#992 - Dr Sarah Hill - The Period Brain: How Hormones Change Women’s Behaviour
In this episode of Modern Wisdom, Dr. Sarah Hill and Chris Williamson explore how hormones affect women's behavior throughout the menstrual cycle. They discuss how estrogen and progesterone influence everything from mate selection and social motivation to energy levels and relationship security. The conversation covers the biological mechanisms behind these changes and explains how different phases of the menstrual cycle trigger specific behavioral adaptations.
The discussion also examines how hormonal birth control affects women's experiences by creating a stable hormonal state that differs from natural cycles. Hill and Williamson address the gaps in hormone research, particularly how excluding women from studies or only examining them during specific cycle phases has led to misconceptions about hormones' impact on women's physiology and behavior.
This is a preview of the Shortform summary of the Sep 11, 2025 episode of the Modern Wisdom
Sign up for Shortform to access the whole episode summary along with additional materials like counterarguments and context.
1-Page Summary
Biology and Evolutionary Functions of Menstrual Cycle
Sarah Hill and fellow researchers explore how the menstrual cycle influences women's attraction mechanisms and pregnancy preparation. During the first half of the cycle, high estrogen levels enhance women's ability to attract and select potential mates. Hill notes that women experience increased energy, sexual desire, and heightened ability to detect subtle differences in potential mates through scent and appearance.
In the cycle's second half, Hill explains that progesterone dominates, triggering behaviors that support potential pregnancy. Women's bodies increase calorie needs, shift to energy conservation, and demonstrate heightened sensitivity to social and relationship threats. This phase is marked by increased caution and a stronger focus on relationship security.
Psychological and Behavioral Impacts of Menstrual Hormones
According to Hill and Chris Williamson, hormonal fluctuations throughout the menstrual cycle serve adaptive functions. During high-estrogen phases, women experience increased social motivation and sexual desire, with enhanced ability to evaluate potential mates. Post-ovulation, when progesterone rises, women's focus shifts to safety and security, with decreased social motivation but increased desire for emotional connection.
Influence of Birth Control on Women's Experiences
Hill explains that hormonal birth control creates a stable hormonal state by maintaining high synthetic progesterone and low estrogen levels, effectively suppressing natural fluctuations. This can lead to mood disorders and reduced relationship satisfaction. The researchers note that hormonal birth control can simulate a perpetual state similar to the latter half of the menstrual cycle, potentially affecting women's sexual decisions and emotional experiences.
Biases and Gaps in Women's Hormone Research
Hill and Williamson highlight significant research biases in women's hormone studies. They note that researchers often exclude women from studies or only examine them during low-hormone phases. This "bikini medicine" approach, as Hill describes it, has led to misconceptions about hormones' impact on women's physiology and behavior. The experts argue that dismissing women's hormonal experiences has resulted in inadequate treatment across medical, professional, and social contexts.
1-Page Summary
Additional Materials
Actionables
- Track your menstrual cycle to plan social and professional engagements around your hormonal phases. By understanding when you're likely to feel more energetic and socially motivated, you can schedule important meetings, dates, or social events during the first half of your cycle. Conversely, save tasks requiring focus and less social interaction for the second half when you might prefer solitude and concentration.
- Create a personalized wellness plan that aligns with your cycle's nutritional and emotional needs. Increase your calorie intake slightly in the second half of your cycle when your body's energy demands rise, and incorporate foods rich in magnesium and vitamin B6 to support mood and energy. Additionally, plan for more self-care activities post-ovulation to cater to your need for emotional connection and security.
- Advocate for inclusive research by participating in studies focused on women's hormonal health or supporting organizations that fund such research. You can contribute to a broader understanding of women's health by volunteering for studies or donating to research initiatives, helping to close the knowledge gap and improve treatments and awareness of women's hormonal experiences.
Get access to the context and additional materials
Biology and Evolutionary Functions of Menstrual Cycle
Sarah Hill and other researchers delve into the nuances of the menstrual cycle, exploring its functions in relation to attraction and preparation for potential pregnancy.
Functions of Menstrual Cycle: Attraction & Pregnancy Prep
The purpose of the menstrual cycle is deeply rooted in reproductive functions, governing the way women interact with potential mates and how they prepare for the possibility of pregnancy.
During the First Half of the Cycle, High Estrogen Optimizes Women's Attraction Mechanisms
During the first half of the menstrual cycle, as estrogen levels rise, women experience increases in energy and sexual desire. Hill points out that this period is when women feel their most attractive and are best able to differentiate between potential mates. Research supports these observations through various studies: women at high fertility have shown a lower threshold for noticing subtle differences in [restricted term] levels through scent and appearance.
