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Always look on the bright side of life

This story was originally published by Knowable Magazine.

A sunny disposition isn’t just good for your mental health. It’s
good for your body, too. It can even add years to your life.
Sarah Pressman, a health psychologist at the
University of California, Irvine, has spent her career
investigating the link between positive emotions and physical

In the 2019 Annual Review of Psychology, she and her
colleagues explore why a positive outlook generates physical health
. Knowable asked her about some of the high points, and
how doctors and their patients can make use of the knowledge. This
conversation has been edited for length and clarity.

How did you get interested in studying

For decades, researchers have been studying all the detrimental
ways that stress can make us sick and lead to pain, and minor and
major illness. As a graduate student, I got interested in the
opposite: What can protect our bodies against the harmful effects
of stress? At that time, in the early 2000s, the field of positive
psychology was really just starting. I saw a natural synergy there
— there are these positive factors, and maybe they could be
protective against stress and have health benefits, or at least
protect us against health harm.

And does a positive outlook make a measurable

The negative effect on your health of being socially isolated is
stronger than the effect of being overweight, a regular smoker or a
heavy drinker. That kind of comparison hasn’t been done yet in
positive emotion research. But there’s a host of studies — probably
in the dozens now — that show that people who are
more positive tend to live usually five to 10 years longer
those individuals who are less positive. That’s a pretty large

What causes this effect?

We have a lot of hypotheses. Positive emotion changes our stress
perception so stressors don’t seem as bad. It changes how we react
to stressors, and it helps us recover. Both our stress reaction and
our stress recovery have been shown to predict important outcomes.
Pick a disease — heart disease, for example. If you feel calmer,
your blood pressure is lower, your heart rate is lower. And we know
one of the things that predicts heart disease is arteries blocked
up with plaques. And where do those plaques come from? Partially,
from damage from high-speed, high-pressure blood. If your blood
pressure is lower, and your heart rate is lower, you have less of
that turbulent blood flow, and therefore over time you might have
less damage to arteries and less plaque.

Positive emotions also change how our immune system works. We
don’t know exactly how, but we do know that if I make you feel
positive, if I make you feel calm, we change the numbers of your
immune cells, and we tend to drop your inflammation level. For
example, there’s a marker of inflammation called interleukin 6, or
IL-6. People who are generally more positive, or who are induced to
feel more positive, have lower levels of IL-6.

But even aside from that, when we are feeling positive, we’re
much more likely to engage in healthier behavior. We take better
care of ourselves, we’re more likely to sleep better and exercise,
we have a better diet. People who are more positive tend to have
more relationships, better-quality relationships. They’re more
likely to be married and stay married for longer. If you have good
relationships, those people will encourage you to take care of

That gives us some really compelling pathways for how this can
happen, both on the behavioral end and by directly altering
cardiovascular function, hormonal function, immune function. If I’m
happy today, that doesn’t mean I’m going to live longer. But if I’m
happy for a few years, that might make a difference.

How do we know that positive emotion causes better
health, rather than the other way around?

To do the perfect study would require that we experimentally
assign people to an intervention that makes them happier, or less
happy, and see if that affects longevity. That has not been done.
But we have a lot of studies of groups of people where we know the
health and the emotional state of each person at the start. We
control for sociodemographic factors, we control for medications
and immune function. So we know that those people who were less
happy at the beginning weren’t less happy because they were already more

Then we can look over time. If you control for smoking and
health at the start and you still see the effect of positive
emotion five or 10 years later, it’s more suggestive than a study
looking at people at just one point in time and just saying, “Oh,
happy people feel healthier.”

Graph compares people with low, medium or high score on a test of positivity and how they fared after being purposely exposed to a cold virus. Those with the highest scores were best able to fend off the virus on both an objective measure of infection and a subjective one.

In a classic study, people with a more positive outlook were
less likely to get sick after experimenters introduced cold viruses
into their noses. The researchers measured the volunteers’ sickness
both objectively (by weighing a day’s worth of used tissues) and
subjectively (by asking the volunteers if they had a cold).

Have you also done experiments?

We measured people’s naturally occurring positive emotions. Then
they were experimentally wounded. It was kind of a nasty study,
actually. We damaged their skin by putting tape on it over and over
and ripping the tape off. We monitored to see how quickly water was
being lost from the skin surface. As that water loss decreases, we
know the skin cells are healing. This is really an immune-system
function test, because the more quickly your immune system is able
to traffic white blood cells to the injury, the faster you will
heal. We saw about a 20 percent shorter healing time for those individuals who were more
versus those who were less positive.

