#992 - Dr Sarah Hill - The Period Brain: How Hormones Change Women’s Behaviour

Two books on the vagina.

Congratulations.

I think it's a little bit more complex than that.

I think it's a little more complex than that, but thank you.

Why this one?

Well, you know, actually, you know, it was the biologists in me that kind of led me to this one.

So the first book was really more about my, I ended up in a rabbit hole because of my personal experiences with the pill.

And this one, I ended up in a rabbit hole because I couldn't understand why women feel so terrible during the last last two weeks of their cycle.

You know, and from an evolutionary perspective, like it doesn't make a lot of sense for women

to all have a disorder, right?

It just doesn't make any sense because generally, if there's some sort of a trait and it's causing problems, it'll get selected out of the population.

And there's been all this really wonderful work that's been done in our field looking at, you know, the impact of estrogen and how when estrogen is high and rising across the cycle, that it does all these really amazing functional things within the human, you know within the within women's brains and then with their behavior and everything else but like

there's nothing like that about what goes on in the second half of the cycle instead it just seems like women feel terrible and so i was trying to understand why that is so like what is the deep evolutionary wisdom behind self-loathing you know that that tends to go on during the second half of the cycle and you know so like why does it happen and and is it supposed to and is there some way that we can all feel better so it was really sort of an evolutionary puzzle for me that I wanted to solve.

Like crazy to think that that's for some, maybe even most women, 50% of their life.

Yeah, it is.

It's like 50% of your life.

And it seems kind of crazy that, you know, that we would be designed in a way that we're supposed to be intentionally feeling bad.

And so I thought there had to be something else going on, right?

That it probably didn't make sense that we're just supposed to feel terrible.

What actually happens in the brain across the month?

Well, so to introduce you to to the cycle, we just have to understand that, you know, the whole purpose of having a cycle in the first place is reproduction.

And for a male to reproduce, all you have to do is one thing, right?

And that one thing is have sex.

And for a female, it's a little bit more complicated than that because we're mammals.

And that means that we need to do two things in order to successfully reproduce, right?

One is have sex.

And that means doing things like attracting partners, being able to tell the difference between high-quality and low-quality partners, wanting to have sex, looking sexy, you know, smelling sexy, finding men sexy, et cetera, et cetera, et cetera.

And there's a whole bunch of research that finds that, in fact, that's true, right?

And that all of those things tend to correlate to times in the cycle when estrogen is high and rising, an egg is about to be released, and sex can lead to conception, right?

So that's job one for reproduction if you're a human female.

Job two is implantation and pregnancy, right?

And so this is where a female body has to allow this, you know, foreign genetic material, you know, half foreign genetic material, this embryo implant, and then, of course, be able to carry it to term for nine months.

And this is the set of activities that's coordinated by our other sex hormone, progesterone.

And this is the sex hormone nobody talks about, right?

It's like we think like estrogen, and then with guys, we think testosterone.

And there's really not a whole lot of talk about progesterone.

And so I was kind of curious about like, what actually goes on during the point in the cycle when progesterone is the dominant hormone, right?

Are these things actually trying to guide our brain and behavior in a way that will help to facilitate pregnancy?

Because we find that human, like women are become very much oriented toward men and towards sex in the first half of the cycle when estrogen is high and rising.

And so I was really trying to figure out like, is there some method to our madness during the second half of the cycle when progesterone is dominant?

And might it be creating shifts in the way that we feel and experience the world that might be functional?

And might they feel a little bit dysfunctional just simply because we don't really give voice to them?

And by giving voice to them, I don't mean that we all need to sit around and talk about how we feel during the second half of the cycle.

But instead, it's this idea that, you know, the way that women have been handled by science and by medicine is that we're just like small, less hairy versions of men.

And so nobody's really given too much, paid too much attention to the fact that our hormones cycle and that what our bodies need and the way that we experience the world and even the way that we experience symptoms of chronic diseases or chronic conditions like ADHD and

things like diabetes and autoimmune disease, and that all of this might actually shift across the cycle with our shifting hormones.

And as it turns out, and as I talk a lot about in the new book, The Period Brain, is these things do change across the cycle, right?

And it turns out that women are a somewhat different version of themselves during the last two weeks of the cycle than they are during the first two weeks of the cycle.

And that a lot of the misery that we experience is the result of the fact that we've totally ignored that, right?

It's just like nobody wants to acknowledge that biological sex matters when it does.

And the result of this is that women have been absolutely mishandled by science and by medicine.

And one of the results of that is PMS.

Right.

Yes.

A damning indictment of the medical industry and modern culture as well, all in all in one go there.

there.

So, categorize for me these multiple phases across the month.

What's it like to be the female brain going through this?

What's happening inside of the female brain?

Yeah, well, so during the first half of the cycle, which you know starts on day one, which is the day that you get your period.

And at that point, hormones are pretty low and women are generally feeling a little bit wrung out because they just got through this big hormonal shift in the luteal phase.

And during the first couple of days of the cycle, women tend to be relatively tired.

They're bleeding.

They don't feel their best.

But usually after a couple of days,

because estrogen starts to rise, egg follicles are being stimulated.

And as they get stimulated, estrogen gets released and it makes women feel amazing, right?

They generally have more energy.

They have higher sexual desire.

They have more sex.

They're more drawn to men.

You know, there's just a whole lot of fun things that go on during that point in the cycle.

And it's just orienting women to do the thing that their brains and bodies need to do in order to reproduce at that point.

and that is have sex, right?

Because that's going to get an egg in proximity with some sperm, and then voila, you know, magic can happen.

After ovulation occurs, and that usually happens about two weeks in, so right around day 14 is when we see ovulation happen, that empty egg follicle actually becomes a temporary endocrine structure, and it's called the corpus luteum.

And it releases women's other sex hormone, progesterone.

And progesterone, like the experience of being in the state of this hormone, is one where we tend to be more emotionally sensitive.

So it actually changes the connections with the amygdala in the brain, which is our fear center, and it makes it more interconnected with a greater variety of areas of our brain.

And it makes it more sensitive to threat.

And so what we find in research is that during the luteal phase of the cycle, so again, these last two weeks of the cycle, that it actually lowers the threshold that women's brains need to consider something a threat.

You know, sort of like a smoke detector, right?

Like you can have a really sensitive smoke detector where every time that you so much as like make a pizza, it goes off and goes crazy, or you can have one that's really insensitive, right?

Where your whole house would have to be on fire before it goes off.

And what the luteal phase does is it kind of makes you have a more finely tuned smoke detector.

And again, this is a period in the cycle when women are incredibly vulnerable, right?

Progesterone is the hormone of pregnancy, right?

And this is true whether or not we ever want to get pregnant or whether our sex life would even allow us to get pregnant at a given point in our lives right but our body's preparing for that and part of that is that it does lower the threshold on what is considered threatening right so women do become sort of more socially astute to signs of potential threat You also tend to be sleepier and less motivated to go out and do things.

And again, this is part of the fact that

progesterone is ushering in this state that is optimized for pregnancy.

And this is a time that's really vulnerable for women.

And especially, throughout most of our evolutionary history, we were very much dependent on our male partners for provisioning.

If we were living out in the wild wilderness and we were being chased by

a mountain lion, it'd be more difficult to get away.

And so we tend to be more sort of oriented toward being home bodies.

So you actually find that women's motivation to like do outward-facing approach type motivation where you like want to go out and do things and the idea of pursuing goals feels really good that area those neurotransmitters get tapped the brakes get tapped on them a little bit to make women a little bit more introspective wanting to stay home wanting to stay safe again having a heightened tendency to understand danger signals in the environment you also get hungrier and sleepier because progesterone actually intentionally

causes the brain to have an increase in what's called GABAergic activity.

So it's just like activating the calming centers of our, it's this calming form of neurotransmission that slows the brain down and chills it out.

And it makes you, again, it sort of keeps you at home, right?

It's a very sort of relaxing type of a hormonal state.

It makes it so you don't go out and expend a bunch of energy unnecessarily.

And throughout most of our evolutionary history, you know, there wasn't a fast food place on every corner and it was really difficult to get calories.

And so maintaining sufficient calorie stores for pregnancy was a very important thing for the female body to do.

So, you're sleepier, you're hungrier, your basal metabolic rate increases.

So, a lot of times, women report feeling hungrier during the second half of the cycle, and that they're having these food cravings.

And it turns out that we're hungrier and have food cravings because we're probably not eating enough.

Because, even though we've all been given sort of like one size-fits-all nutritional guidelines about, like, you know, hey, Sarah, you with your activity level and, you know, your height, you should have about 2,000 calories a day.

And so if I'm a woman and I believe this to be true of every day of my cycle, I'm going to end up feeling kind of miserable in the second half because research finds that basal metabolic rate increases by anywhere between 8 and 11%.

So like if you need 2,000 calories a day during the follicular phase or during the first two weeks of the cycle, you can need an extra almost like 150 calories, close to 200 calories a day in the second half of the cycle and of course women aren't told this right and instead they're just like why am i so hungry and why am i having why am i craving food even though i already ate um and so that changes we shift from a pro-inflammatory type of an immune response to an anti-inflammatory type of immune response and that changes the way that our bodies respond to everything ranging from medication that we might be taking for chronic condition or even the symptoms that we have from chronic condition.

So there's a lot of research research showing that

women frequently experience premenstrual, they call it pre-menstrual worsening of symptoms like asthma and different types of autoimmune disease.

Many women report that their ADHD medication stops working

at this time in the cycle as well.