The evidence for this heightened period of attractiveness is not just subjective; tangible measures such as the increased earnings by strippers not on birth control during their high fertility phase underscore the power of natural attraction mechanisms. Moreover, men have been found to prefer the scent of women when they are at high fertility, emphasizing the deep biological interplay of attraction. Men exposed to these scents exhibit higher levels of hormones like [restricted term] and cortisol, illustrating an innate physiological response.
Thus, the first half of the cycle, dominated by estrogen, marks a period when women are more appealing to men and more selective of them, preparing their bodies for possible conception through a fine-tuned biological interplay of hormones and behaviors.
During the Cycle's Second Half, When Progesterone Is High, Women Optimize For Potential Pregnancy, Including Increased Calorie Intake, Energy Conservation, and Heightened Sensitivity to Social and Relationship Threats
Hill expands on the evolutionary functions during the latter half of the cycle, when progesterone takes precedence. The release of progesterone after ovulation signals emotional sensitivity and risk aversion, akin to a sensitive smoke detector, which may steer the brain and behaviors in pregnancy-favorable directions. This phase commonly triggers behaviors aligned with safety, protection, and energy conservation—key factors to foster a safe environment for potential pregnancy.
During this phase, women's basal metabolic rate rises, leading to a need for an additional intake of calories (around 150 to 200) per day. The body undergoes a shift from a pro-inflammatory to an anti-inflammatory immune response and an increase in body t ...
Here’s what you’ll find in our full summary
Biology and Evolutionary Functions of Menstrual Cycle
Additional Materials
Actionables
- Track your menstrual cycle to optimize social and professional interactions by marking days of high fertility when you might feel more confident and days of high progesterone when you might prefer quieter activities. For example, schedule important meetings or social events during the first half of your cycle and reserve the second half for tasks that require less social interaction.
- Adjust your diet to support your body's needs throughout the menstrual cycle by increasing calorie intake during the luteal phase and opting for energy-boosting foods during the follicular phase. You could prepare meal plans that include more complex carbohydrates and proteins during the luteal phase to accommodate the increased basal metabolic rate.
- Create a personal ...
Related Shortform Content
Get access to the context and additional materials
Psychological and Behavioral Impacts of Menstrual Hormones
Sarah Hill and Chris Williamson delve into how menstrual hormones influence women’s psychology and behavior, suggesting that these changes have functional and adaptive benefits.
Women's Psychological and Behavioral Shifts Reflect Biological Functions
High Estrogen Boosts Motivation for Social and Sexual Activities
Hill explores the effects of estrogen on women's brains and behavior, suggesting that when estrogen is high and rising, it leads to positive changes in behavior and increased motivation for social and sexual activities. As estrogen gets released during the first part of the cycle, it increases women's energy and desire for sex, which reflects their biological need to reproduce at this stage. She mentions that high estrogen levels cause neurons to sprout new dendritic spines, making the brain more sensitive and attuned to the environment.
During this time, women are more outgoing, have a higher sex drive, and experience an increase in sexual desire, as noted by Chris Williamson. This heightened brain sensitivity translates to a greater ability to discern subtle differences in prospective mates, with attention to both scent and visual cues. This drive aligns with the biological function of optimizing partner selection when the likelihood of conception is high.
High Progesterone Post-Ovulation Leads To Safety Focus, Decreased Social Motivation, and Increased Threat Sensitivity
Hill poses that the negative feelings women have in the second half of their cycle, when progesterone is high, may be related to a focus on safety, decreased social motivation, and increased threat sensitivity. Progesterone makes the amygdala more sensitive to threats and is associated with a tendency to stay home, and a heightened ability to perceive danger signals. In the post-ovulation phase, women experience a shift toward focusing on safety, conserving energy for potential pregnancy, and a decreased motivation for socializing. Sex during the luteal phase tends to be about connecting with a partner, which likely aligns with safety and pair bonding.
Hill notes the heightened relational insecurity and the stronger desire for sex, particularly among women who sense a care gap in their relationship. She suggests that the increased sexual desire during the luteal phase is more about seeking connection and ensuring the partner’s commitment. The hosts discuss that sex during the second half of the menstrual cycle could lead to an increased likelihood of emotional bonding, which aligns with a heightened focus on safety and pair bonding.
Cyclical Shifts in Women's Psychology and Behavior Had Adaptive Functions
The hosts discuss tha ...
Here’s what you’ll find in our full summary
Psychological and Behavioral Impacts of Menstrual Hormones
Additional Materials
Counterarguments
- The relationship between hormone levels and behavior is complex, and while there may be general patterns, there is significant individual variation in how women experience their menstrual cycles.
- Some research suggests that the influence of menstrual hormones on cognition and behavior may not be as strong as once thought, and non-hormonal factors such as cultural expectations and individual differences play a significant role.
