PMS and PMDD share timing but differ sharply in severity and clinical definition. This explainer breaks down DSM-5 criteria, the luteal-phase serotonin connection, and a two-cycle tracking method to help you know when to seek care.
Your cycle is driven by four distinct hormonal phases — each shifting estrogen, progesterone, LH, and FSH in ways that directly shape your energy, mood, and focus. Here's the science behind what you feel and why.