And it appears from the research that the way that we even metabolize drugs is different during this phase in the cycle.

And so, there's all these changes that go on.

And because we're not told about them and we don't know what we're supposed to be looking out for, and we're not told things, for example, like, oh, you know, you need to eat more.

Your calorie needs actually change as your body temperature increases.

A lot of times women walk around feeling pretty miserable.

And a lot of that misery is kind of unnecessary.

Because if we actually knew what was going on and what we needed to do to optimize and feel our best, I think that for a lot of women, PMS wouldn't be a thing.

So that's, I guess, what's happening inside of of the brain and body.

Can you just dig into the adaptive reasons for that on both sides?

Especially, I mean, you know, the obvious question here is, how is PMS adaptive if it makes women so miserable?

Across the entire cycle,

why are women predisposed to behave and feel all of the different ways that they do?

Right.

And again, it's, you know, it's because reproduction for us requires two different jobs.

I mean, when you consider the fact that our body has to, in the course of, and let's just assume a 28-day menstrual cycle.

Across the course of a 28-day cycle, a woman's body has to completely shift gears from first being optimized for attraction and sex, right?

And so that's what estrogen does, is it like pulls out all the stops to make us our sexiest, most energetic version of ourselves.

And, you know, sort of at the top of our game of being able to tell the difference between, you know, a really high-quality mate and like a slightly less higher-quality mate.

What's some of the research that you've looked at around this that sort of proves that this is to be the case?

There's some really great research that finds that women's ability to pick up on the different thresholds of a testosterone metabolite actually differs across the cycle.

And that when estrogen is high and fertility is high and conception is possible, women can actually distinguish between very fine-tuned differences in levels of testosterone based on scent-based cues of this metabolite that it releases when it's broken down in the body.

At other points in the cycle, women aren't able to tell those differences, right?

It's kind of like the difference between like you're drinking wine with somebody who's like a really, you know, like a wine connoisseur, right?

They can tell the difference between a...

you know, 2020 and a 2021 Cabernet, right?

Whereas somebody who doesn't have a lot of experience with wine, you know, might not be able to tell the difference at all.

It all kind of tastes the same.

The same is true for women in the estrogenic versus progestogenic phase of the cycle.

When you're in the estrogenic phase of the cycle, it's like women can tell clear differences between very fine-tuned differences in testosterone levels based on scent and also based on physical appearance of facial features.

So they've done some research.

This was actually some research that was done by one of my honor students, where we looked at women's ability.

We just like morphed faces by little tiny minute differences.

And then we asked women, tell us when you start to notice that these faces are changing.

And what we find is that near high fertility, when estrogen is high, women, it lowers their threshold for where they're able to see the differences, right?

It's like they're more attuned to the fine-tuned differences in testosterone levels in male faces.

And you don't see this going on in the second half of the cycle because being able, you know, keeping all of that cognitive architecture sharp is really metabolically expensive.

And what we tend to see in the cycle, I mean, just at the level of the brain, is that at high fertility, when you have high levels of estrogen, that it causes our neurons to sprout new dendritic spines and actually makes our brain more sensitive to the environment, right?

And it's because our brain, you know, it's in our eyeballs and our noses.

I mean, that's like the communication pathway between our brain and the rest of the world, right?

And so our brain becomes very sharp.

on the ability to be able to distinguish these fine-tuned differences in the quality of partners when estrogen is high because this is the time in the cycle when sex can lead to conception.

Then during the later phases in the cycle, it's like having that ability is a waste because sex can no longer lead to conception in the second half of the cycle.

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Why would distinguishing levels of testosterone through smell or through face be something useful or important at all?

Yeah, well, it's important because it's a hypothesized good genes marker, right?

And so the idea here is that testosterone provides a proxy cue to a man's genetic quality.

And usually when people are making this argument and the evidence that's been proposed in support of this general idea

has to do specifically with

immunological quality.

And the idea is this.

We know that testosterone is immunosuppressive, right?

It actually tamps the breaks down on the immune system.

And the reason for this is because testosterone like shifts the body toward all things sex and mating, right?

And that takes energy away from being able to fuel your immune response.

And so if a person has a lot of testosterone markers, it indicates the fact that their immune system is well enough put together that their body allowed high levels of testosterone to be released during development, leading to the masculinization of these features, like masculinized facial features, masculinized vocal cords, and so on, a masculinized brain,

that, you know, that their bodies were in sufficiently good shape that they were allowed to release this high level of testosterone, despite the fact that they were also having to manage, you know, whatever types of pathogens and parasites were in their environment.

So interesting.

So, testosterone is not necessarily the marker that women are looking for itself.

Testosterone is an indication that the physiology of this particular man is sufficiently robust that he has surplus immune system capacity, so much so that his body could suppress some of it with this additional testosterone, and he would still survive and still not be sick.

Therefore, high T equals good immune system, not necessarily high T is what we're after directly.

Right, exactly.

Yeah, no, I think that is both things, honestly.

But yeah, so you hit the nail on the head.

And then obviously there's some other benefits from high T directly.

I mean, just in terms of somebody being able to be a good protector and a good, you know, provider of resources, because we know that those things are correlated.

But in terms of the developmental markers, I mean, it's like whether somebody has a masculinized face or a masculinized voice or a masculinized build or a masculinized personality.

I mean, all of that's, you know, determined during childhood.

And so that's a story of their immune system being able to withstand, you know, reliably being able to withstand all of these threats while also releasing high levels of testosterone, leading to this masculinized phenotype.

Right.

Okay.

And then

so the argument here is women are more discerning of these sorts of traits.

They're able to see with kind of a higher resolution

during the first two weeks.

They are being more gregarious, being more outgoing, be more sort of socially

adept, I would guess, and more out there.

Wasn't there a study about strippers make more money during the first two weeks of their cycle as well?

Yeah, no.

So yes, there's this really great study that was done where they had women keeping diaries and they would just like indicate, did you get your period today?

Yes or no um they you know obviously put down how much time they spent at work and then how much money they earned and what they found was that even after you control for the number of hours they worked and so on and so forth what you found was that those strippers who were naturally cycling so meaning that they were not on birth control and they were able to enjoy uh the nice estrogen rise that you get prior to ovulation that those women earned significantly more money at high fertility in the cycle when estrogen was high relative to what they earned at other points in the cycle when estrogen is low.

And they also earned more than women who are on the pill because women who are on the pill, of course, don't ovulate.

And so they never got that big earning bump peri-ovulatorily, right?

Or right before ovulation.

And so they were sort of missing out on that like free of cost hotness surge that women are able to get from estrogen.

Wow.

Okay.

So

what's

I want to dig into?

I want to know what's happening happening with the ovulatory shift hypothesis stuff.

Because

it seems like this is suggesting women would almost certainly have different partner choices across the month.

That if you're able to detect cues of testosterone during the first half, then you're able to discern.

And if you're unable to detect them in the second half, then that's definitely going to have some sort of an impact on you.

But it seems to me, looking at different things that come across my Twitter feed and my Substack feed, that every week there's some replication crisis around ovulatory shift two.

So, given that you've been me deep in this, where do you come to sort of sit?

I know this is kind of a spicy topic in the world of EP at the moment.

It's always a spicy topic.

And I mean, and I think one of the reasons that it's a spicy topic, honestly, is because

I think that any research that's done on things that are related to women specifically, I think get unduly scrutinized in a way that I don't really think is fair.

But that being said,

yeah, it is a spicy topic.

And there's definitely been some issues like with replication.

I mean, there's just no question about it.

Where

some researchers will find, for example, that near high fertility in the cycle, that women do exhibit a heightened preference for masculinized male faces, voices, and behaviors.

Other research findings using maybe different methods or you know different types of ways of assessing whether you're at high or low fertility,

finding that they don't find this effect or they find it for some traits, but not other traits.

And so I think when you look at

the totality of the evidence, I think for sure there's something there, right?

So like one thing that I can say for absolute certain that I know is true because it's just been replicated a zillion times is that yes, women have an increase in sexual motivation at this time, right?

So women feel sexier, they smell sexier,

you know, et cetera, cetera, et cetera.

And there's pretty robust evidence on that.

In terms of women's partner preferences, the best studies that I've ever seen looking at this topic, so looking at how women's hormones change across the cycle and looking at this within women longitudinally, find that there is a preference shift and that women do have a heightened preference for these cues related to testosterone.

And so to me, I think that, I mean, and some of the stuff, like, you know, whether it's also symmetry, that one's a little bit up in the air.

I'm not really sure about that one.

And in, but, but with the masculinization and testosterone, I feel confident that there's something there.

And like I said, there's, there's been, you know, there have been some failures to replicate, but oftentimes when I've seen those failures to replicate, the methods are a little bit of a mess.

And I think that this is definitely something that you have to look at longitudinally within individual women because trying to make comparisons between women, I mean, when you look at like levels of hormones, and I mean, this is something that frustrates women no matter where they are, like if they're trying to get pregnant or they think that they're going into menopause or whatever.

But when you look at the range of like what's normal for estrogen, it's almost like the difference between like, if I were to say what's normal for a range of earning is like between $30,000 a year and about a million and a half, you know, and you're like, well, so then you get a test result back and it says you're normal, right?

And it's like, well, what the fuck does that mean?

Plus

receptor sensitivity and your psychological profile's predisposition, which gets enhanced or tuned down based on where your home is.

Yeah,

I can totally see how that would be the case.

What you mentioned there, women have high libido,

feel more sexy, smell more sexy.

How's that been tested?

