The surprising link between women's brains and the birth control pill | Sarah E. Hill | TEDxVienna

The birth control pill changes women's brains. Because of this, it changes women, and often in surprising ways. This talk will teach listeners about what science knows about the pill and the brain, empowering women to make informed health choices.

Sarah Hill is a research psychologist who studies women, psychology, and health using theoretical tools made available from the evolutionary sciences. She has published dozens of papers on topics like eating, sexual behavior, inflammation, and romantic relationships. Recently, she has turned her expertise to uncovering what we know and don't know about the impact of the birth control pill on the brain.

This talk was given at a TEDx event using the TED conference format but independently organized by a local community. Learn more at https://www.ted.com/tedx

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)