Translator: esther premkumar Reviewer: Robert Tucker
Stress can get under our skin,
it's not just a feeling or an emotion that passes over us,
stress has consequences.
My name is Natalie Riddell.
I'm a lecturer in immunology and ageing,
and I study how stress can affect the immune system.
I'm interested in how stress can change the way
that we respond to infections and cancers.
And I believe that if we can understand how stress changes the immune system,
and how it regulates the immune system,
we may be able to manipulate and control our immune response to stress.
And this may help us promote better health outcomes.
During stress, two hormones are released: adrenaline and cortisol.
And both these hormones can directly act upon the immune system.
And this means that these hormones can impact upon health.
They can do many things to the immune system,
including changing the number of cells that are in our blood,
or in our organs,
and also changing the way
that these cells respond and recognize things such as infections and cancers.
The levels of these hormones change throughout the day,
depending on what time of day it is.
They have circadian rhythm,
and this is thought to promote immune activation during the day,
which will protect us and promote tissue repair and regeneration overnight
when we are at rest.
And one of the consequences of stress
is that it can alter this circadian rhythm,
and this can then impact health.
So, why do we think that stress is bad?
Most people have either been stressed their self
or know someone who has been stressed,
who has then become ill.
But there is also scientific evidence to support this.
In the 1970s, Holmes and Rahe developed a stress scale.
They took over 14 normal life events,
some of them quite major life events,
like losing a loved one or otherwise relationship breakups,
and some not so major life events such as Christmas.
They gave each of these different stresses a stress score,
they tallied up the amount of stress
that a person had experienced in the previous year,
and this was able to predict
the likelihood of illness in those individuals.
So, this really showed
that there is an association between stress and health outcomes.
And stress doesn't just affect the individual,
it also can affect and have a huge impact on society.
The Health and Safety Executive,
who monitor and regulate the health of the workforce here in Great Britain,
found in 2006
that the second most commonly reported reason for ill health
was because of stress.
This equated to 45% of all workdays lost due to ill health.
That's 11.7 million sick days.
And these numbers could actually be a lot larger
because most people won't actually report
that the reason that they are off work is because of stress.
Because there is such a stigma associated with stress and mental health.
And even quite mundane daily life events can cause stress.
Today, I was stuck in traffic and I became quite irritated.
I also get really embarrassed if I forget somebody's name.
And even the social expectations that we put upon ourselves,
and put upon each other,
can cause a stress response.
And this is becoming ever more prevalent in a world of social media
where we're constantly exposed 24/7.
And each of these stresses, although very different,
causes the same stress response.
There is one theory from evolutionary psychologists
that we have a stone-age brain.
This doesn't mean that our brain has not evolved at all since the stone age,
just that it hasn't adapted enough.
And this could be true for the stress response.
You can imagine that the types of stresses we face in the modern world
are very different to our cavemen ancestors.
So, it is possible that our adaptation to stress
does not serve us well
when we are considering the modern day stresses.
So stress, it's a big thing.
It's an important part of our biology.
So, how can we define stress?
In the 1960s, the psychologist Richard S. Lazarus
defined stress as being an association between appraisal and coping.
So, when a stressful event occurs,
we assess our ability and our resources to deal with that stressful event.
If we believe that we can cope, then everything is fine.
But, if not, we become stressed.
Put simply, it's a situation or an event
that exceeds or is perceived to exceed our ability to cope.
And this results in an emotional response and a biological adaptation,
such as anxiety and activation of the sympathetic nervous system.
So, stress is something of an event that is out of our control,
that we feel we can't cope with, and causes a biological adaptation.
Our biological adaptation is activation of your sympathetic nervous system.
And, as you can see from this diagram here,
the sympathetic nervous system innervates many organs throughout the body.
This means that during stress many physiological adaptations occur,
including an increase in our heart rate, an increase in respiratory rate,
and also greater energy production.
And this all allows increased physical capacity
for the individual to cope with whatever the stressor is.
So, it's a good thing, it's our fight and flight response,
it promotes the survival of the individual.
We also see stimulation of the adrenal glands
and this results in the release of the hormones adrenaline and cortisol.
And these are released directly into the blood
where they are able to then circulate and act throughout the body.
Each and every one of the organs of the immune system are innervated
by the sympathetic nervous system.
This means they are under regulation of the sympathetic nervous system
during stress.
Also, each of the cells of the immune system
expresses adrenergic receptors and glucocorticoid receptors.
This makes them responsive to adrenaline and cortisol.
For example, every process of the immune system
is affected by stress.
So, for example, the development of newer cells in the bone marrow
is altered during stress.
Also, the initiation of immune response to stress in the lymph nodes is affected.
And the cells, when they are out in the peripheral tissues,
such as the lungs, or the guts or the skin,
they are also affected by adrenaline and cortisol.
So, considering that the stress adaptation response
is meant to be a beneficial response that promotes our survival,
we would expect the immune system response to stress
to also promote survival of the individual.