So that's really interesting.

That's been tested in a variety of different ways.

So they've done t-shirt studies.

And with the t-shirt studies, they, of course, have women wearing t-shirts that they wear at night that they sleep in, and they can't wear any scented soap and no perfume and no deodorant, right?

And then they have men smell the t-shirts.

And what research tends to find is that when men smell the t-shirt of women near high fertility, so when estrogen is high across the cycle, that they prefer the scent of women at that time relative to the exact same women and in the later phases of the cycle when conception is not possible.

They've also studied this looking at panty liners.

So in one particularly provocative study, they had women wearing panty liners across the cycle, right?

So they would wear this panty liner for a full day.

And what the researchers did is they actually put the panty liners and they had them in groups, right?

So they had one group that was a high fertility panty liner.

So these are panty liners worn by women right near ovulation when conception is possible.

And then they had another group, then they had another another group of panty liners that were the exact same women during the luteal phase and then they put them in a nebulizer and a nebulizer yeah no i'm not no and they did this in south america because i don't think that we could get away with this in the us you the ethics boards wouldn't be keen on that one yeah they'd be like i don't know like you want me to vaporize the smell of a woman's panty liner and get men to breathe it in so that you can work out right okay yeah they'd be like so let me understand where the panty liner is going yeah no that our ethics board would not like it.

But so they did this really wonderful, it was a wonderful study.

It was a wonderful study.

And they had these men come in and they didn't know what they were smelling.

And so they just like

sniffed this thing.

They nebulized this thing and breathed it in, not knowing what they smelled.

Yeah, so like breathing this scent in, and it's just probably going to surprise you to learn, but men preferred the scent.

They preferred the scent of the women's secretions at high fertility compared to low fertility.

fertility and the best part was in addition to just like the liking score it increased men's testosterone and cortisol to be exposed to that scent of high fertility and you know and it just really you know goes to show you that if there's like a little bit there's like a whiff of mating in the air right and and and and with you know estrogen and and ovulation i mean this is the time when a woman can get pregnant from sex you know and if you have men whose like bodies are able to just kind of pick up on that, they don't know what's going on.

They're just like, wow, there's just something about this woman, right?

And that's going to be something that's very inheritable.

Was, did that study replicate, or has it been done again, the one where they got silhouettes of women walking and showed them to men?

Yeah, no, that was a great study.

And, you know, I have not seen any replication attempt on that.

And if it's not already in the works, I'm sure that somebody is working on it because there seems to be a whole group of researchers who

seem to be building their careers on.

Yeah, yeah, and trying to like, and trying to say that women's hormones actually somehow magically don't matter and that and that they we just they're just an extra

that was a really cool study.

So for the people that that didn't hear, I think we maybe even spoke about this on our last episode.

Yeah.

There was a study done of women's silhouettes walking.

So they completely kind of gotten rid of any of the features of the women.

And they just asked men, well, which of these women do you find most attractive?

And even the way that they moved was the women that they chose were the ones who were highest in fertility.

It was that point in their cycle.

So, yeah, you know,

I find it fascinating.

I'm glad that I'm not in the industry, so to speak.

I get to be a sort of willing cheerleader on the sidelines.

And

my career is not at the mercy of the waxes and wanes of whether or not ovulatory shift is in vogue or out of vogue or cancelled or brought back in or whatever, resurrected.

But okay, so that's the first half.

To summarize, women are more outgoing.

They're more likely to have sex, sex drive.

They are more attractive to men.

So they're both more discerning of men and also found more attractive by men.

So that's an interesting one.

I also haven't seen anybody.

I haven't seen any evidence suggesting that men's interpretation of female ovulation stage doesn't replicate.

So, yeah,

there's criticism around: do women's hormones do anything to women?

But there's no criticism around do women's hormones do anything to men, which is actually

pretty funny when you think about it like that.

And then we get into the second half.

And all of this is you are able to get pregnant.

Now's the time.

Come on, get cracking, lady.

And then you pivot into the second half.

You have the follicle release, the egg follicle release, which does a thing and then

what i'm interested in is the behavior in that second half yeah how is that how is that adaptive how is it being

miserable and and being low energy and needing more calories like what is that um engendering what is that encouraging um in like an ultimate uh outcome uh way Yeah, no, it's implantation and pregnancy, you know, and so the first half is really about attraction, right?

So we talked about all those things: sex, attraction, attraction, sex.

And then the second half is about creating a space where an embryo can safely implant, right?

And is gearing your body up for the possibility of pregnancy.

And, you know, even the process of building and fortifying the endometrial layer, which is this, you know, layer inside the uterus, it's very unsexy, but it's a lot of tissue that gets built during the second half of the cycle where all of this tissue is differentiating.

And it's a really metabolically expensive time, right?

So, women's body temperature increases almost a full degree during the second half of the cycle compared to the first.

And the reason for this is because our body is like working very hard to get all of the pieces in place that are necessary for pregnancy to occur.

And so, you know, we see these shifts in hunger, right?

Where we become hungrier, we become less outward-facing, right?

Like, we don't feel like going out and like going out dancing all night with our friends and, you know, know, going out and seeing a bunch of people because all of that is very energy expenditure.

It's energy expenditure.

Energy.

Yeah.

Like that's not a word, but it's, it expends a lot of energy.

And so it's like our bodies go into an energy conservation mode.

Right.

So we tend to want to eat more.

We want to sleep more.

We don't have as much energy for things because our body is using a lot of fuel to create all of this new tissue and differentiate this tissue to prepare for the possibility of pregnancy.

We're also, again, like we're

more cautious during this time because our threshold for what is considered threatening and not threatening changes, right?

As you said, it's almost like the resolution increases.

And this is why, you know, at one, you know, you could have something happen during the first two weeks of your cycle and it kind of rolls off your back.

So let's say your partner is like staying late at work a couple of nights a week that week and you're like, oh, okay, all right, that means I'll, you know, hang out and watch Netflix, the show I like that he doesn't like or whatever.

But, you know, two weeks later, that can make, it can sound your alarm bells, right?

Because what we consider, what our brain is willing to entertain or what the alarm bells are kind of tuned to, the amount of information that's needed to cue it as a threat decreases.

And it's because our brain is in the safety, you know, mode during the second half of the cycle in a way that it's not during the first half of the cycle.

And so we also get greater social sensitivity to threat.

And this is true both like with external threats, but also relationship threats.

And again, you know, when we think about the things that are important for women, and especially historically, in order to promote a successful pregnancy, it is having your village, right?

It's having a partner who's investing in you, because throughout most of history, single moms didn't do very well,

right?

And it's also having a community around you that's investing in you, because people without a community didn't do very well in terms of survival outcomes of themselves and their offspring either.

And so women become very dialed into those things and get really dialed into threats.

So that way they can be able to remediate, you know, and

it's an interesting contrast with being more extroverted, outgoing, party mode in the first two weeks with still being pro-social, but it's more sort of allo-parent-y.

It's what's my place within the sort of female hierarchy, hidden.

Who's leaving me behind?

Who's not leaving me behind?

It's kind of similar, but also superbly different.

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And women oftentimes feel more of a desire to stay sort of withdrawn, a little bit socially withdrawn, right?

So their relationships are important, but they don't want to be going out and hanging out with their friends, right?

And like spending a bunch of time doing outward-facing activities.

It is sort of more of an internal time where we're in an energy conservation mode.

And what's really funny is that, you know, this isn't something that is just specific to humans because even there's been research done on baboons.

And they find that female baboons, when they're in like after ovulation and they're in the sort of baboon equivalent of the luteal phase, rather than being on the ground and grooming one another, they sit up in a tree.

And like, I identify with that baboon sitting in the tree during the second half of the cycle.

Like, yeah, I just don't want to hang out.

I just like need, I just need a moment, you know?

And it's really interesting because even sex and the nature of the sex that we have tends to shift in the across the cycle.

How so?

And so, well, so, you know, it's really interesting because humans are kind of cool because most species, like a mammal, females don't have sex across the cycle.

They just have sex in estrus, right?

So during this time when sex can lead to conception.

And when you look at most mammals, that's the only time that they have sex.

And the reason for this is that sex is costly.

I mean, it's metabolically costly just from the act of it all, but it's also physiologically costly in terms of the fact that you're going to have an immunological event that occurs in your vagina because there's going to be genetic material that enters there that does not belong to you, right?

So this creates inflammatory activity, which is immunologically, i mean it's physiologically costly and it also can create um you know unnecessary inflammation which can be not the best thing to experience when you're getting ready for the possibility of implantation of an embryo right so all of these things make sex pretty costly during the luteal phase but nonetheless human women have have sex during the luteal phase.

So even though we see that sexual desire decreases and women do tend to have sex less frequently in the second half of the cycle than they do in the first half of the cycle.

When women do have sex, it's more often motivated by the desire to connect with their partner and sort of pair bond than it is from just like, you know, need to have it right now, sexual desire.

And so they've done some really interesting studies where they've looked at sex as a form, as sort of a mechanism of pair bonding in, you know, in humans and in other species like prairie bulls also have sex across the cycle.

And so they're oftentimes oftentimes studied to better understand like what is the function of a non-conceptive sex that's had in the luteal phase.

And what they tend to find is that it activates all these great brain regions that are related to pair bonding.

right so oxytocin and you know and it helps to um uh seal the bond which again you know for women who are in a state when they could potentially become or could be pregnant this is something that you need to do is like really work on the relationship um and help to ensure that you're going to have a good relationship with your partner, who throughout most of our history, we would have been very much dependent on during a state of pregnancy.

