HOW STRESS AFFECTS HEALTH:Stress, Behavior and Illness, Psychoneuroimmunology

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Health Psychology PSY408

Lesson 19

HOW STRESS AFFECTS HEALTH

Researchers conducted an interesting experiment: they gave subjects nasal drops that contained a common

cold" virus or a placebo solution and then quarantined them to check for infection and cold symptoms.

Before the nasal drops were administered, the subjects had filled out questionnaires to assess their stress. Of

these subjects, 47% of those with high stress and 27% of those with low stress developed colds.

Other studies have produced two related findings. First, people who are under chronic, severe stress are

especially vulnerable to infection. Second, people who show high reactivity to stress are at greater risk to

respiratory infections when stressed than less reactive people. What is it about stress that leads to illness?

The causal sequence between stress and illness can involve either of two routes: (1) a direct route, resulting

from the changes stress produces in the body's physiology, or (2) an indirect route, affecting health through

the person's behavior. Let's look first at the behavioral route.

Stress, Behavior and Illness

Stress can affect behavior, which, in turn, can lead to illness or worsen art existing condition. We can see the

behavioral links between stress and Illness In many stressful situations, such as when a family undergoes a

divorce. In many cases during the first year following the separation, the parent who has the children is less

available and responsive to them than she or he was before--a situation described as "diminished

parenting". Behavioral changes during stressful times often make conditions for all family members less

healthful, with haphazard meals, less regular bedtimes, delays in getting medical attention, and failures to

follow physician's recommendations, for example.

Research has shown that people who experience high levels of stress tend to perform behaviors that

increase their chances of becoming ill or injured. For instance, they consume more alcohol, cigarettes, and

coffee than people who experience less stress. Consumption of these substances has been associated with

the development of various illnesses. In addition, behavioral factors, such as alcohol use and carelessness,

probably play a role in the relatively high accident rates of people under stress. Studies have found that

children and adults who experience high levels of stress are more likely to suffer accidental injuries at home,

in sports activities, on the job, and while driving a car than individuals under less stress.

Stress, Physiology and Illness

Stress produces many physiological changes in the body that can affect health, especially when stress is

chronic and severe. In one of our previous lectures, we discussed the concept of allostatic load in which the

strain involved in adapting repeatedly to intense stressors produces wear and tear on body systems that

accumulate over time and lead to illness. Clear connections have been found between illness and the degree

of reactivity people show in their cardiovascular, endocrine, and immune systems when stressed.

Cardiovascular System Reactivity and Illness

Cardiovascular reactivity includes any physiological change that occurs in the heart, blood vessels, and blood

in response to stressors.

Research has demonstrated links between chronically high cardiovascular reactivity and the development of

CHD and hypertension. For example, high levels of job stress are associated with high blood pressure and

abnormally enlarged hearts, and people's laboratory reactivity to stress in early adulthood is associated with

their later development of high blood pressure. The heightened blood pressure reactivity that people display

in laboratory tests appears to reflect their reactivity in daily life.

Health Psychology PSY408

Stress produces several cardiovascular changes that relate to the development of CHD. For Instance, the

blood of people who are under stress contains high concentrations of activated platelets and unfavorable

levels of lipids, such as cholesterol. These changes in blood composition tend to promote atherosclerosis--

the growth of plaques (fatty patches) on artery walls.

As these plaques build up, they narrow an1 harden the arteries, thereby increasing blood pressure and the

likelihood of a heart attack or stroke. Prospective studies have found that people who display high

cardiovascular reactivity to stressors show faster progression of atherosclerosis than those with lower

reactivity, especially if they experience chronic, severe stress in their lives.

Endocrine System Reactivity and Illness

Part of reactivity involves activation of the hypothalamus--pituitary--adrenal axis, which releases

endocrine hormones--particularly catecholamines and corticosteroids--during stress. The increased

endocrine reactivity that people display in these tests appears to reflect their reactivity in daily life. One way

in which high levels of these hormones can lead to illness involves their effects on the cardiovascular

system. For example, an intense episode of stress with extremely high levels, of these hormones can cause

the heart to beat inconsistently and may lead to sudden death. In addition, chronically high levels of

catecholamines and corticosteroids appear to increase atherosclerosis.

