Premenstrual symptom (more commonly referred to by its acronym, PMS) affects at least 85 percent of women, according to an estimate provided by the American College of Obstetricians and Gynecologists. Nobody quite knows what causes PMS, but scientists have a range of theories for why we experience symptoms like irritability and bloating. For one, hormonal changes during the menstrual cycle mess with two important neurotransmitters—GABA and serotonin—that help regulate mood. Meanwhile, bloating might stem from changes in a kidney hormone that affects water retention.

Learn more about the chemistry behind the common—yet dreaded—condition in the American Chemical Society’s latest Reactions video.

Banner image: iStock

[h/t Reactions]

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