Understanding The Role Of Stress In Just About Everything

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Understanding The Role Of Stress In Just About Everything

http://www.medicalnewstoday.com/articles/93452.php

A study now reveals that stress causes deterioration in everything

from your gums to your heart and can make you more susceptible to

everything from the common cold to cancer. Thanks to new research

crossing the disciplines of psychology, medicine, neuroscience, and

genetics, the mechanisms underlying the connection are rapidly

becoming understood.

The first clues to the link between stress and health were provided

in the 1930s by Hans Selye, the first scientist to apply the

word " stress " - then simply an engineering term - to the strains

experienced by living organisms in their struggles to adapt and cope

with changing environments.

One of Selye's major discoveries was that the stress hormone

cortisol had a long-term effect on the health of rats.

Cortisol has been considered one of the main culprits in the stress-

illness connection, although it plays a necessary role in helping us

cope with threats. When an animal perceives danger, a system kicks

into gear: A chain reaction of signals releases various hormones -

most notably epinephrine ( " adrenaline " ), norepinephrine, and

cortisol - from the adrenal glands above each kidney.

These hormones boost heart rate, increase respiration, and increase

the availability of glucose (cellular fuel) in the blood, thereby

enabling the famous " fight or flight " reaction.

Because these responses take a lot of energy, cortisol

simultaneously tells other costly physical processes - including

digestion, reproduction, physical growth, and some aspects of the

immune system - to shut or slow down.

When occasions to fight or flee are infrequent and threats pass

quickly, the body's stress thermostat adjusts accordingly: Cortisol

levels return to baseline (it takes 40-60 minutes), the intestines

resume digesting food, the sex organs kick back into gear, and the

immune system resumes fighting infections.

But problems occur when stresses don't let up - or when, for various

reasons, the brain continually perceives stress even if it isn't

really there.

Stress begins with the perception of danger by the brain, and it

appears that continued stress can actually bias the brain to

perceive more danger by altering brain structures such as those

which govern the perception of and response to threat. Prolonged

exposure to cortisol inhibits the growth of new neurons, and can

cause increased growth of the amygdala, the portion of the brain

that controls fear and other emotional responses.

The end result is heightened expectation of and attention to threats

in the environment. Stress hormones also inhibit neuron growth in

parts of the hippocampus, a brain area essential in forming new

memories. In this way, stress results in memory impairments and

impairs the brain's ability to put emotional memories in context.

Think of it this way: Too much stress and you forget not to be

stressed out.

These brain changes are thought by some researchers to be at the

heart of the link between stress and depression - one of stress's

most devastating health consequences - as well as posttraumatic

stress disorder (PTSD).

Although when we think of stressors we might think of big things

like abuse, illness, divorce, grieving, or getting fired, it is now

known that the little things - traffic, workplace politics, noisy

neighbors, a long line at the bank - can add up and have a similar

impact on our well-being and our health.

People who report more minor irritants in their lives also have more

mental and physical health problems than those who encounter fewer

hassles. And recent research shows that PTSD may be the result of

stressors adding up like building blocks, remodeling the plastic

brain in a cumulative rather than a once-and-for-all fashion.

But the best known of stress's health impacts are on the heart.

The idea that stress directly causes coronary heart disease has been

around since the 1950s; although once controversial, the direct

stress-cardiac link is now well-documented by many studies. For

instance, men who faced chronic stresses at work or at home ran a 30

percent higher likelihood of dying over the course of a nine-year

study; in another study, individuals reporting neglect, abuse, or

other stressors in childhood were over three times as likely as

nonstressed individuals to develop heart disease in adulthood.

Adding insult to injury, stress may even have a selfperpetuating

effect. Depression and heart disease, for example, are not only the

results of stress, but also causes of (more) stress. Consequently,

the chronically stressed body can appear less like a thermostat than

like a wailing speaker placed too close to a microphone - a feedback

loop in which the stress response goes out of control, hastening

physical decline with age.

Growing evidence shows that our sensitivity to stress as adults is

already " tuned, " so to speak, in infancy. Specifically, the amount

of stress encountered in early life sensitizes an organism to a

certain level of adversity; high levels of early life stress may

result in hypersensitivity to stress later, as well as to adult

depression.

A history of various stressors such as abuse and neglect in early

life are a common feature of those with chronic depression in

adulthood, for example.

At McGill University in Montreal, J. Meaney and his

colleagues have studied mother and infant rats, using rat maternal

behavior as a model of early life stress and its later ramifications

in humans. The key variable in the world of rat nurturance is

licking and grooming. Offspring of rat mothers who naturally lick

and groom their pups a lot are less easily startled as adults and

show less fear of novel or threatening situations - in other words,

less sensitivity to stress - than offspring of less nurturant

mothers.

The same thing is true of offspring of naturally less nurturant

mothers who are raised (or " cross-fostered " ) by more nurturant ones.