- The evolutionary psychology perspective may oversimplify the adaptive reasons for these behaviors, not accounting for the multifaceted nature of human social interactions and the modern context in which they occur.
- The idea that workouts may be less effective for building muscle during the luteal phase could be challenged by studies showing that exercise performance and muscle adaptation do not necessarily align with menstrual cycle phases.
- The emphasis on biological functions may inadvertently reinforce gender stereotypes or be used to justify them, which is a social concern rather than a scientific one.
- The concept of increased emotional bonding during the luteal phase due to sexual activity is not universally supported by empirical evidence and may va ...
Actionables
- Track your menstrual cycle using a calendar app to plan social activities and self-care around your hormonal fluctuations. By marking the days when estrogen is likely to be high, you can schedule events that require high energy and social interaction, such as parties or networking events. Conversely, during the luteal phase, when progesterone rises, you might plan more solitary activities or self-care routines that focus on safety and rest, like a quiet evening at home or a gentle yoga session.
- Create a personalized workout plan that aligns with your menstrual cycle phases. During the high-fertility phase, when your body is primed for muscle building, incorporate strength training and high-intensity workouts. As you enter the luteal phase, when workouts may be less effective for muscle building, shift your focus to lighter activities such as walking or pilates, which can help prevent burnout and accommodate the need for more rest.
- Adjust your diet throughout the menstrual cycle to support your body's ...
Get access to the context and additional materials
Influence of Birth Control on Women's Experiences
The discussion led by Sarah Hill and Chris Williamson delves into how hormonal birth control affects women's hormonal states and, subsequently, their overall experiences and behavior.
Hormonal Birth Control Suppresses Natural Hormonal Fluctuations
Stable Hormonal State Eliminates Behavioral Changes
Hill explains that the birth control pill shuts down the natural flux between estrogenic and progesterone states, creating a stable hormonal state by maintaining a relatively high level of synthetic progesterone and a low level of estrogen every day. This misplaced mimicry of progesterone by progestins prevents natural estrogen production and ovulation, leading most women to feel a noticeable difference, often described as feeling awful. The discussion highlights that the synthetic progestins in hormonal birth control, differing from natural progesterone, act differently in the body and often lead to a flatlining state that suppresses natural hormonal fluctuations and behavioral changes associated with them.
As a result, women on the pill typically do not experience the "authentic self" moments tied to regular hormonal cycles, such as the estrogen surge that increases feelings of well-being and attractiveness. Moreover, because women on hormonal birth control do not ovulate, they miss out on the natural "hotness surge" of heightened estrogen levels.
Hormonal Birth Control Linked To Mood Disorders, Reduced Relationship Satisfaction in Women
Lack of Hormonal Fluctuations and Associated Psychological Experiences
Hill further discusses that hormonal birth control can simulate a perpetual state akin to the latter half of the menstrual cycle, characterized by decreased sexual desire and a lesser preference for masculinized traits in male partners. This constant hormonal state and the absence of natural estrogen peaks can affect women’s mood and possibly lead to reduced relationship satisfaction. Hill contemplates the impact of oral contraceptives on women's sexual decisions, suggesting that the suppression of menstrual cycle-related psychological experiences may also affect emotional states linked to non-conceptive sex.
Additionally, Williamson brings up that oral contraceptives raise the risk of depression by 40% in teens and women, and Hill notes that in Europe, hormonal birth control's mood-related side effects are recognized, whereas the American medical community has been slower to accept and communicate these risks to patients.
The link between hormonal birth control and mood disorders is further supported by the lack of allopregnanolone, a calming neurosteroid that promotes mental health and mood stability, in users of the pill. This is because synthetic progestins do not break down to produce allopregnanolone, resulting in lower levels ...
Here’s what you’ll find in our full summary
Influence of Birth Control on Women's Experiences
Additional Materials
Clarifications
- Allopregnanolone is a neurosteroid that plays a role in promoting mental health and mood stability. It is derived from progesterone and has calming effects on the brain. Synthetic progestins in hormonal birth control do not break down to produce allopregnanolone, potentially leading to lower levels of this beneficial neurosteroid. Reduced levels of allopregnanolone have been associated with mood and anxiety disorders.
- The "hotness surge" is a term used to describe the increase in feelings of attractiveness and well-being that can occur during the menstrual cycle when estrogen levels peak. This surge is often associated with heightened confidence and a sense of vitality that some women experience around ovulation. It is a natural phenomenon tied to hormonal fluctuations and can influence a woman's perception of herself and her interactions with others. This surge is linked to the body's preparation for potential conception and plays a role in reproductive behaviors and mate selection.
