Reasons Women Need Periods: The Role of the Menstrual Cycle in Brain Health & Development

Reasons Women Need Periods: The Role of the Menstrual Cycle in Brain Health & Development

Earlier this year, we started a “Reasons Women Need Periods” series putting a spotlight on how women’s periods play a crucial role in other elements of women’s health. We talked about the importance of endogenous (i.e., naturally occurring) hormones and healthy cycles for immune system maturation, bone health, and heart and blood pressure regulation. Today we’re turning to the biggest and baddest organ of all—the brain.

Our noggin uses over 20% of our energy, making it the most “expensive” organ we have. And, you guessed it, our reproductive hormones (especially estrogen and progesterone) have really important effects on the brain. Brain health is another reason why you need a period—and therefore ovulation, and the healthy hormone production that makes your cycle possible.

Your brain and your hormones need each other

The first important thing to note is that steroid hormones (primarily estrogen and progesterone) are synthesized in the central and peripheral nervous system. This means they cross the blood-brain barrier and have organizational effects on the brain. Estrogen generates plasticity in the brain and improves cognitive function while progesterone regulates glial cells and promotes mood stabilization [1]. Before you think about these two hormones as independent players, they are anything but. If the effects of these hormones are not experienced in a balanced and cyclical way, the neuroprotective factors they are supposed to provide vanish.

In the first portion of our cycle (the follicular phase), estrogen is king. Or should I say—queen. As the dominant follicle in your ovary gears up for ovulation and grows, it produces increasing amounts of estrogen. This estrogen increases serotonin receptor levels as well as dopamine synthesis. This boils down to an increase in neuron excitability. These stimulated neurons increase structural plasticity of dendritic spines in the hippocampus, amygdala, and prefrontal cortex. Neuron excitability often translates to general feelings of an upbeat mood, increased energy levels, and improved verbal and lingual skills.

In the second portion of our cycle (the luteal phase), progesterone sweeps in and takes the stage. Progesterone is estrogen’s foil character. Instead of stimulating brain cells, it heals and maintains them by inhibiting dopamine-induced glutamate release. In this therapeutic phase, women often report mellowness in mood, decreased anxiety, and even more maternal tendencies. This is all thanks to GABA, the most inhibitory neurotransmitter in the brain. Progesterone (and allopregnanolone, which comes from progesterone) potentiates GABAergic synapses [2]. If there’s no progesterone, there’s no GABA. And interestingly, GABA has been shown in early studies to be an effective treatment for premenstrual dysphoric disorder (PMDD) [3].

Teens need their cycles for proper brain development

Have you ever wondered why teenagers and young adults seem to make more brash decisions and seem less grounded with risk assessment? It’s because quite literally, their brains—or more accurately, their prefrontal cortices—can’t process risk until they have fully matured. This full maturation usually occurs in the mid-twenties. Exposure to endogenous and balanced hormones (which occurs through regular ovulation and menstruation) throughout the teenage and young adult years helps develop and protect the brain. Without ovulation, the brain doesn’t have the same chance to mature. And even better, maturation under healthy endogenous hormones can help retain brain plasticity better for women after menopause.

Brain fog and depression: Birth control’s effects on the brain

You may think that the hormones in hormonal contraception have the same effect on brain health as endogenous hormones do. Unfortunately, the synthetic alternatives of estrogens and progesterone found in birth control have been shown to decrease serotonin concentrations and increase hepatic sex hormone binding globulin (SHBG). In effect, this makes your naturally occurring sex hormones harder for your body to utilize.

This could be also why women on hormonal contraception have been shown to have a decreased hypothalamus, “which helps regulate essential bodily functions including body temperature, mood, appetite, sex drive, sleep cycles and heart rate [4].” A smaller hypothalamus is connected with increased irritability and depression symptoms. Additionally, “synthetic estrogen and progestins in OCs may decrease cortical thickness bilaterally in the lateral orbitofrontal cortex, and in the posterior cingulate cortex” which can permanently alter certain pathways of cognitive function in women [5].

It’s well documented that the pill (and any of its relations, including the patch, the vaginal ringthe implant, the shot, and the hormonal IUD) comes with an increased risk of depression and mood disorders. Additionally, many women report “foggy brain” as a side effect of hormonal birth control. Some women don’t realize the symptom of brain fog until they get off birth control, and many women report feelings of “seeing in color for the first time” after returning to their cycles post-birth control. This is all related to the way the endocrine system acts on the brain. When you look at the bigger picture of how these synthetic hormones not only alter brain organization, but also rob the brain of exposure to endogenous hormones, these risks start to make sense.

You’re not crazy—your thoughts and feelings are very much tied to your hormones!

The Pill and your stress response—or lack thereof

Another glaring contrast in pill-taking brains as opposed to non-Pill-taking brains is the stress response, or rather the lack thereof.

As the author of the 2019 book This is Your Brain on Birth ControlDr. Sarah Hill puts it:

“For almost three decades now, researchers have been documenting that women on the birth control Pill lack the cortisol response to stress. Pill-taking women exhibit higher than average levels of total cortisol, high levels of corticosteroid binding globulins (CBGs), and dysregulated responses to exogenously administered cortisol. This is significant because these patterns are typically only observed when the body becomes so overwhelmed with cortisol, signaling that it has no choice but to shut the signal down, altogether.”

“We should all be alarmed by the fact that the stress hormone profiles of women who are on the birth control pill look more like those belonging to trauma victims than they do like those belonging to otherwise healthy young women [6],” Hill exhorts.

When women’s bodies naturally ovulate and menstruate, women’s brains are enabled to mature, improve, and maintain cognitive function, and even protect their future neuroplasticity. When they take synthetic hormones that disrupt these natural reproductive processes, these brain developments are inhibited.

So, do you need a period? The answer lies in how much we care about women’s overall health as the interconnected ecosystem that it is—where hormone health affects heart health, immune system health, bone health, and now we can add brain health to the list. Since ovulation and menstruation have lifelong effects on cognitive function—which can affect how you interact with yourself and others in the world—there is a compelling case that these are vital aspects of women’s health.


[1] Del Río J, Alliende M, Molina N, Serrano F, Molina S, Vigil P. Steroid Hormones and Their Action in Women’s Brains: The Importance of Hormonal Balance. Front Public Health. 2018;6. doi:10.3389/fpubh.2018.00141

[2] Boero G, Porcu P, Morrow A. Pleiotropic actions of allopregnanolone underlie therapeutic benefits in stress-related disease. Neurobiol Stress. 2020;12:100203. doi:10.1016/j.ynstr.2019.100203

[3] Hantsoo L, Epperson C. Allopregnanolone in premenstrual dysphoric disorder (PMDD): Evidence for dysregulated sensitivity to GABA-A receptor modulating neuroactive steroids across the menstrual cycle. Neurobiol Stress. 2020;12:100213. doi:10.1016/j.ynstr.2020.100213

[4] Study finds key brain region smaller in birth control pill users. ScienceDaily. Published 2020. Accessed November 11, 2020.

[5] Petersen N, Touroutoglou A, Andreano J, Cahill L. Oral contraceptive pill use is associated with localized decreases in cortical thickness. Hum Brain Mapp. 2015;36(7):2644-2654. doi:10.1002/hbm.22797

[6] Hill S. This Is Your Brain On Birth Control. New York, NY: Avery; 2019.

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