Premenstrual Syndrome (PMS) and Premenstrual Dysphoric Disorder (PMDD) are often confused — but they’re not the same. PMS is common and can cause a range of physical and emotional symptoms, while PMDD is a severe, often disabling condition that affects mood, work, and relationships. In this post, we’ll explain the key differences, how doctors diagnose PMS and PMDD, and what treatments are available.