- The term "authentic self" moments tied to regular hormonal cycles refers to the natural fluctuations in hormones, like estrogen and progesterone, that occur during a woman's menstrual cycle. These hormonal changes can influence emotions, behaviors, and perceptions, leading to shifts in mood and self-perception. Women may feel more connected to their true selves during specific phases of their cycle when certain hormones, like estrogen, peak, influencing feelings of well-being and confidence. The absence of these hormonal fluctuations, as seen in women using hormonal birth control, can impact how they experience and connect with their emotions and sense of self.
- Hormonal birth control can suppress women's fertility signals by preventing ovulation, which is a key indicator of fertility. This suppression can impact not only the woman's reproductive abilities but also potentially affect hormonal interactions between partners. The absence of natural hormonal fluctuations due to birth control can interfere with the signaling mechanisms related to fertility, potentially influencing broader social and psychological a ...
Counterarguments
- Hormonal birth control provides a predictable hormonal environment, which some women prefer for managing symptoms of hormonal fluctuations like PMS or PMDD.
- The "authentic self" concept is subjective and can vary greatly from person to person; some may feel their authentic self is better represented when they are not experiencing the mood swings associated with their cycle.
- The link between hormonal birth control and mood disorders is complex and may not be solely causative; other factors such as pre-existing mental health conditions and lifestyle can also play significant roles.
- The increased risk of depression associated with oral contraceptives may be influenced by confounding variables, and not all studies have found a direct causal relationship.
- The benefits of hormonal birth control, such as reduced risk of certain cancers, regulation of menstrual cycles, and alleviation of endometriosis symptoms, can outweigh the potential mood-related side effects for many women.
- The impact of hormonal birth control on relationship satisfaction is not universally negative, and some couples may experience improved satisfaction due to the reduced anxiety over unintended pregnancy.
- The suppression of fertility signals is not necessarily a negative outcome for all women, especially those who are not s ...
Get access to the context and additional materials
Biases and Gaps in Women's Hormone Research
Experts Sarah Hill and Williamson highlight the biases and gaps in women's hormone research, emphasizing the need for a better understanding of sex differences and a shift in how society and science approach women's hormonal health.
Research on Sex Differences Biased: Women Often Excluded or Studied In Low-hormone Phases
Hill laments the approach taken by many researchers to the study of women, often excluding them from research or studying them only during the low-hormone phases of their menstrual cycles. Historically, researchers have favored studying men because it was simpler—men don't have the complication of pregnancy or hormonal cycles to consider.
Male and female bodies were traditionally assumed to be the same apart from reproductive functions, leading to a "bikini medicine" approach where the only differences considered were the organs covered by a bikini. Women, when included in research, were typically studied during the first nine days of their cycle when hormone levels are low, which researchers believed would make their physiology more comparable to that of males. This has resulted in a misconception that hormones do not have a significant impact on women, as most research ignores the full cascade of physiological changes that occur throughout a woman's cycle.
Hormonal Changes' Impact on Women's Physiology, Psychology, and Behavior
Sarah Hill points to robust evidence that hormonal changes lead to physical and psychological changes in women, including an increase in sexual motivation during high fertility when women report feeling and smelling "sexier." These widespread hormonal changes can also affect caloric needs, workout recovery, and muscle-building capacity. Hill emphasizes the different versions of themselves that women experience during their menstrual cycle and criticizes the broad range considered 'normal' for hormonal levels, which complicates the understanding of hormonal experiences.
Dismissing Women's Hormonal Experiences as Irrational Devalues Sex Differences
Hill and Williamson discuss the societal trend of denying the importance of biological sex and hormonal differences, labeling the approach as "soft bigotry of male expectations." Hill argues that ignoring sex differences has led to women being mismanaged in science and medicine, which has far-reaching consequences for women’s treatment across various societal spheres, including work, medicine, and society.
Implications For Women's Treatment in Work, Medicine, and Society
Hill highlights significant sex differences in conditions like depression and autism spectrum disorder and finds it absurd that studies on these conditions often fail to look for sex differen ...
Here’s what you’ll find in our full summary
Biases and Gaps in Women's Hormone Research
Additional Materials
Actionables
- You can track your own or a partner's hormonal cycle to better understand mood and health patterns by using a cycle tracking app and noting daily physical and emotional states. This personal data can reveal trends and inform discussions with healthcare providers for more personalized care.
- Start a book club focused on literature that explores sex differences in health and behavior to raise awareness and foster informed conversations. Choose books that delve into the science of sex differences and their implications, and meet regularly to discuss insights and experiences.
- Encourage open conversations with friends ...
Get access to the context and additional materials
Create Summaries for anything on the web
Download the Shortform Chrome extension for your browser