Because you know, women, as hunter-gatherers, when they're very pregnant, are not usually able to get enough calories to be able to feed themselves.

So, they're very reliant on men.

It helps to facilitate pair bonding.

They've done cool studies in humans, just even looking at

how women's sexual motivation changes across the cycle.

And what they find is that for women who are feeling the greatest need to connect with their partner, so women who feel sort of

relationally insecure with their partner and report that they care for their partner more than they feel like their partner cares for them.

So people who have the biggest gap in what we can think of as like, you know, perceived care for one another in the relationship, it's women who have the biggest gap between how much they feel like they care for their partner and how much they feel like their partner cares for them, who have the most sex and are most motivated for sex and have the highest sexual desire in the luteal phase, suggesting that it, you know, serves this totally other.

type of a purpose in the second half of the cycle.

And what's interesting about that, I mean, there's a lot of things that are kind of interesting about this, but one of the things I think that this is really useful for, especially, I mean, well, one, it's useful for women to know about themselves because I think a lot of times, you know, our beliefs about like sex, sex drive and sexual desire and sex and sex and sex is all very much based on sort of a male understanding of sexuality, which is just that we should be 100%,

you know, super turn-onable all of the time and that any failure to experience that is like there's something wrong with us.

And that's just not how female sexuality works.

And that it is cyclical and that you do see these big peaks and valleys with it tending to peak near high fertility and it tending to valley during the mid-luteal phase, so about three weeks into your cycle.

But it's also really good for communication, you know, and being able to understand in yourself that luteal phase sex is probably different.

Being able to explain to your partner, like, yeah, you know, last week, a really hot quickie right before my afternoon meeting is exactly what I needed.

That would hit me the wrong way right now, right?

Because right now, sex is about connection.

It's not about just, you know, like, let's have sex and then get out of here because that's not going to feel right.

And understanding these things and being able to communicate these things, especially to women who have male partners,

super helpful.

And it really can make the relationship a lot better because women are better able to articulate their needs to their partner.

And then, of course, their partner is better able to meet their needs.

It does make sense.

You know, the concealed ovulation thing for women, why is it that we have sex outside of the time when you can conceive babies?

Well, it's that human babies are really effortful to raise, which means that you need to have both partners very heavily invested.

Male parental investment is relatively rare, even in great apes, let alone in mammals across the board.

Most dads are deadbeat dads.

In fact, human, even the most deadbeat human dad was probably more present than almost every other mammal dad.

And okay, so we need the bonding.

That's why you got to, it's kind of hard to have sex.

That's potentially why ovulation is concealed.

Also, maybe so that your female intrasexual rivals can't fuck with you and mess with your like release of eggs.

And there's a bunch of different reasons, right?

But

as soon as you accept the fact that sex is not just for procreation in humans, then this, you don't even need really the studies to be able to tell you that this would be the case.

You could just induce it from that fact.

Okay, sex is not just for procreation.

Okay, so at least sex is for two things, right?

It's for the procreation, because if it wasn't for that, you wouldn't get any future generations.

And it's for the pair bonding.

So all that you're saying here is, here are the building blocks of how that looks, what that looks like.

This is where and when this tends to happen overall.

Not that procreation sex isn't bonding and not that maybe you mistimed your cycle and like an egg did get released and like, oh, we got pregnant in week three or whatever.

Right.

Yeah, no, absolutely.

And it's just more about like unconsciously, like what are the processes that's guiding the behavior, which I think can be really helpful.

So just to, you know, give an example of this, you know, if we know that sort of ultimately, right?

And so we're just talking about like ultimate, the ultimate evolutionary reason that women have sex outside of high fertility is that it's promoting this pair bonding function, right?

And it is increasing connection.

That's probably not a really great time if you're a woman who wants to just have casual sex, to just like have casual sex, right?

Like, if you're going to be having casual sex, and they obviously don't want to have a lot of casual sex when you're ovulating, if you're not using some form of birth control, but like, if that's true, it might impact the timing of your decisions because I'm willing to bet, I have not seen this study, so that's my caveat right there, but I would be willing to place a bet on the fact that it is more difficult for women to avoid emotional entanglements of sex as had specifically in the luteal phase compared to outside of it.

Just because of that

pair bonding.

If you have a one-night stand in the second two weeks of your cycle, your brain is going to be tricked into thinking this is someone that you should be bonded with more closely.

So the sleep with him and not catch feels may be able to work.

I think that's still pretty up for debate as well.

But if it can work, it may be more likely to be able to work during the first two weeks than in the second two weeks.

Yeah, that would be my guess.

And again, it's like you're saying, it's not like the sex that we have in the first two weeks of the cycle isn't also about connecting.

It is, right?

And what our proximate level motivations are aren't always necessarily in step with the ultimate reason why we inherited a trait in the first place.

But nonetheless, you know, given that we know that, especially from the work in the prairie voles, that this non-conceptive sex is serving this like, you know, relationship cement function by releasing all these neurotransmitters that are related to pair bonding, it just seems to me like it would be a little bit more of a catching-feels, high-risk type and a time in the cycle.

I suppose one thing I was thinking as you were talking there was: what's the likelihood of extramarital, extra-partner sex occurring?

Maybe it would be the sort sort of good genes, whatever, protected provider type mate switching hypothesis thing.

But then I also think, how are you supposed to separate out just I have more sex drive in the first two weeks, therefore I was more likely to do the sex?

You would somehow have to be able to control for sex drive and adjust that across the cycle and then be like, okay, given same levels of libido, Are women more likely to sleep with another man that isn't their main partner?

It seems like a little bit of a difficult one to arrive at.

Yeah, I think that one would be difficult to arrive at.

I know that they've done the studies where they say that, you know, lo and behold, women are more likely to have sex with their affair partners at high fertility in the cycle.

But as you noted, you know, women are just more likely to have sex in general.

And so, you know, I don't know that anybody has found a really smart way to tease those two things apart.

So

it doesn't sound to me, yeah, there's, you know, you need more calories and you don't want to hang with your friends and go to brunch with the girlies and heels on or whatever.

And yeah, maybe you're a little bit more sensitive to your partner staying late at work or not giving you a cuddle before he wakes up in the morning.

But, you know, largely, this just feels like a sort of relatively gentle swing between two different types of womanhood.

And yet PMS reliably makes lots of women miserable.

So what's the disconnect here?

Is this just my male brain?

Am I unable to see it?

Or

is there more when you put this sort of suite of traits together that makes for a particular type of existence?

Well, so I think it's a combination of things.

So I think one of the reasons that it feels worse than it needs to is just simply because women haven't been given a blueprint for themselves that's anything other than just a smaller, you know, sort of pinker, you know, like less hairy version of a male way of being, right?

And so I think that like we've kind of downplayed the impact that our hormones have on creating different types of physical and psychological states.

And so I think that, you know, the things that we do aren't necessarily going to be optimizing ourselves during that time and that can make us feel worse.

And just to give the example again, you know, we need more calories.

If we're not eating those calories, we're going to have food cravings, we're going to be hungry and we're going to be cranky, right?

Another example is that, you know, our recovery needs change during the luteal phase.

And if you're just expecting that you're going to go and do like a really hard HIIT workout and then you're going to go for a run and then you're going to get, you know, X amount of sleep and you're going to feel great the next day.

That's not necessarily going to be as true in the second half of the cycle as it is in the first because your HRV gets lower because your heart rate increases, your body temperature is higher, your respiration is faster.

It's like, so it's harder for us to get, you know, calm down during that time.

And

so that, that too, it's like a lot of women are, you know, by doing like a one size, one cycle phase, like fits all like set of like workout activities or, you know, their, their self-care routine if all of that is treating themselves as the same version of themselves every day of the cycle it can make them feel pretty terrible in the second half of the cycle because it does require more care right it requires more food it requires more rest it's harder to work out you build less muscle from resistance training during that time because progesterone is catabolic and estrogen is anabolic and so is testosterone which tends to get co-released at the same time that estrogen does in the cycle and so it's like we have all of these changes and the fact that we aren't acknowledging them, right, culturally, it's just like, oh, hormones don't matter, you know, whatever, like men and women are the same.

Women are just small men.

So these don't matter.

And so I think part of the reason that we feel bad is because if we just made small adjustments in the way that we treat ourselves and understand what our body is trying to do, I think that we can feel a whole lot better.

And the other thing is that, you know, there's a lot of things just because of an evolutionary mismatch between the environments we spent most of our history and the ones that we live in now that can really erode at our ability to be able to sort of ride the wave of hormonal change in a smooth, comfortable way.

Because being able to, as a woman who cycles, be able to go through these wild hormonal swings that happen, especially in the luteal phase, because the rise and fall of progesterone peaks at levels that are 10 times higher than the peak levels of estrogen rising and falling in the first half of the cycle.

So So you have these huge hormonal swings, and being able to have all the cells in your body that pick up on sex hormones be able to adjust to those things in a sort of rapid fire way that allows you to kind of smoothly transition through the cycle.

Those things get eroded by things like bad diets, not enough sleep, not enough sunlight, you know, not getting exercise, all of these things that increase and cause inflammation in the body erode at our resilience to hormonal hormonal changes, and that also has the tendency of making these things feel a whole lot worse than what they need to.

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Is it right to say that women are more hormonal than men?

Like whose behavior is more hormonally mediated?

No, I mean, it's not.

You know, it's like our hormones are different, but we both have hormones and our hormones cycle, right?