By the same token, low-licking-and-grooming rat mothers are

themselves more fearful than the more nurturant rat moms; but again,

female offspring of those non-nurturant mothers foster-parented by

nurturant mothers show less fear and are themselves more nurturant

when they have pups of their own.

This indicates that the connection between maternal nurturance and

stress responsiveness is not simply genetic, but that fearfulness

and nurturance are transmitted from generation to generation through

maternal behavior.

The vicious cycle of stress hormones biasing us to perceive more

threat and react with an increased stress response might seem like

some kind perverse joke played by nature - or at least a serious

design flaw in the brain. But it makes better sense if we take the

brain out of its modern, urban, " civilized " context.

The stress response is a necessary response to danger.

For animals, including most likely our hominid ancestors, behavioral

transmission of individual differences in stress reactivity from

parents to offspring makes sense as an adaptation to fluctuating

levels of danger in the environment.

Animals raised in chronically adverse conditions (e.g., high

conflict, material deprivation) may expect more of the same in the

near future; so in effect, the maternal treatment of offspring

attunes them to the level of stress they may expect to encounter in

their lives. As such, a response that seems baffling and

counterproductive in a modern, civilized context may make more sense

in the context of our distant evolutionary past.

Even depression has been theorized as playing an adaptive role in

certain contexts.

The inactivity, lack of motivation, loss of interest in pleasurable

activities like sex, and withdrawal from social relationships

experienced by depressed people closely resemble " sickness

behavior " - the energy-saving lethargy activated by the immune

system in response to infection.

In a natural setting, the hopeless attitude of depression may be the

most adaptive for an organism infected with a pathogen: The best

strategy for survival is not to expend energy fruitlessly and become

exposed to predators, but to hunker down, hide from threats, and

direct energy to immune processes where it's needed.

And it turns out that baboons suffer from depression and other

stress-related disorders, just like people do. According to Stanford

neuroendocrinologist Sapolsky, who has studied stress in

baboon troops, it is the relative safety from predators and high

amounts of leisure time enjoyed by some primates - including humans -

that has transformed these useful biological coping mechanisms into

a source of pointless suffering and illness.

Besides heart disease, PTSD, and depression, chronic stress has been

linked to ailments as diverse as intestinal problems, gum disease,

erectile dysfunction, adult-onset diabetes, growth problems, and

even cancer. Chronic rises in stress hormones have been shown to

accelerate the growth of precancerous cells and tumors; they also

lower the body's resistance to HIV and cancer-causing viruses like

human papilloma virus (the precursor to cervical cancer in women).

The great challenge in stress psychology - and the necessary

precursor to developing interventions against stress's harmful

effects - has been understanding the mechanisms by which thoughts

and feelings and other " mental " stuff can affect bodily health.

For many years, it was believed that the main causal link between

stress and disease was the immune suppression that occurs when the

body redirects its energy toward the fight-or-flight response. But

recent research has revealed a far more nuanced picture.

Stress is known to actually enhance one important immune response,

inflammation, and increasingly this is being seen as the go-between

in various stress-related diseases.

Ordinarily, inflammation is how the healthy body deals with damaged

tissue: Cells at the site of infections or injuries produce

signaling chemicals called cytokines, which in turn attract other

immune cells to the site to help repair it. Cytokines also travel to

the brain and are responsible for initiating sickness behavior.

Overactive cytokine production has been found to put individuals at

greater risk for a variety of aging-related illnesses.

Cytokines may be an important mediator in the relationship between

stress and heart disease. When the arteries feeding the heart are

damaged, cytokines induce more blood flow, and thus more white blood

cells, to the site. White blood cells accumulate in vessel walls

and, over time, become engorged with cholesterol, becoming plaques;

these may later become destabilized and rupture, causing heart

attacks.

Cytokine action also has been implicated in the link between stress

and depression. People suffering from clinical depression have shown

40-50 percent higher concentrations of certain inflammatory

cytokines. And about 50 percent of cancer patients whose immune

responses are artificially boosted through the administration of

cytokines show depressive symptoms.

The close connection between inflammation and both depression and

heart disease has led some researchers to theorize that inflammation

may be what mediates the two-way street between these two

conditions: Depression can lead to heart disease, but heart disease

also often leads to depression.

Sleep may be part of this puzzle too, as disturbed sleep, which

often goes with anxiety and depression, increases levels of

proinflammatory cytokines in the body.

Not everyone responds the same way to stress. Personality traits

like negativity, pessimism, and neuroticism are known to be risk

factors for stress-related disease, as are anger and hostility.

In the late 1950s, Friedman and Rosenman identified a major link

between stress and health with their research on the " Type A "

personality: a person who is highly competitive, aggressive, and

impatient. This personality was found to be a strong predictor of

heart disease, and later research clarified the picture: The salient

factors in the relationship between the Type A personality and

health are mainly anger, hostility, and a socially dominant

personality style (for example, tending to interrupt other people

while they are talking).

