Premenstrual dysphoric disorder (PMDD) is an illness associated with the luteal phase of the menstrual cycle. It is characterized by severe irritability, anxiety and anger. It is similar to premenstrual syndrome (PMS), but differs from it in severity and in that it requires treatment, because it interferes in a woman's ability to function in her environment. It has been proposed as a disorder requiring further study by the American Psychiatric Association in the DSM-IV-TR.