So, for a man, you know, testosterone lives on a 24-hour cycle.

So, testosterone peaks in the morning hours and then it decreases over the course of the day.

And then, of course, testosterone, unlike women's two primary sex hormones, changes dynamically in response to things in the environment, right?

It's a reactive hormone.

So, if you see a beautiful woman or you smell a pantyliner that's somebody who's called into nebulizing by a South American researcher, Yes, it's a nebulizer.

Your testosterone will increase.

But men's testosterone levels, I mean, they change and, you know, and that affects men's behavior.

Women's sex hormones change in very predictable ways across the cycle, and that changes women's behavior.

And they're supposed to do these things.

You know, it's like women's bodies, we have two jobs to do to reproduce, sex.

pregnancy and so a cycle is just orienting our brain and our body toward those goals right and so for a man you just have have, you know, they have the primary sex hormone, testosterone, and it has that, you know, nice circadian rhythmicity where, again, it peaks in the morning and then is lower at night.

But then it also changes in response to anything in the environment that changes the benefits from sex.

You know, so if a man wins a competition, it's like, oh, yeah, no, I just won a competition.

So I'm at the top of the heap.

So now is a good time to go find a girl because, you know, women like winners.

And so this is a great time to mate.

Or you see a beautiful woman, like testosterone will go up.

Like, oh, yeah, I know, it's a good time to mate.

It's also the same if you were in a room with weapons and then it goes up even more if you pick the weapons up.

So

I've already kind of swallowed the uncomfortable, like real, maybe this is like the testosterone pill, which is that men's behavior is hormonally, maybe even less predictable than women's.

in that it responds to the environment in ways that you can't, at the start of the day, I don't know if I'm going to be in a room with a ton of axes, right?

I don't know if I'm going to get to wield one and pretend that I'm a mage for a small amount of time.

Whereas, at least, women have got this idea across a cycle.

I think I know where I'm going to end up.

At least in my experience,

it's easier to lay it at the feet of hormones because it is more predictable.

Like, why was that guy cranky that day?

Why was I cranky today?

Or why was I aggressive today?

Or why was I feeling a little bit passive today?

I don't know.

And, you know, if I would have to guess, though, that given women have got multiple hormones acting on them more so than men, that means that the swings in behavior, I would expect to mean, well, progesterone is not going to be impacting men in the same way as it does for women.

But I don't know, maybe testosterone is so powerful that it causes swings in behavior that are greater than simply estrogen, progesterone.

I'm not sure.

I just.

So I don't know.

So I'll say this, you know, it's like, like we have these, and as you noted, I mean, women's hormones, they change in this incredibly predictable way.

And the thing I always say is that if you tell me a woman's age and when she had her, the first day of her last period, I can tell you with a pretty decent degree of accuracy what's happening with her primary sex hormones.

Whereas with men, I couldn't do the same thing at all, you know, because I have no idea.

It's like, did you just see a beautiful woman?

Yeah, were you in a room with a bunch of axes?

Like, I have no idea.

And so you get a lot more volatility in male hormones, just meaning that they're less predictable than women's, right?

Just because our primary sex hormones change in a predictable way, men's primary sex hormone changes in a relatively unpredictable way.

But yes, we do have two primary sex hormones and men have one, right?

And so this does mean that we do that we cycle, you know, and it's because again, we've got two jobs our bodies need to do in order to reproduce instead of just one.

And, you know, and that's been used to argue that there's something wrong with us, right?

Like, oh, well, you know, women are just more hormonal and you don't know what you're going to get.

But, you know, the fact of the matter is, the only reason that we have that narrative is because men came first, you know, just in in terms of understanding what it means to be a human and it's like we could very quickly imagine a world where women's biology was understood first right then we would look at men and we'd say this is too simple like these guys like how can we know that he can make a good decision when he only has one hormone.

You know, he can't even look at something from two different angles because he's just got this one primary hormone.

I mean, it's the idea that we think that there's something wrong with our way of being is just an artifact of the fact that men were studied first.

And so that was like all of our assumptions about what it means to be normal and for things to be done right are based on a male standard.

It just doesn't work for women.

How many women understand what their cycle does to them, do you think?

Not enough.

You know, it's like we, I didn't, I didn't learn about any of this stuff until I was in graduate school, you know, and at that point, I mean, I guess I got my period when I was like 12 and a half.

And so I'd had it for a really long time and I had no idea what was going on, except that I knew that it was, you know, related to the ability to reproduce.

And I know that it meant that I had to buy tampons.

But other than that, I spent zero time thinking about it.

Most women aren't taught anything about any of this stuff.

And the result is that a lot of people are feeling either confused or

feeling bad.

Can we really expect men to understand it if most women don't?

I think, well, so I think two things.

I think one, I think that it's very possible for us to do a better job of educating women about what's going on with their bodies.

And, you know, part of the reason I wrote my first book was, you know, with the birth control pill was talking and providing that information because that's information women oftentimes aren't told.

And the reason I wrote the new book, The Period Brain, is the same thing.

It's just like trying to educate women about.

Here's your biology because no, you know, the public school system is not going to teach it to you.

So I think that we can do better in terms of educating women.

And in terms of educating men, I mean, I would hope that if you're a man, that you'd want to know this information.

And not only just in a like, oh you know i love women and you know want to be supportive of women i'm an ally i'm a menstrual ally yes i'm a menstrual ally you know what i mean like and it's like not just in that way but it's like as my husband says he's the most dangerous man in the western hemisphere because of all of the information that he has about the cycle um because he i mean it's like when you understand how women work it really does i mean and obviously you could use that to exploit women.

And that's not what I would like to recommend to anyone, but it really helps you be a better partner.

It helps you be a better friend.

It helps you be a better father.

I mean, just understanding how women's biology works.

I can't, you know, most men want to understand women.

And this is, this is the key right here.

It's like, understand our hormones, understand how those shape our reality.

And then I really think that it makes for better relationships.

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That literally happened yesterday.

That happened yesterday.

Yeah, no, yeah, no, I had heard about that.

I didn't hear why.

Like, I had heard that there was a breach.

I didn't hear the details.

So, that I'm sure that they were trying to, you know, they're pinning you with pink lace doilies and sucking cuddly toys when, oh, she's in her, she's in the second half of her period.

We need to get her with all of the fluffy stuff, like tea cozies.

She'll love that.

You mentioned the pill.

Talk to me about how the pill impacts the period brain, like tying together buck one and buck two.

Yeah, so the pill essentially takes, you know, we've been talking about the fact that women have our bodies have these two jobs we have to do to reproduce.

And the result of this is that we wax and wane between these two hormonal states, right?

The estrogenic state, which is like the wild sex kitten version of ourselves, and then, you know, progesterone and the luteal phase, which shifts us into kind of our earth mother, you know, mom genes side of ourselves.

And so for a naturally cycling woman, you're kind of waxing and waning between these these two, these two different but complementary states.

And when you take the birth control pill, it shuts all of that down.

So essentially, what it does is the progestin, which is the money maker, I mean, just in terms of the action that prevents pregnancy in different types of hormonal birth control, but that progestin is mimicking the acts of progesterone, which again is that hormone that's released during the second half of the cycle.

And it activates progesterone receptors in the brain.

And when the brain is reading, when the progesterone receptors are reading a signal, so they're getting signal, that tells the brain not to stimulate the ovaries to not produce an egg.

And then, of course, you don't produce estrogen.

And then if you don't ovulate, you don't produce progesterone.

And so

by virtue of these synthetic progestins, which are very different from progesterone, by the way.

So we don't need to get into the weeds on all of that, but just for listeners to understand that the way that you feel on a progestin, which most women feel pretty awful, is not the same as the way that you feel on progesterone.

They actually are completely different molecules and they act very differently in the brain and very differently in the body.

But the progestins do get picked up by the progesterone receptors in the brain sufficiently enough to, you know, inhibit the brain from telling the ovaries to release an egg.

And so, what this does is it flatlines women's hormone production.

So, women are no longer producing high levels of their own endogenous or internal sex hormones.

And instead, they're getting the same daily dose of a relatively high level of synthetic progesterone, known as the progestin, and then a relatively low level of estrogen.

And what this means, of course, is that when you're on the pill, you don't get that nice, big, beautiful bump in estrogen that makes women feel so sexy and alive.

And instead, you're living in this state of hormonal deja vu where you have a relatively high level of progestin and a low level of estrogen.

And this, of course, you know,

it it has all kinds of sweeping effects on the way that we think and feel and experience the world because our hormones, of course, play a really integral role in what that means for women.

So is it kind of like permanently being in the final two weeks?

It's kind of like being in the final two weeks, but with a caveat.

And so I'll just quickly, without getting into the weeds too much, just say that, you know, on the one hand, it's like the last two weeks of the cycle because you do see a decreased sexual desire, for example, and you do see less of a preference for masculinized male faces, voices, and behaviors, right?

And so you do tend to see some of those changes in sexual psychology that are similar to the second half of the cycle.

But you also get a bunch of other stuff that

nobody's really bargaining for when they're taking hormonal birth control.

And the reason for this is that the synthetic progesterone that is used in most commercially available birth control is not synthesized from progesterone.

And in fact, no progestins that are used on the market are synthesized from progesterone.

They're all either synthesized from

testosterone, most of them are synthesized from testosterone, or they're synthesized from spirolectolone, which is a diuretic.

And this is important.

This distinction between something, you know, this progestin, which is synthesized from not progesterone, right, either testosterone or spirolectolone, and progesterone ends up being really important because when the body is breaking down actual progesterone, it releases this really calming metabolite.

