Transcriber: Silvia Monti Reviewer: David DeRuwe
How much do you know about the birth control pill?
Like, really know about the birth control pill?
Now, if you're a woman in the audience, you've probably heard the drill, right?
You have an increased risk of stroke,
or weight gain,
or, you know, you might get a risk of pulmonary embolism,
especially if you're over 35 and smoke, right?
Guys in the audience, you probably know that if your partner is on the pill,
that it might spare you the cruel and unusual fate
of having to wear a condom during sex.
Right?
But, like, how much do you know about the birth control pill
when it comes to the part of our bodies
that most of us care about more than any other?
The brain.
How much do we know about the birth control pill and the brain?
You know, asking this question
is something that feels a little risky to a lot of women,
and this is because to ask this question
violates two rules of feminism
that most of us would adopt sort of unconsciously since childhood.
Right?
And the first of these rules is "do not criticize the birth control pill."
Right?
Women are understandably very protective of the birth control pill.
And the reason for this is that it's been absolutely amazing for women.
And just to illustrate this for you,
if you look at this figure behind me,
what you'll see is the proportion of female applicants
to law and medical schools
prior to the birth control pill being made legally available
to single women.
They made up just 10% of the applicant pool.
Flash forward 20 years later,
and women are 50% of the applicant pool.
By allowing women to regulate their fertility
and be able to plan,
women made longer-term career goals, longer-term educational goals.
And the birth control pill and all the freedom it afforded us
is responsible for so much of women's advancement
in terms of being able to become financially independent from men.
And so the pill has been a really amazing force
in the lives of women.
And because of this,
questioning or thinking critically about the birth control pill
can scare people by making them think that we'll have to go back
to a time when women were financially dependent on men,
and lose some of our freedom,
despite the fact that knowledge is always powerful,
and talking critically about the birth control pill
doesn't mean that we have to give it up.
The second rule that we get into trouble with
when we'd want to talk critically about the birth control pill and the brain
is the rule that tells us
we absolutely cannot talk about sex hormone involvement in the brain,
if you're a woman, right?
And the reason for this is that for a very long time,
women were treated as overly emotional, less rational versions of men
because of our changing sex hormones.
There was a lot of sexist rhetoric
that said that women shouldn't possibly be able to hold important jobs,
own land or vote
because our cyclically changing hormones just made us completely irrational,
and therefore, you know,
not somebody who should be in these types of positions, right?
But this idea prevents us
from being able to have thoughtful discussions about the pill.
And they're also totally not backed up in science.
To start with,
women's hormones change cyclically, but they're not unpredictable.
They're not capricious or whimsical or fickle.
If you tell me a woman's age,
and you tell me the first day of her last menstrual cycle,
I'll be able to predict with an almost alarming amount of precision
exactly what her sex hormones are doing at that moment, right?
If she's in the first half of her cycle,
we'll find that the sex hormone estrogen is relatively high
relative to levels of progesterone.
And if it's the second half of the cycle,
I can predict that progesterone levels are going to be relatively high
relative to levels of estrogen.
So even though women's hormones change cyclically,
they're not unpredictable and capricious.
Men's primary sex hormone, testosterone, on the other hand,
is a totally different story, right?
So we know from research
that men's levels of testosterone change in response to age, time of day,
whether or not he has children,
whether or not he's just watched sports,
whether or not he's passed weapons -
like, if you see a gun, that changes testosterone levels -
the presence of attractive women
and a whole bunch of other stuff too.
Okay, so if anybody's got capricious hormones,
it's men, right?
(Cheers)
(Applause)
So -
(Applause)
So the idea
that our sex hormones influence our brain shouldn't be problematic, right?
Women's hormones change, and they influence women's behavior
and how women think, feel and what they do.
Men's hormones change,
and when they change they also influence what men think, feel and do.
And we have to start having conversations about these things
because not doing so is bad for women's health.
Because we need to break these rules
that have prevented us from having thoughtful conversations
about the birth control pill and who it makes women.
Because even though women take the birth control pill
for a small number of targeted effects,
it has an impact on women's bodies from head to toe,
including the brain.
And the way that the birth control pill works
is it changes women's levels of sex hormones.
And even though we tend to think of our sex hormones
as something that happens to us,
or like something that causes puberty and hair growth
in places that we don't really want to talk about in polite company,
our sex hormones are actually a key part of the signaling machinery
that our brain uses
to create the experience of being the person that we are.
And so when we change women's sex hormones,
we're actually changing the version of their brain
that they are creating.
And there's a growing body of research in psychology and neuroscience
that shows this to be true.
For example, just thinking about sexual functioning,
which is something that we all think about a lot,
we know from research
that women who are on the birth control pill
exhibit decreased sexual desire and decreased sexual functioning
relative to their naturally cycling counterparts.