When negative emotions like anger are chronic, it is as if the body

is in a constant state of fight or flight.

There is now evidence that another trait associated with success-

striving in the modern world - persistence - may also lead to health

problems in some circumstances. When goals are not readily

attainable, the inability to detach from them may produce

frustration, exhaustion, rumination on failures, and lack of sleep.

These in turn activate harmful inflammatory responses that can lead

to illness and lowered immunity.

Studies also have shown that optimistic people have lower incidence

of heart disease, better prognosis after heart surgery, and longer

life.

The effects of a positive attitude on immunity were shown in a study

by Sheldon Cohen, Carnegie Mellon University, and his colleagues, in

which individuals were exposed to a cold virus in a laboratory

setting and watched over six days. Those with a positive emotional

style were less likely to develop colds than were individuals with

low levels of positive affect. Positive affect was also found to be

correlated with reduced symptom severity and reduced pain.

Personality and environmental factors are not the whole story when

it comes to stress.

The next frontier of stress research is the rapidly growing field of

behavioral genetics. Modeling the interaction of genetic and

environmental influences is no longer a matter of weighing the

relative input of nature and nurture. The two intertwine in subtle

and complicated ways, with environments affecting gene expression,

and vice versa, throughout life. Thus, the current watchword

is " stress-diathesis " models, in which environmental stressors have

varying impact on individuals due to preexisting inherited

vulnerabilities.

One major advance in this area was the discovery by Avshalom Caspi,

University of Wisconsin, and his colleagues of a link between stress

sensitivity and a particular gene called 5HTTLPR. Findings suggest

certain genetic makeup seems to increase the risk for a serious

illness through the mechanism of increased sensitivity to stressful

occurrences.

Fox, University of land, and his colleagues subsequently

reported that children with two short alleles of the 5HTTLPR gene,

whose mothers also reported receiving low social support, were more

likely to show behavioral inhibition (fearfulness and a tendency to

withdraw) at age 7. Those receiving high support did not show the

tendency, and those with the long alleles but receiving low support

also appeared " protected " by their genetic makeup.

Genetic predisposition to stress sensitivity may in some cases

become a self-fulfilling cycle. Fox and colleagues found that some

very behaviorally inhibited children were regarded by their mothers

as hard to soothe and received less care and sensitivity as a

result; this in turn tuned up the child's sensitivity to stress. In

the model Fox and colleagues propose, genetically influenced

temperament in early childhood influences the quality of caregiving

children receive, which in turn shapes a child's attention bias to

threat.

But look on the bright side: The newly refined science of stress

could lead to new drug therapies that can control stress or inhibit

its effects on health. Also, depression and anxiety are not only

results of stress, but also causes, and existing therapeutic and

medical treatments for these conditions can help change how people

perceive threats, put their life challenges in context, and cut

stressors down to manageable size. The cycle doesn't have to be

vicious, in other words.

What's more, the confirmation that the mind directly affects the

body can work as much in our favor as it does to our detriment, as

the personality-and-stress research above indicates.

As Carol Dweck, Stanford University, has argued, personality is

mutable. In theory, if our outlooks and beliefs about ourselves can

be changed, so can our vulnerability to life's slings and arrows.

Relaxation techniques such as meditation and yoga, for example, have

been confirmed to quell stress demons.

Even if you are a determined workaholic glued to your cell phone or

a fearful and angry urban neurotic, stress-reduction methods are

readily available to cope with stress in the short term and even

alter perceptions of stressors in the long term. The bottom line:

Stress is not inevitable.

Current Research on Stress:

At the University of Chicago, APS President Cacioppo and Louise

Hawkley have studied the health effects of social isolation, an

increasingly common malady in the modern world. Among their findings

are that lonely older adults show more arterial stiffening and

higher blood pressure than their nonlonely counterparts and that the

association between loneliness and blood pressure increases with

age.

In middle-aged and older adults (but not young adults), loneliness

is associated with higher levels of epinephrine in the blood, and

lonely people of all ages show elevated levels of cortisol. By

desensitizing the mechanism whereby cortisol turns off more cortisol

production, the social isolation frequently experienced by older

adults may hasten physical decline. Lonely individuals of all ages

also have poorer sleep than nonlonely people and therefore get less

of sleep's essential restorative benefits.

Humans and other social animals particularly seek the company of

others when facing threats - both for safety and for social support.

The general affiliative response - what , UCLA, has

called " tending and befriending. " Oxytocin rises during times of

separation or disrupted social relations. Just as the

familiar " adrenaline rush " of epinephrine induces the familiar fight-

or-flight reaction, it is oxytocin that causes us to desire company

and social togetherness.

It may be especially important in females, reflecting their

different reproductive and survival priorities from those of males -

i.e., caregiving (tending offspring) and lessening social tensions

through friendly overtures (befriending).