It's a neurosteroid called alloprognanolone that's really good at promoting mental health and mood stability and a bunch of other things that help women function and feel pretty good.

Whereas these progestins, when they're being broken down in the body because they are not made out of progesterone, you don't get the release of allopregnanolone.

And so women who are on the pill actually have really low levels of this really calming neurosteroid that does help to promote mood balance, mental health, and other things like that.

And it's actually been argued that, you know, this is probably one of the primary mechanisms by which hormonal birth control has been linked with mood disorders and anxiety disorders.

Contraceptives raise depression risk by 40% in teens and women.

Yes.

Yeah.

It's pretty, it's pretty, uh, pretty substantial.

It's a pretty substantial increase.

And it's something that, you know, until recently, and it's even now, it's like only the Europeans are actually stating this, like their, their, um,

their group that, you know,

does the licensing for OBGYNs finally, you know, acknowledged that yes, you can get mood-related side effects from hormonal birth control.

The American group is less to, um, less quick to accept that and like make that something that they communicate to their patients.

But yeah, it's a real issue for a lot of women, especially teenagers.

Teens are the ones who are asymmetrically hit with the mental health side effects from the pill.

And so it's likely the result of those funky progestins and the fact that they don't metabolize like a regular progesterone.

Interesting.

Okay.

Women.

on the pill show a 10 to 20 percent lower relationship satisfaction.

Where's that coming from?

Yeah, that's really interesting.

So

my guess is that what's happening with that is twofold is that one, anytime that you have some sort of a mental health related thing, like something like depression or anxiety that might be caused as a result of the lack of allopregnanolone of pill users, that can just decrease your satisfaction with everything.

Right.

So it might not necessarily just be about your partner.

It just might be that you're more critical about everything.

And so that's one possibility.

And another possibility is that I think that when you aren't able to experience yourself as a naturally cycling woman who's going between these phases, you know, of estrogen being high and then progesterone being high,

it's like when you're naturally cycling, you get the full bandwidth of like what's good in relationships, right?

Like you're able to like really, you know, feel sexual satisfaction and desire and you're able to feel, you know, this like emotional closeness and desire.

And I think that that is part of what creates within us, like the feeling that we have a satisfying relationship.

And for women on the pill, who generally have lower levels of sexual desire, right?

And they've also tend to report lower sexual satisfaction, less attraction in their relationships.

And not necessarily because they chose the wrong partner, right?

Although there's some research that indicates that that might be a risk too, but instead, because they're not experiencing sexual desire, it's just like turning the volume down on what is a really important aspect of a romantic relationship.

And so not to really have much of a libido and then not to really feel that much attraction to your partner just because, you know, attraction and sexual desire is all fueled by estrogen.

You know,

yeah, and it's suppressing that.

And so it's like women are missing out.

It's almost like you have a jigsaw puzzle and you take out like half of the pieces and then you're like, how do you like the puzzle?

You're like, I don't know.

I guess it's okay.

Is it right to say women on the pill lose an authentic part of themselves?

Yeah, I do.

I do.

I think that is masking an authentic part of yourself, you know, and this could be for better or for worse, right?

The same way that we could say, you know, that taking an SSRI or an antidepressant is masking, you know, a person, like a real essence of a person as well, which I think is true.

But, you know, some people prefer the way that they feel on it.

And so they want that to be masked, but it is nonetheless masked, right?

And the same with the birth control pill.

It's like it's not, you know, you're not really yourself when you're on the pill.

And like I said, and that could be for better or for worse.

Some women feel better when they're on it.

And they like that version of themselves.

And, you know, and if that's, if that's how they feel, Godspeed, you know, you can be on it safely and it is and it's effective.

So

could oral contraceptives be the biggest unexamined mental health experiment that's ever happened?

Yeah, no, I think so.

I do.

I think that and teenage antidepressant use, I think that both of those things are.

And a lot of those are going to be happening in collaboration with each other as well.

Yeah, no, they are because the risk of being prescribed and antidepressant goes up significantly after you start hormonal birth control.

Oh, man.

Well, look, I remember the first conversation that we had.

When you came out, it was at episode 550.

Remembering that episode 1000 comes out next month, right?

Oh, my gosh.

I know.

I was early to the Dr.

Sarah Hill party.

I love it.

A bunch of things have sort of come to mind as you've been talking.

First one,

you mentioned, we've both spoken about how men's hormone levels are environmentally mediated.

So local ecology, wherever you are that day, what's going on?

Did you just win the lottery?

Did you win the sports game?

Did you get to touch an axe?

Was there a hot girl?

Like, how big were a boobs?

That big?

Or bigger?

Wow.

Like, more testosterone.

And

one of the things that we came up with, which I've still never heard anybody actually put forward as a theory, but I still talk about this all the time.

There is an X factor that appears to be missing missing from the decline in men's testosterone: that it's the microplastics, it's the fatness and obesity, it's the lack of sunlight, it's the

all the way down.

And still, a lot of testosterone researchers are going, this can't be the whole picture.

What we said last time was,

well, given that men's testosterone levels are mediated by the fertility of the women around them, if men who smell panties during the fertile phase get more testosterone than men who smell the panties from the second half phase, that means that if you chronically, globally suppress female fertility signaling, whether it's through smell or touch or the way that they walk down the street or the size of their boobs or how much makeup they put on or how outgoing they are, whether they come up and talk to you in the bar, all of these things, right?

This big sweet.

Um,

there is absolutely it is, I would put all of my money on the line that it is a non-zero effect on men's testosterone.

So not only

is birth control impacting female hormone levels, but it is 100% impacting male hormone levels as well.

Yeah, no, I totally think so.

I think so.

And actually in two ways.

So it's so funny that you say that because I talk about this all the time too.

And no, and there's still no research on it.

And I talk about it.

I talk about it constantly.

It's our secret little

bit.

I was going to say, yeah, no,

I think that we need to like, we just need to put this to bed bed and we need to have a study we need to do the we need to do the research and and get it done so we can um we can work on collaborating on a project on this i'm like fascinated by this so and here's another piece of that right so one piece being that um and this was something that just occurred to me last year so i don't think that this made it into our last our last conversation but with the um as you were noting it's like yes we know that men are sensitive to fertility cues right and and that men's testosterone responds to fertility cues and so there is like almost no way Like, I can't imagine a universe in which men's testosterone levels are not being impacted by the fact that so many women are on the pill, right?

Because you have all this

suppressed fertility.

Of course,

men's hormones are going to respond to that.

And of course, that has to be contributing to the decrease in testosterone that we see in men.

Another piece of it is, and I think this is interesting, and it's also related to birth control, but indirectly.

And that is, you know, there's this really great research that has been done now for a couple of decades now,

looking at male parental investment and testosterone levels.

Are you familiar with this work?

Oh, no, teach me.

Oh, teach me.

Okay, so are you ready?

You ready for the depressing facts?

So it's actually not.

No, it's actually brilliant.

Like, this is like brilliant design of the human.

This is how brilliant our bodies are.

So when men have, like, get into long-term relationships, for example, their testosterone goes down a little bit, right?

And it does this because it's obviously very adaptive to stop paying attention to the next door neighbor every time she's out watering the lawn, right?

If you're trying to maintain your pair bond, right?

And so you get this little bit of break tapping that goes on with testosterone levels.

Well, when men have children, break gets tapped a little bit more, right?

And again, it's counterproductive if you're a man who's trying to, you know, who's in a long-term parabond that you care about and you have children that you care about, it's counterproductive to have all of your energy focused on looking at beautiful women, right?

You should instead, you know, have your energy focus elsewhere.

There's also research showing that the more time you spend caregiving, the more the break gets tapped.

Okay.

So your break just keeps getting tapped.

And so they've done these really great longitudinal studies on fathers, and they find that, you know, over time, men who become fathers, like you get this decrease in testosterone that corresponds with fatherhood.

It's the greatest for men who do the greatest amount of caregiving.

And so one of the things that the birth control pill has done is allowed women to enter the workforce en masse, right?

So women are into the workforce en masse, working, working, working.

What are women doing if they have children with their partners?

Are they saying, well, I'm also going to do all of the mothering?

No, right?

Instead, we've become more egalitarian with parenting.

And now, even though women still do the majority of child care, and even though, you know, men have kind of come a long way in terms of being willing to chip in, women are still shouldering most of it, but men are doing more than they used to.

And with greater male child care, tap, tap, tap goes testosterone.

And so I think that god damn it, ladies.

Come on,

we just want to be able to gain some muscle, leave us to it, stop making us get into relationships and stop fucking tamping your fertility down and work walking in unsexy ways and making us hold babies.

Yeah, it's terrible, yeah.

We're we're a really, we're a terrible group.

Well, what it shows, what it what it shows is kind of how um

global this impact is, uh, how sort of macro and it's lots of different things happening all at the same time.

I guess

something else, which is kind of an implication here, is that

in the past,

the

waxes and wanes of how hard women worked and how much they did ancestrally, that must have tracked more closely with, or at least this is what I'm reading as your implication: that women don't understand that they need to kind of have a different lifestyle set up in the final two weeks versus the first two weeks.

But by building a

work environment, nine to five, five days a week, four weeks per month, that that

doesn't exactly allow for the flexibility.

And we need to show, like the meeting is happening next Thursday, whether you're on your period or not, whether you're fertile or not, like these things are happening because, again, men's changes in hormones

don't occur with the same sort of regular swings in that kind of a way.

