Does Menstruation Affect the Brain? Scientists Reveal Surprising Structural Changes
New research from California scientists shows that the menstrual cycle affects the structure of the entire brain. Hormonal changes that occur every month modify both white and gray matter, as well as cerebrospinal fluid. This is the first such precise evidence that menstruation has a real effect on the anatomy of the brain, not just on how we feel.
A team of researchers led by neuroscientists Elizabeth Rizor and Viktoriya Babenko of the University of California, Santa Barbara, looked at the brains of 30 women during their natural menstrual cycles. They underwent MRI scans during three key phases of the cycle: menstruation, ovulation, and the luteal phase. At the same time, hormone levels in the blood were measured.
The research, published in 2023 in the journal Human Brain Mapping , showed that the structure of the brain changes with changes in hormone levels. Importantly, not only in areas known for their high sensitivity to sex hormones.
"These results are the first to demonstrate concurrent changes in brain white matter microstructure and cortical thickness that coincide with menstrual cycle-dependent hormonal rhythms," the study authors wrote.
Researchers have found that hormone levels affect, among other things:
the volume of gray and white matter,
cerebrospinal fluid volume,
the structure of neural connections that transmit information in the brain.
Just before ovulation, when levels of estradiol and luteinizing hormone (LH) rise, changes in white matter have been observed. This may indicate faster information flow between different parts of the brain. In turn, higher levels of follicle-stimulating hormone (FSH), responsible for egg maturation, were associated with thickening of the cerebral cortex. Progesterone, which rises after ovulation, caused an increase in the volume of brain tissue while reducing the amount of cerebrospinal fluid.
While the results are groundbreaking, it is not yet known what these changes mean in practice for everyday brain function.
"Although we do not currently report functional consequences or correlates of structural brain changes, our findings may have implications for hormone-induced changes in behavior and cognition," the researchers write.
They also emphasize that further research is needed to better understand how cyclical hormonal changes affect the psyche, memory, concentration and emotions.
The average woman will experience menstruation about 450 times in her life, yet scientific knowledge about its effects on the brain is still limited. As Rizor and Babenko’s team note:
- Cyclic fluctuations in HPG axis hormones exert profound behavioral, structural, and functional effects through their effects on the mammalian central nervous system. However, very little is known about how these fluctuations alter the structural nodes and information pathways of the human brain.
In addition, new research published in 2024 by an international team confirms that each phase of the cycle causes distinct changes in the brain, and their scale also depends on the age of the person.
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