And that is indeed what happens during acute psychological stress.
So stresses that last just for minutes or hours.
So, as I'm stood here in front of you today,
I'm having a stress response.
My heart rate is through the roof, adrenaline is rushing through my veins,
and so are a very large number of immune cells.
As you can see from this graph, during acute stress -
this data was from individuals that were given a 10 minute talking task,
or doing a 10 minute talking task -
you can see that the stressor almost more than doubled
the amount of immune cells present in the peripheral blood,
compared to blood samples taken at base line
when the person wasn't stressed.
And as soon as the stress finishes,
the number of immune cells in the blood returns to normal.
And what my work and work by others has shown
is that not all cells respond during stress.
Only the soldiers of the immune system respond.
These are the cells that are able to migrate into the inflamed tissues,
and, once there, they can immediately eradicate
any infections they come in contact with.
So acute psychological stress does boost our immune system.
It promotes a protection against infections.
And this, we believe, will promote the survival of the individual.
However, most common day stressors
don't actually, or, nowadays, do not,
come with the threat of infection and injury.
So, how does the physiological response to stress manifest in the modern era?
Imagine that an individual has an underlying and inflammatory condition.
When they become stressed,
they see this increase in the soldiers of their immune system surveying the body.
This could aggravate the inflammatory condition that they have.
And what happens if the stress doesn't last only for minutes or hours?
What if it goes on for weeks, or months, or even years?
The stress adaptation response did not evolve to last for that long
and, consequently, it can't.
In the 1930s, Hans Selye, recognized this,
and he described three stages of the general adaptation syndrome.
The first stage was the stress response.
This is when the individual has a fight and flight response.
But we can't maintain this level of excitement for a long time.
We then move into a state of adaptation.
This is where the body builds up resistance to the stress.
And finally, if the stress becomes chronic,
then we become exhausted, the system becomes exhausted.
And it's when this exhausted state is reached that we become ill.
The immune system is a delicate balance
between immune protection against infections and cancers,
and immune regulation which will prevent inflammatory disorders:
it stops self-harm, it stops an overzealous immune response,
so it will stop autoimmune diseases.
What we see during chronic stress is the worst of both worlds.
We see a loss of this balance,
and we see decreased immune protection, and we see increased inflammation.
And this is very similar to what we see within old individuals
when we look at their immune system.
So this may suggest that chronic stress
can also promote premature ageing of the immune system.
So, we believe that chronic stress,
via this loss of normal immune regulation and by ageing the immune system,
may mediate the association
between stress and increase incidences of infections, malignancies,
and also inflammatory conditions.
So, chronic stress is a good thing that has gone bad.
The stress adaptation response was originally a good thing,
but when it becomes chronic, it becomes a bad thing.
But we can't stop stress, we can't stop it happening.
But, as stress only occurs
when an individual perceives that they cannot cope,
it may be able to teach resilience to the threat.
And our best weapon against stress is social intervention.
In studies of caregivers with spouses with dementia,
we found that their immune system is suppressed.
If you give caregivers a vaccination, they have a reduced immune response.
But the level of this reduction is directly correlated
to how much social support they feel they have.
Those individuals with very little social support
have a worse immune response to vaccination
than those who have higher social support.
And in the individuals that have very little social support,
if you actually provide them with a support network,
their immune system and their immune response improves.
Or if you engage them in therapy, such as mind-body therapies,
this can also improve their immune response.
So we really have a window here
where we can increase social engagement at work
or we can provide support networks to isolated vulnerable people in society.
And we may be able to improve their immune function
and improve their overall wellbeing.
Usually, prevention is better than cure.
And one way we can try to prevent stress
is by teaching people to understand and manage their stress.
For example, teaching people mindfulness
can actually improve their cognitive function
and their overall wellbeing.
And this has been demonstrated in student populations, military personal,
and also in cancer patients.
And teaching emotional intelligence,
the importance of it is now becoming recognized,
so it's now being taught in some schools.
And the Healthy and Safety Executive
has placed stress management as one of their top three priorities.
And this is because of the condemning figures I showed you earlier,
demonstrating that stress
is now the second most common cause of work related illness.
And we need to talk about stress.
We need people to understand
that the stress response is a normal physiological response,
and, hopefully, this will help remove the stigma associated with stress.
And we need to engage the policy makers.
We know that the physiological response to chronic stress
is causing ill health in individuals.
It's associated with some of the most common diseases
facing the modern world,
such as heart disease and dementia.
These are some of the biggest killers currently in society.
But despite this,
and despite the fact that stress management is easy and affordable to do
compared to other medical in[ter]ventions,
we don't try to manage stress nearly enough.
So we really need to encourage the policy makers to take stress seriously
and put it upon the agenda.
I truly believe that by managing stress and teaching people resilience,
we will be able to promote health and wellbeing
in everyone from children right through to the elderly.
And this will help people be the best they can and feel the best they can.
Thank you very much for listening.
(Applause)