PMDD is generally thought to be an extreme form of PMS (premenstrual syndrome). Upwards of 75% of women have some physical and/or emotional symptoms before their periods that could be considered PMS. For most women, PMS symptoms cause only mild to moderate discomfort and require little or no treatment. Far fewer women, perhaps 3% to 8%, have severe disabling, disruptive premenstrual symptoms that include depression, anxiety and irritability. These women have a treatable medical disorder known as premenstrual dysphoric disorder or PMDD.