Lecture 5.1: Stress and Illness


In this lecture we’re going to
take a look at stress and its impacts on health and
particularly its impacts on illness, and some of the ways in
which stress goes about having an impact on health and illness. We know from years and decades
of research that stress has a prominent impact
on health outcomes. In general more stress
tends to lead to worse health. Specific health outcomes to
the individuals though are determined by interaction
vulnerabilities and stress. What we often refer to as
the diathesis stress model. In the diathesis stress model we
presume that there are certain diathesis, or vulnerabilities
that when people are exposed to can produce outcomes. Examples of diathesis would
be exposure to a cold virus, perhaps a family
history of obesity, or a family history of a body
that produces high cholesterol. Those are vulnerabilities,
but often those vulnerabilities aren’t exposed, or aren’t
activated unless under periods of stress. So individuals, well frankly
everybody gets exposed to the cold virus, we’ve been
going through that in the fall, but it’s only those people who
are under stress that are at most risk for
developing the outcome, which are the developing of
the symptoms of the common cold. Likewise for people with a
family history of obesity or a body that produces
high cholesterol, it’s really only under
stress that the highest risk is appreciated for developing
obesity or developing culinary heart disease. So the diathesis stress model is
an important model for helping us understand why although
people are exposed to many vulnerabilities, they don’t
all go on to develop the same disease outcomes. Stress is an important
moderator of that effect, you’ll remember
that term, moderation, from earlier lectures. So how exactly can
stress impact health? Well there’s at least two ways,
two major ways that stress can come to impact health. First stress can
impact behavior itself, and so stress sort of indirectly
through changing our health behaviors, increasing for
example things like excess in fat in our diet, or
sugars and carbohydrates, increases in substance use
like tobacco or alcohol, or reckless behavior
that leads to accidents. It might decrease a diet rich
in fruits and vegetables or decrease physical activity
and interfere with sleep. Stress can also impact health
through directly impacting physiology, things like
increasing blood pressure, or increasing unfavorable
lipids in the blood stream. Could also decrease the
function of the immune system, which we’ll touch on
in a different lecture. So looking first at
stress and health behaviors, we know that stress influence
health indirectly through the influence of changing health
behaviors that we know are related to health outcome. Individuals with high stress
tend to increase things that are bad for health. Consumption of a higher fat diet
tends to occur under periods of high stress. Increased use of
tobacco or tobacco products, increased used of alcohol or
other intoxicating substances as a way of coping with stress
is certainly a possibility. And lastly people under high
stress tend to engage in riskier behavior and
experience more accidents. Fascinating research today is
looking at the mirror biology of this and how part of our
stress response is designed to encourage us to take risks, part
of that is part of that fight or flight response that you may
need to do things under periods of stress when faced
with a predator to survive, so the brain is prompted
to take riskier behaviors. But things that we do in the
modern world that might be prompted by that are things like
perhaps driving more recklessly, and so by engaging in riskier
behavior we may experience more accidents. We also know that individuals
experiencing high stress tend to decrease a number of
health protective behaviors. They tend to decrease
consumption of fruits and vegetables, you may notice
that many of the things that we consider comfort foods in our
daily diet are higher fat foods that are lower in nutrients like
fresh fruits and vegetables. That’s not by accident, that
tends to be a diet that is promoted by the
stressed response. We tend to decrease
physical exercise and activity. Many people under
stress in the modern world, much of that stress
is time pressure, and time pressure often squeezes
out periods of activity like walking or aerobic exercise. And lastly we know high stress
tends to decrease both sleep quantity and sleep quality. Under periods of stress people
tend to sleep less overall, and also the sleep that they
do get tends to be of a lower quality, both of which can
lead to poorer health outcomes. We know stress also can lead
to a number of physiological changes that over time produce
wear and tear on the body. There are some exciting
new frontiers examining the acceleration of cell aging and
changes to DNA expression under periods of high stress. Now that fact
itself is not exciting, that’s in fact quite worrying if
you experience a lot of stress and you realize that what you’re
actually doing is aging your cells more quickly, but it is
exciting because it may lead to frontiers for how to help
protect us from the long term chronic experience of
stress on the body. We know there’s a number of
things that stress does to the cardiovascular system that over
time with chronic stress can be quite problematic. Stress is associated with
lots of changes to the heart and circulatory systems,
including high blood pressure and enlarged hearts. People with high cardiovascular
reactivity to lab stressors, which we can think of as a
diathesis are particularly vulnerable. What we mean by this is that
there are certain people who under the same
experience of stress, the same level and
intensity of stress, some people tend to have a
high cardiovascular reactivity, meaning they’re heart and
circulatory system respond in a more extreme way to
that same stressor. Those folks are at
greater risk for those sorts of cardiovascular risks
of stress over time, because if you can imagine if
they’re more reactive to say one simple stressor in a lab
environment and they experience lots of chronic
stress over time, it’s sort of like they’ve got
the accelerator pedal down a little too hard on the engine
and putting a lot of miles on that car, or miles on the
heart prematurely and that’s problematic. We know that stress is also
associated with increased levels of cholesterol and inflammatory
substances in the blood, and more and more we’re learning
that cardiovascular disease is really about inflammation,
and that inflammation can be exasperated under
periods of stress. These various changes can
translate into a condition called atherosclerosis, or
plaques and inflammation and hardening of the arteries
that can really develop cardiovascular
problems over time, and lead to strokes and
heart attacks prematurely. We know also that stress can
have impacts on the endocrine system. Stress can influence the body’s
endocrine regulation of fat storage for example,
acceleration fat storage under periods of stress. If you’ve ever noticed in
yourself or heard someone else complain that they seem to add
weight under periods of stress, that may not necessarily be
related to changes in diets, although that may be part of it,
but under periods of stress and chronic stress the body
changes the way it stores energy, it can actually
turn on fat storage. One thing you may hear of,
it’s in the news these days, is a syndrome called
Metabolic Syndrome. It’s a set of risk factors
that include high levels of bad cholesterol,
elevated blood pressure, high levels of insulin, and
fat deposits in the abdomen. Development of the
Metabolic Syndrome is related to experiencing chronic stress. As we saw in the documentary
that was required this week, this syndrome is associated
with stress and social status. So people under stress that are
lower in the social hierarchy have less control, less
influence or power tend to be more at risk for these things. So there you see an environment
interaction with physiology, which is pretty interesting. We also know that people
who express more depression, hostility or anger have greater
risk factors for the development of Metabolic Syndrome under
periods of chronic stress. You may recall that we talked
about the type A personality in a previous lecture, this is one
mechanism by which the type A personality translates
into poorer health outcomes, through the expression
of hostility and anger. There’s some good news though,
stress can also cause the release of oxytocin. Oxytocin is a stress hormone,
it’s a neurohormone that cues what we call tend and
befriend behaviors. These are behaviors that cause
us to seek out social support, to express and feel empathy, and
to bond more closely with people who are close to us under
periods of stress to encourage us to seek out help
under periods of stress. So this lecture summarized a
number of different ways that stress can have
impacts on the body, physiologically as well
as through changing health behaviors that can have long
term impacts on health outcomes.

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