three weeks out of a cycle. Severe symptoms can begin and worsen until the onset of menstruation, with many not feeling relief until a few days after menstruation ends. The most intense symptoms occurring in the week and days leading up to the first day of menstrual blood flow. The symptoms usually cease shortly after the start of the menstrual period or a few days after it ending. The onset of symptoms only during or around the luteal phase is key for diagnosing a woman with PMDD rather than any other mood disorders.