Stress in animals and humans | Lauren Chaby | TEDxLancaster

Lauren Chaby, a Neuroscience Ph.D. candidate at Penn State, talks about the impacts of developmental stress in humans and animals. Her talk creates a better understanding of the causes of stress as well as what we can do to reduce stress in our lives.

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

Gunter joined the military
at an early age.

Eventually, he was deployed
to Afghanistan to help detect bombs.

At first, Gunter's behavior seemed normal,

but soon he was experiencing
incredible anxiety.

He wasn't able to follow commands
or complete his missions,

and after nearly a year of retraining,

he was sent home.

He had some trouble
integrating back into society.

He was still anxious and hypervigilant.

His family was concerned, but patient.

Pretty familiar story, right? Not unusual?

What if I told you that Gunter is a dog?

In the past few years,

there have been over 50 similar cases
reported by the military

where dogs show extreme
responses to combat.

In Gunter's case,

his military handler believed that he had
canine post-traumatic stress disorder,

or PTSD.

So, why is Gunter's story important?

Well, there are similarities
and differences

in how humans and other animals
respond to stress,

but what's really significant here
is that we are not the only ones

that can have these extreme
responses to adversity.

Other species can, too.

So, while stories of shell-shocked dogs
have spread through popular media,

the possibility that other animals
might be susceptible

to pathologies like PTSD

has become a topic
of heated debate in science.

Some scientists suggest

that PTSD may be an extreme version
of an anti-predator response.

There are few things in an animal's world
more salient than predation threats,

and they may get only one chance
to learn about these threats.

Supporting this is the idea

that many of the symptoms of PTSD overlap
with normal anti-predator behaviors,

like increased anxiety,
quick startle responses,

and hypervigilance.

The reality is that stress
can change your brain.

It can change cells in your brain and how
these cells communicate with one another.

In brain regions important
for learning and memory,

cells can shrink and become
more vulnerable to future challenges.

In brain regions important
for modulating fear,

cells can grow and become
better connected.

Over time, stress can have devastating
effects on health and behavior,

and many of us know this
from personal experience,

but what's new is the realization

that animals can experience
the effects of stress

much more like ourselves
than many believed possible.

My colleagues and I
at Penn State have found

that, even if stress occurs
relatively early in life,

animals still show increases in anxiety,

changes in the way they make decisions,

changes in the way
they face future challenges,

and differences in the very way that they
perceive the environment around them.

These changes are present
for the majority of their life span.

But animals do experience
stress differently,

and by understanding those differences
between how species process stress

we can better understand how evolution
shaped our own stress response.

One important feature
that we share with other animals,

in how we regulate stress,

is our body's ability to shut off
the production of stress hormones,

that is integral in our ability
to recover from challenges.

When we are under chronic stress,
this shut-off system can become faulty.

We produce our own marinade
of toxic hormones

that can suppress immune function,

can kill brain cells, impair cognition,

and suppress fertility.

The consequences
can truly be life-changing.

It's even suggested
that this may contribute to aging.

But in one of the cases of the most
extreme stress in a natural system,

we don't see a reduction in the ability
to shut off stress hormones.

Take a look at a classic example

of predator-prey interactions
on record since the 1800s.

Lynx and snowshoe hare populations
rise and fall together.

At some point in this cycle,

populations of over 80,000 hares
are nearly wiped out by lynx predators.

With the hares gone, so goes the food,
and soon the lynx start to die out, too,

but before they go, they can kill
up to 90% of the hares.

But those hares that remain, those few,

still don't show this reduction
in the ability to turn off hormones

that we see in humans.

One feature of the stress response
that we do see in other animals

is that offspring born to mothers
under high-stress environments

can show a very familiar set of symptoms:

increased anxiety,
quick startle responses,

and hypervigilance.

These animals are reacting
to a high-stress environment

without ever having seen
the environment themselves.

It's believed that, when stress
has effects like this,

from a mother to her offspring,

stress hormones may be acting as mediators

to prepare that next generation
to face challenges.

So, the question becomes:

why are humans and animals
responding differently?

Well, we don't know yet,

but what we do know is that differences
between species in how they process stress

can help us to better understand
our own stress response.

The roots of our current pathologies
evolved in natural systems,

and we can study those natural systems

to better understand how and why
these extreme responses came about.

Regardless of whether or not you believe

that a dog can experience something
as complicated as PTSD,

there are cases in other species

where individuals, like some of us,
show these extreme responses to stress,

and we can better understand
those individuals

and better understand ourselves.

So, what does this mean for us?

Well, unfortunately,

there's stigma associated
with mental illnesses,

including PTSD,

but it's important to remember

that PTSD is linked to a biological,
adaptive response

that evolved for dealing
with life-threatening situations.

A shift in the mindset may help
to overcome these negative stereotypes

associated with mental illnesses.

The reality is stress
can change your brain.

It's a scary thought,
but here's the good news:

you can fight back,
you can change your brain, too.

There are a number of ways
to combat the effects of stress.

Here are two of the easiest.

The first is exercise.

Exercise can do great
things for your brain

to directly oppose changes from stress.

Exercise can increase cell density

and promote survival
of cells in your brain

in the very same regions
targeted by stress.

Exercise can also keep cells that control
blood pressure from growing unchecked.

Just 20 minutes of aerobic exercise,
three times a week,

can help change your brain enough
to offset the effects of stress.

A second way to alleviate
the effects of stress

is to simply see someone
with expertise in this area.

A skilled cognitive therapist
can help you change your brain

to strengthen the connections
that suppress fear responses.

You can limit the impact
of stress in your life

by simply controlling
how you respond to it.

As for Gunter,

we now know that, by better understanding
his extreme response to stress,

we can better understand ourselves,

and we can help those like Gunter,
who have suffered from trauma,

to live beyond their experiences.

You can mitigate the effects of stress
by simply controlling how you respond,

and you can limit the impact
of stress on your mind and your body.

(Applause)