And the reason for this has everything to do
with a hormonal profile that's created by the birth control pill.
The hormones that facilitate the sexual response in women
and facilitate sexual desire
are relatively high levels of estrogen and testosterone
and lower levels of progesterone.
Progesterone actually inhibits women's sexual desire.
And the sex hormone profile on the birth control pill
is essentially sexual anti-venom, right?
It's a high level of progesterone, a sexual inhibitor,
and relatively low levels of estrogen and testosterone.
And indeed there's a lot of research
indicating that women tend to have diminished libido
when on the birth control pill.
But it's not just sexual desire
and women's desire for sex and their sexual responsiveness
that changes in response to the birth control pill.
It can also influence who women are attracted to, right?
And this is also something
that's influenced by the levels of sex hormones
that are created by the birth control pill.
So we know now from decades of research
that women's own levels of estrogen
predict the amount of testosterone that they prefer in their partners.
In other words,
the sex hormone estrogen increases women's attunement to cues
that have historically been linked to testosterone levels in men.
This graph that you're looking at here
is showing how women's own levels of estrogen
predict testosterone preference.
And what you can see from this
is that estrogen loves testosterone.
So women when they have relatively high levels of estrogen
are really cued into facial cues that are associated with masculinity.
And this changes their preferences over the course of the cycle.
Now, given that the birth control pill keeps levels of estrogen very low,
we can make the prediction
that women who are on the birth control pill
should prefer as partners
men who have fewer cues associated with testosterone preference.
And that's exactly what we find.
And so research finds now
that women who are on the birth control pill
prefer partners with less masculine faces than their naturally cycling peers.
And this is something that is found
both when women are identifying men
that they would like to have as short-term sexual partners
and also the people that they'd like to have
as long-term romantic partners, right?
The research has also found
that pill-taking women are actually choosing as partners
men with less masculine faces relative to naturally cycling women.
So they've done studies
where they've brought in the partners of women who chose their partner
whether they were on or off of the birth control pill,
took photographs of their faces,
created facial composites,
and they were able to actually look at the proportion
of testosterone markers and the faces of men.
And they found out
that the pill-taking women, indeed, were choosing as partners
men with fewer testosterone markers in their faces.
So the birth control pill might be changing the face of mate preferences.
And it's not just sex and sex-related things.
Sex and mating -
it all makes sense that all of that should change
in response to the birth control pill
when we really think about the idea that it's changing women's sex hormones.
But that's just scratching the surface
because our sex hormones also influence the other hormones in our body,
including those that are associated with our stress response.
So stress is something we all know, right?
You know stress -
sitting in traffic, giving a TED Talk in front of a thousand people,
being on the business end of a wildebeest stampede, right,
daily things that happen to us.
Wherever we are in the world,
there'll always be a wildebeest stampede, right?
Anytime that we're encountering a stressor -
no matter what it is,
whether it's a TED Talk or the wildebeest -
generally within about five minutes
our body releases the stress hormone cortisol,
which tends to get kind of a bad rap,
because everybody associates it with stress,
but cortisol isn't what causes stress.
Life is what causes stress.
Cortisol is actually part of the way that our body helps cope with stress.
It dumps fat and sugar into our bloodstream
so we can make a fast getaway,
and it primes our brain for learning and memory,
so that way, if we encounter a similar situation in the future,
we'll be better able to cope with it.
Because of this, when we're feeling stressed out,
our body releases cortisol ...
unless you're on the birth control pill.
So there's several decades of research now that shows
that women who are on the birth control pill
exhibit a blunted or altogether absent cortisol response to stress.
And this is something that's potentially really important,
and not only because this is the type of profile
that we tend to see in people who've undergone trauma or have PTSD,
but also because it can cause structural changes in the brain,
decrease people's ability to cope with stress,
cause problems with emotional regulation
and impair learning and memory.
And there's some research now coming out about the birth control pill
in each one of these processes
that suggests that we might be seeing just these patterns
in women who are on the birth control pill.
And it's not just individual women
who are changed by the birth control pill.
Each woman lives in an interdependent web
that includes her friends, her family members,
her romantic partners and her colleagues.
And so when we change what women's sex hormones are doing,
those changes are going to echo throughout the woman's body
in ways that have a lot of effects on her system,
but they're also going to echo throughout the world
as women are interacting with other people and changing the face of the world.
So it's time to throw out the old rules,
and we need to start having more, not fewer conversations
about women's brains and the birth control pill.
And this doesn't mean that we abandon the birth control pill, right?
It's still going to be the best choice for a lot of women
at certain points in their lives.
It was my choice for over a decade.
But it's time to put the power of information in the hands of women
to let them know what trade-offs
they're making with the birth control pill,
so that way they can make informed choices
about their health and who they most want to be.
Thank you.
(Applause)