Many women in their late 30s and 40s are surprised when anxiety shows up out of nowhere — even when life is stable and nothing is “wrong.” This is one of the most overlooked symptoms of perimenopause. Fluctuating estrogen and progesterone directly affect brain chemicals like serotonin, GABA, and adrenaline, creating a constant sense of alertness. In this article, we break down the science behind perimenopause anxiety and give you evidence-based strategies to feel grounded, calm, and back in control.