And because maybe in that way, you could argue they're more predictable or at least, sorry, less subject to change like like across a month uh but less predictable within a day something like that might be an interesting way to put it um

i the

i guess the rough question here is does this mean that the high-powered super women boss bitch career ladies who are chasing down something that they really want to do are they going to be subject to burnout more quickly because they are pushing themselves and putting themselves into a world that they weren't designed for in that kind of a way.

They're not designed for this

like 28, 28, always on

workflow style in the same way that a man with his testosterone level might be.

Right, right.

And I mean, there is a lot of research evidence that suggests that women are suffering from burnout at a greater rate than men.

And I do think that that is part of the picture, right?

Is that

it's easier easier physiologically for us to get burned out than it is for men just simply because we do have those cycling hormones.

Now, the good news is for women, you know, it's like you do at some point go into menopause, right?

And then at that point, it's a finish line, ladies, it just happens to be menopause.

Yeah, no, and well, no, and

you know, and these things don't need to be like, it doesn't need to be the sort of thing, like when we're experiencing these changes across the cycle, it doesn't need to be the sort of thing where you're like having to have, you know, ask your boss to like schedule your meetings around your period or whatever, because I mean, that's like bullshit and totally, you know, not the way that the world works.

And it's not even necessary.

I mean, instead, it's just about making sure that you're taking care of yourself, you know, and especially during the second two weeks of the cycle.

I mean, it's, it is easy to get burned out during that time.

I mean, it's your, your heart rate is up, your HRV is low, you're, um, it's harder to get into deep sleep.

I mean, there's all of these things.

Don't more women leave their jobs?

They resign from their jobs during the second half of their cycle.

Is that it?

I have not seen that.

But let me, like, I would speculate that if that is true, that again, it's because we, I think that we become a little bit more exacting about

our boundaries at that time because of our sensitivity to social-related threats at that time.

But no, I've never heard that before.

That's an interesting one.

But no, I think

this

injection of women into the workforce,

think about it this way.

You know, you mentioned the menopause thing there.

There can be a world if a woman wants to be sexually active, but not have kids from the age of whatever, 14, 15, 16, if she goes on hormonal birth control, she can have this sort of flattened

wave.

hormonally, a reduction of her authentic self of being able to use the,

yes, changeable, but also pretty insightful opportunities that those changes in hormones all the way up until, oh, menopause happened.

Brilliant.

Like at no point in your life, really, as an adult woman, did you get to touch the sort of full breadth of experience that is available to you through this, just as you then came into land and now all the hormones have stopped.

Yeah, no, and you know what?

I mean, honestly, you see that with some women and that's the way they like it.

You know, so I know women who have been on birth control forever.

They have no children, right?

And they're getting ready to go into menopause, they're just stay on birth control until they're in their 50s and know that they're never going to have to worry about a cycle again.

And the reason for that is they like the predictability of it,

and so I guess it's kind of cool to be alive at a time when that's an option, right?

Because I mean,

yeah, right.

I mean, it's like if that's what you want to do, then like I said, godspeed.

And we know that you can do it safely as long as you don't, you know, sort of have all these other different types of contraindications.

And so, if that's kind of the way that you want to go, then then you know, you can.

In that way, would being on birth control make

I was gonna, I was gonna try and say something along the lines of birth control is kind of like a performance-enhancing drug for women that want to be in the workforce 28 days a month.

That it is reducing the wanes, but the problem is it's not necessarily just reducing, it's just shifting you permanently into the second one.

Um, so yeah, maybe you're more predictable across the month, but it's not allowing you to have that, you know, hard charging gusto that you might do during the first two weeks.

So,

it's not actually a performance enhancer in that regard, I don't guess.

Yeah, yeah, yeah.

Well, it's well, it's interesting because you also, I mean, in addition to the things that we talked about with estrogen, just in terms of making you sexy and you smell good and you walk sexy and the whole thing, is it also it acts like miracle grow in the brain.

And we kind of talked about this with sensory thresholds and being able to sniff out a good mate.

But you also get it in other areas of the brain that are related to learning and memory.

And so one one could argue that you're also then, if you're just flatlining your hormones with pill, that you also then lose out on the nice benefits to learning and memory that you can get near high fertility as estrogen

causes the sprouting of these beautiful dendritic spines in our neurons.

There's a big denial of sex differences happening at the moment in many versions.

But certainly one of them is coming from women, specifically, typically women on the left, that women are just the same as men, but somehow better.

Like they're the same as men, but just better in some ways, too.

Is this a self-defeating approach, given what you're looking at now?

100%.

I mean, look, we've all been led to believe anybody who believes that, you know, women should be in the workforce and, you know, and all of this sort of thing, which I 100% do.

I obviously am in the workforce.

I've been a scientist for the last 20 years.

So, you know, I obviously am a champion of women being able to hold down positions of authority.

But we've all been led to believe that sort of the path to our freedom, right, from the quote-unquote patriarchy, which is its own thing, because the patriarchy, a lot of times, is women.

It's other women.

It's not being enforced by men.

It's logical.

Yeah, no, yeah, no, it's usually enforced by other women.

So

that's a different podcast for a different day is about the patriarchy.

But, you know, we've all been led to believe that the path to liberation is to deny that biological sex matters and that, you know, that hormones don't matter and that biological sex doesn't matter and that we're just the same.

But the fact is, when we deny that we're the same, then, you know, we have a bunch of medical research that has been tested on men and misapplied to women, which has led to, you know, eight out of 10 prescription drugs are pulled from the market during the first year of use because of unanticipated side effects in women, because we're not being tested enough.

When researchers actually include women as subjects in research in only about 20% of studies, this was a neuroscience review that was just done.

When they include both men and women, only about 20% of the studies actually study them separately.

They actually test for sex differences.

The rest just lump males and females together and just assume that they're going to be the same and they're not.

And of course, you know, and we know this because like when you look at the risk of like depression, for example, you know, the rates of depression are twice in women what it is in men.

And then things like, you know, autism spectrum disorder is like twice in men what it is in women.

And the idea idea that we can be studying things like depression and

autism spectrum disorder in men and women together and not even looking for sex differences is completely absurd.

And so, no, I mean, it's not the path to enlightenment.

And instead, it just really puts women at risk of everything ranging from, you know, side effects from medication to, you know, we just learned that seat belts were designed with a male in mind and they don't protect female bodies the same way that they protect male bodies.

And so now there's a cry to put, you know,

seat belts in place that are good, are equally as good at protecting a female body as a male body.

We get the reasonable

seat belts.

That's what's going to be needed.

No, but like, I mean,

even like the reasonable person standard in law, and I'm sure that David Buss has talked with you about this, or you've had conversations with him.

But, you know, in the world of the law, there's this reasonable person standard for things like, for example, sexual assault or sexual harassment, and sexual harassment in particular.

And the idea is, would a reasonable person find this act harassing?

Right.

But the reasonable person that's used in the mind of the law is a reasonable man.

And women and men see things differently when

it comes to whether or not something constitutes sexual harassment.

So it's like all of these, you know, things where we just like try to pretend that biological sex doesn't matter.

It usually ends up coming and biting women in the ass.

And so I think that the thing that we need to do is really recognize sex matters, hormones matter, and that the fact that they matter doesn't mean that one is necessarily better than the other.

It just means that they're different.

And I think that if we start with that as a starting point, it will actually get us a whole lot farther than where we are currently.

Is modern feminism ignoring or overlooking biology by ignoring the cycle?

I mean, I think that there's certain elements of it, right?

Because I feel like there's like a new new feminism, right?

It's just peri-maternal feminists of the world.

Which is like, hey, you know what?

Men and women are different.

And that doesn't mean that we need to, you know, that one is better than the other, but there are differences.

And it's okay, for example, if you're a woman and you want to stay home with your kids, like, that's okay, right?

Like, whereas the old school feminism was like, women and men are the same.

And if you are a woman and you want to do any of these, you know, quote-unquote, stereotypically female things, it means that you've somehow failed, right?

Or have been brainwashed by the patriarchy.

And I do think that like true feminism is just embracing, you know, the idea that, yes, biologically, sex does matter, but that doesn't need to be limiting, right?

So sex is, it matters, but it doesn't need to be defining.

It doesn't need to be prescriptive, you know, even, you know, gender is something that I think matters in, but it's different than sex, you know, and

yeah.

There was a

study that was done,

a set of research that you would have come across, which was

women,

female hunter-gatherers did just as much big game hunting as men did.

And it was a reassessment of some old data that had already existed.

And this particular group decided that they were going to look at hunter-gatherer data around how much women contributed to big game hunting.

And with their assessment of the data, they did just as much and in some cases, even more.

And I always thought about this, and I thought it was so interesting.

And it

is similar to a lot of the denials of sex differences that we see in the modern world as well.

And I came up with this name, the soft bigotry of male expectations, which is there is this assumption among sort of high-powered modern women, especially sort of the of the boss bitch type,

that whatever men

do or can do or tend to do is the desirable thing or the

set point.

And that women are somehow, when you actually think about the subtext of what they're saying, deficient by not doing that, that it is desirable to do what the men did.

And the fact that we don't need to be addressed so that women can do what the men did, not the other way around, that what the women do is in some way superior.

So for instance, this study that was done, they fucked with the data for a very long time.

It was one

incident or one level, one contribution to a big game hunt was you are a big big game hunter.

It didn't account for the number of times that this happened.

So, men would go out on the hunt a lot, women would have gone out once, and that would have been one for one.

