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What causes premenstrual symptoms such as bloating and mood changes?

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Diagram of the menstrual cycle showing hormone levels, follicle development, and endometrial changes across 28 days. It highlights menstruation, ovulation, and the follicular and luteal phases, with labeled curves for estrogen, progesterone, FSH, and LH. — menstruation Cyclical changes during a woman's normal ovulatory menstrual cycle.

The exact causes of premenstrual syndrome (PMS), which includes symptoms like bloating and mood changes, are not yet fully established by medical research. However, the most widely accepted theories point to several contributing factors:1

Hormonal Fluctuations: The rapid decrease in estrogen and progesterone levels near the end of the menstrual cycle is closely associated with the onset of symptoms, including fluid retention (bloating) and mood changes.12
Brain Chemistry: Many researchers suspect that fluctuations in chemical transmitters in the brain—such as serotonin, which influences mood and behavior—play a significant role in the emotional symptoms of PMS.13
Other Factors: Nutritional deficiencies, particularly regarding B vitamins that affect nerve transmission, and stress are also considered factors that can influence the severity of symptoms. Additionally, some genetic mutations may increase a woman's predisposition to developing PMS.1

While the relationship between these hormonal changes and specific symptoms remains complex, these factors are the primary focus of current scientific study.12