There is another study, not yet published, where we manipulated
positive emotion. There’s something called the facial feedback
hypothesis, where if you fake an emotion, it sends a message to
your brain that you’re feeling that emotion. If we trick people
into smiling by holding things in their mouth, it can trigger a
positive emotion.

So we had people smile while getting a fake flu shot. Some
people were smiling and others were not. Those who were smiling had
about 40 percent less pain from that needle, and their heart rate
recovered faster from the stress of it.

Do we know that positive emotions — and not just the
absence of negative ones — are causing the benefit?

That we actually know really, really well. Through the last 20
years of research, almost every study does a good job of accounting
for that by controlling for negative emotions.

Time and time again, you see that it really does seem to be the
presence of positivity, independent of
negativity, that’s driving health effects. It’s the presence of
positive emotions, not the absence of negative ones, that can help
undo stress. If I have to give a talk and I’m feeling neutral, that
isn’t helping me — but if I can say, “Actually, I’m really excited
about giving this talk,” that can change my stress trajectory. That’s
very different than the absence of a negative emotion.

Are there health conditions where a positive attitude
doesn’t help?

For individuals who have a serious chronic illness that’s far
gone — stage 4 cancer, end-stage kidney disease — the data are
inconsistent. Some studies show benefit, some show harm, some show
no effect. If we’re talking about a minute immunological change
from laughing, that’s not going to kill millions of cancer

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On the other hand, if you are feeling hopeful and positive, and
able to adhere to your doctor’s recommendations, and take the
medications that you’re supposed to, and exercise when you’re
supposed to, and quit smoking, those things are helped by positive
emotions, and can have an important role in helping at earlier

This is something we have to work on, because if people want to
design positive interventions for these severe illnesses, we have
to really understand when it will be helpful. That’s a really
important next step for the field.

Isn’t there a risk that people with serious diseases
will be stigmatized into thinking it’s their own fault for not
being more positive?

We certainly don’t want to say that. There’s absolutely no
evidence in health psychology that being unhappy causes cancer, or
causes disease to happen. If someone gets diagnosed with cancer,
you don’t want to tell them to be happy all the time. There’s good
evidence that keeping negative feelings locked up inside is harmful
to our health. They have to go somewhere. You have to let it out —
express your negativity and process it. Once you’ve accomplished
that, we can try to teach you how to find benefit.

It is very important for people to deeply understand the power
of mind over body, because if you are depressed and you are
stressed it can be hurting you, and we want to help you cope with
that. There is value in pursuing happiness. It’s not a selfish,
silly, soft thing that you don’t have to do. This is actually an
important piece of being a healthy human. And at a time when your
health is compromised it can be especially important.

Are there ways to change people’s happiness level?
Aren’t some people innately Eeyores and others Poohs?

Some work suggests that as much as 40 percent to 50 percent of
happiness is based on genetics — you just luck into being born a
more positive person. But that leaves a lot of room to

Illustrations from a picture book show Winnie the Pooh and Eeyore, characters that differ in their natural emotional set point. While Pooh is often optimistic, Eeyore tends to pessimism. Such an affect can influence health, some studies say.

Although some people naturally tend toward a more positive or
negative outlook — like Winnie the Pooh and Eeyore — studies
suggest that happiness is based on much more than genetics or
innate setpoints. Exercise, relationships and personally meaningful
activities can help an Eeyore see the bright side, which may also
impact health.


A good amount of our day-to-day wellbeing — maybe 30 percent to
40 percent — is due to how we choose to spend our time. We can
choose to spend our time on things we know improve positive
emotion, like spending time with the people we love, having good
relationships, getting enough sleep, exercising.

But on top of that, there are some specific, well-researched
interventions — little tweaks that can help you focus on positive
things. We can train our brains to hang onto positive emotions,
which should help promote that positive emotion in our daily lives.
Some of the more popular activities are gratitude exercises, where
before you go to bed you write down three things you’re grateful
for, and meditation.

The nice thing about happiness is you don’t have to buy some
expensive medicine. Much of this is free. Happiness is not just a
luxury that rich people should be pursuing — it’s something that
absolutely everyone should be investing time in every day.

This story was originally published by Knowable Magazine. Knowable Magazine is an independent journalistic endeavor from Annual Reviews.

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