Uh, also, the size of the hunt and the size of the animal that was brought down wasn't brought into account.

The total amount of calories that were expended, whether it was done with small rabbits, like women were typically getting small rabbits doing the gathering, men were still doing the hunt.

It was there was a lot of fuckery that went on.

And it just made me think: like,

who's to say that gathering the berries is less important than killing the wildebeest?

And it's this very strange kind of

like sex seppuku, reverse sexism, but the calls coming from inside of the house.

It's like you're doing this to yourself.

Like you're derogating your own sex's innate tendency.

And it's the same thing with the, well, you, I mean, you've been conned by the patriarchy into being a domestic servant there.

And it's like, that's called being a mother.

And I quite like doing that thing for some women.

But no, because men tend to go out and tend to work, it's seen that that is the sort of desirable thing to go toward.

And it's just a real interesting time where

I can see why this would make it quite unpopular to talk about, well, women have these phases and women change, because again, the soft bigotry of male expectations, men don't have these changes across the month.

Maybe it's actually desirable for women to be on the pill so that they can be more predictable.

They can flatten out that hormonal change.

And that means that they don't need to ride the wave.

And

I hope that changes.

I think it's denying

it's first off, it's making women like insufficient and inferior just by the narrative.

Like, it's not exactly helping women to feel like, oh, I am a whole person.

It's like, oh, I'm like a broken man

whilst also being told in culture that I'm men, but better.

I'd like to square that circle for me.

Yeah, it's just a real interesting thing.

And I don't think that it's particularly good.

Yeah, no, I agree.

And you said it well.

I mean, it's like we talked about with the hormones, right?

It's this idea that having one primary sex hormone is the right way to be, right?

And that there's something wrong with the fact that our cycle and that that's something that we need to be afraid of.

And it all just assumes, as you said, that

male is equals superior and that female equals broken.

Yeah, yeah, and that female equals broken.

And so part of the book is really trying to change that narrative and

say, like,

this is what it means to be us.

And I also spend a lot of time talking about why that's not a dangerous idea, you know, and and that there is, you know, we need to, we need to change the narrative around what it means to have cycling hormones because it's not lesser, right?

And as I said before, there is very much, you can make the case that it's better.

You know, it's just like nobody even thought to make that case because everybody's just assumed that the male way of being is the way to be.

It's time to stop that.

Why?

Why is this area so

understudied?

Like, what is it?

Why did you have to do all this research?

It seems to me, like, given that pretty much every woman, every female at some point will, even if they start taking the pill after their first period, they've gone through one of them, right?

To alert them, oh, hey, by the way, you've hit puberty.

Why?

Why you?

Why does this not already exist?

Right.

Well, I mean, honestly, a lot of it has to do with the history of science.

And I'm not going to give you a big, long, boring history lesson, but I'll say that

when when science started as in in medicine you know sort of in tandem

the assumption was that you know the female body and the male body are essentially indistinguishable from one another minus the reproductive organs right so it's this idea of like you know bikini medicine right this idea that everything else is the same except for boobs and and you know penises and vaginas but then all the rest is the same

And so in science, then, you know, researchers for a long time just studied men.

And it was easier to study men.

They didn't have to worry about whether a man was pregnant.

So you wouldn't have to worry if he was carrying, you know, a baby that could be affected by whatever the experiment was.

And also because men don't cycle, it meant that any man that you came, you know, had come in on a given day and you give him a drug.

And then if you have a different man come in on a different day, that they're going to be more or less the same.

Whereas if you have two women come in, right, one might be in the first two weeks in her cycle.

The other one might be in the second two weeks of her cycle.

And God only knows what would happen next, right?

They might be different from one another.

So, everybody assumed: all right, women are just smaller, you know, smaller men with boobs.

And so, we'll just study men and then we'll apply what we learn to women.

And, um, and of course, you know, that created some problems.

Um, and and it also created um, not only problems in terms of, you know, research results not mapping on to women, um, it created political problems where people were saying, you know, we need to like women need to be in research.

So, researchers are like, oh, yeah, you know, yeah, like we're, you know, we're feminist, we want to include women in research, so let's do that.

And so rather than studying women like women,

which would mean studying the fact that our hormones change and that as our hormones change, that we change, what researchers decided to do is to try to fit female subjects into a way of doing science that was built around men.

Right.

And so rather than including women as research subjects, both in the follicular phase when estrogen is the dominant hormone, and then also studying them later in the progestogenic,

in the luteal phase when progesterone is the dominant hormone.

Instead, researchers only study women generally in biomedical research during the first nine days of the menstrual cycle when hormone levels are low.

And so they only study women when hormones are low to make sure that women are maximally like men.

All right.

And when they study female mice, they overectomize them.

So they actually take out their ovaries so they won't produce hormones.

so here scientists are patting themselves on the back for final look we're including women and female subjects in research right but they're essentially removing our hormones from the research and the results of that i mean and and so it's like we downplayed hormonal influence on behavior for political reasons, right?

For the reasons that we talked about.

We just assume that men are superior.

And therefore, you know, if you cycle and have cycling hormones, there must be something wrong with that because it's, you know, it's not male, right?

And so there's that.

And then it just made things easier for scientists to assume that men and women are essentially the same.

And so, you know, since women are just men with some lady hormones, let's just statistically control for those lady hormones.

So that way, everybody in our research study acts the same way.

And so the result of this is, is that like we've had this mass, you know, delusion into believing that our hormones don't matter, right?

And that they're not an integral part of who we are.

And I mean, the result of it is like women have been absolutely mismanaged in science and then also in medicine it's like when we're included at all as research subjects it's either with our ovaries taken out if we're a female mouse or um or in the first couple of days of the menstrual cycle when hormone levels are low so we know very little about how women respond to anything during the second half of the menstrual cycle.

And it's completely ridiculous.

Because when you look at, and I've got a whole chapter on this in the book, when you look at the full cascade of changes that happen physiologically to the female body in the second half of the cycle, there's every reason to believe that everything ranging from, you know, to our responses to anesthesia to our responses to surgery, to our responses to prescription drugs are going to be a little bit different in the last two weeks than they are in the first two weeks.

And instead of studying it, researchers decided to ignore it.

And so I guess that the short answer is convenience.

What are the implications of this for women?

What would you say to someone who's just had their mind blown about the way that their own hormones work?

How should they show up in a different way to be more effective?

I mean, honestly, I think that the first thing that they need to do is just get a better grasp of their own personal relationship to their hormonal changes.

Because everybody, you know, even though the average response, for example, to the peak in estrogen that women experience near high fertility is to feel really good and have high energy and high sexual desire, there is about 8 to 10% of the population that feels terrible at that time.

And that's actually when they feel their worst.

And so if you're one of those women, and nobody nobody knows why, by the way, it's just, it's interesting.

There's a lot of idiosyncrasy in the way that we respond to our hormones.

And so just to start tracking your cycle and how you're feeling on things that are important to you.

So things like energy level, sexual desire, just how good you feel about yourself, your appetite, your sleep, et cetera.

Tracking that over the course of a couple of cycles to start to understand your relationship with your hormones.

And then being able to, and you can use this with recommendations I make in the book, because I talk about how our needs shift from one phase of the cycle to the other.

And And I do make some recommendations about things that you can do to try to, if you're having, for example, low energy in the second half of the cycle, some of the things that research supports can be really supportive in terms of maintaining high energy levels during that time or the changes in sexual desire and so on and so forth.

And so just like really getting dialed in with what your own body's relationship is with your hormonal changes.

So that way, A, you better understand yourself.

B, you can better communicate about what's going on with you, with people who are important to you.

And then, lastly, so that way you can take any steps necessary to make that transition more like sort of riding a wave instead of falling off a cliff.

So good.

I'm going to be fascinated to see what happens with hormonal birth control use over the next decade or so.

You know, how much of the research that you highlighted is going to be replicated and become even more popular.

And

I guess that means that this stuff is going to become ever more important because more women are going to be at the mercy of those monthly swings.

Yeah, you know, it's funny because one of the things that really inspired me to write this book is: one, I'd been chewing on this question for a really long time.

Just as a biologist, it's a really interesting question to ask why, you know, women should feel terrible half the time.

But also, one of the things that I heard a lot from women who read my first book and decided that they were going to begin naturally cycling and living that way instead of on the pill is that they absolutely loved how they felt during the first half of the cycle when estrogen was high but then during the second half of the cycle they were feeling a little bit lost in the woods right and they were feeling like they fell off a cliff and that they couldn't understand like what you know what am i feeling now is this normal um and so i you know the hope is that this book will help women have a guidebook to the second half of the cycle because it just isn't something that's generally provided um either you know in the cultural conversation, right?

Like if we, if you and I go on TikTok and look at all the videos about hormones, it's all about estrogen.

You know, it's like we've heard and like we know so much about estrogen, estrogen, this, estrogen that.

And so, this is really trying to provide that blueprint and that guidebook to the second half of the cycle.

Um, so that way women can have a like a really great, like full 28 days of the cycle instead of just the first 14.

Awesome.

Dr.

Sarah Hill, ladies and gentlemen.

Sarah, where should people go?

They're going to want to check out all of your stuff online.

Um, my website is saraehill.com, and that's Sarah with an H, as it always should be.

Sorry, Sarah with an A.

And then Sarah E.

Hill, PhD, on all platforms.

I'm most active on Instagram.

Heck yeah.

Sarah, I appreciate you.

Until the next time that you come and upend everybody's world with some more research.

Thanks, Chris.