ELI5: How do menstrual cycles affect mood and emotions?

The menstrual cycle affects mood and emotions because natural chemical messengers in the body rise and fall throughout the month, which directly changes how the brain feels and reacts.

Think of your body like a house and these chemical messengers, called hormones, like the music playing in the background. The two main hormones are estrogen and progesterone. When the music changes volume, the whole mood of the house changes too.

Here is how that music changes throughout a typical month:

• The Happy Playlist (The First Half): After a period ends, estrogen levels start to climb. This is like turning on upbeat, cheerful music. During this time, a person often feels energetic, confident, and patient. Everyday chores feel easier, and laughing with friends comes naturally.
• The Sudden Silence (Right Before the Period): About a week before the next period starts, both estrogen and progesterone suddenly drop down low. This sudden drop is like the music cutting out without warning. It affects serotonin, which is the brain's "feel-good" chemical.
• The Bumpy Ride (PMS): Because the feel-good chemicals dip, everyday life can suddenly feel overwhelming. This is often called PMS (premenstrual syndrome). A spilled glass of milk that was funny last week might make someone cry today. A tiny noise might feel super annoying, or someone might feel sad and want to hide under a cozy blanket with snacks.