Stephen Manuck and his colleagues have demonstrated this link between stress and atherosclerosis in

research with monkeys. In one study, some of the subjects were relocated periodically to different living

groups, thereby requiring stressful social and psychological adjustments to retain their dominant social

status: the remaining subjects stayed in stable groups. Regardless of whether the monkeys' diets had high or

low levels of cholesterol, the stressed subjects who had to retain their dominant status developed greater

atherosclerosis than the subjects in the low stress condition. This effect of stress is probably very similar in

humans. Disruptions of soldiers' social status in boot camp affect endocrine reactivity. And as we saw

earlier, people with chronically high stress are more likely to develop atherosclerosis than those with less

stress. But social support may help: people with high levels of social support tend to exhibit lower

endocrine reactivity than people with less support.

Immune System Reactivity and Illness

The release of catecholamines and corticosteroids during arousal affects health in another way: some of

these hormones impair the functioning of the immune system. For example, increases in cortisol and

epinephrine are associated with decreased activity of T cells and B cells against antigens. This decrease in

lymphocyte activity appears to be important in the development and progression of a variety of infectious

diseases and cancer. Among women diagnosed with breast cancer, those with high levels of killer-T-cell

activity exhibit less spread of the cancer to surrounding tissue than those with low levels of lymphocyte

activity.

Immune processes also protect the body against cancers that result from excessive exposure to harmful

chemical or physical agents called carcinogens, which include radiation (nuclear, X, and ultraviolet types),

tobacco tars, and asbestos (AMA, 1989). Carcinogens can damage the DNA in body cells, which may then

develop into mutant cells and spread.

When mutant cells develop, the immune system attacks them with killer T cells. Actually, the body begins to

defend itself against cancer even before a cell mutates by using enzymes to destroy chemical carcinogens or

to repair damaged DNA. Research has shown that high levels of stress, however, reduce the production of

these enzymes and the repair of damaged DNA.

Psychoneuroimmunology

We have seen earlier that psychological and biological systems are interrelated-- as one system changes, the

others are often affected. The recognition of this interdependence and its connection to health and illness

Health Psychology PSY408

led researchers to form a new field of study called psychoneuroimmunology. This field focuses on the

relationships between psychosocial processes and the activities of the nervous, endocrine, and immune

systems. These systems form a feed back loop: the nervous and endocrine systems send chemical messages

in the form of neurotransmitters and hormones that increase or decrease immune function, and cells of the

immune system produce chemicals, such as ACTH, that feed information back to the brain. The brain

appears to serve as a control center to maintain a balance in immune function, since too little Immune

activity leaves the individual open to infection and too much activity may produce autoimmune diseases.

Emotions and Immune Function

People's emotions--both positive and negative--play a critical role in the balance of Immune functions.

Research has shown that pessimism, depression, and Stress from major and minor events are related to

impaired Immune function. For example, studies have compared immune variables of caregiver spouses of

Alzheimer's disease patients with matched control subjects. One study found that the caregivers had lower

immune function and reported more days of illness over the course of about a year. Other studies have

confirmed caregivers' reduced immune function and found that men's immune systems are more vulnerable

than women's to care-giving stress and that care-giving does not seem to impair immune responses when

new brief stressors occur.

Positive emotions can also affect immune function, giving it a boost. In the study by Arthur Stone and his

coworkers, adult men kept daily logs of positive and negative events and gave saliva samples for analyses of

antibody content. Negative events were associated with reduced antibodies only for the day the events

occurred, but positive events enhanced antibody content for the day of occurrence and the next two.

Some stressful situations start with a crisis, and the ensuing emotional states tend to continue and suppress

immune processes over an extended period of time. This was demonstrated with healthy elderly individuals

who were taking part in a longitudinal study of the aging process. The subjects were asked to contact the

researchers as soon as they were able if they experienced any major crisis, such as the diagnosis of a serious

illness in or the death of a spouse or child. Fifteen subjects did so. A month after the crisis, and again

several months later, the researchers assessed the subjects' cortisol and lymphocyte blood concentrations,

recent diets, weights, and psychological distress.

Because the subjects were already participating in the longitudinal study, comparable data were available

from a time prior to the crisis. Analysis of these data revealed that lymphocyte concentrations, caloric

intake, and body weight decreased, and cortisol concentrations and psychological distress increased soon

after the crisis. By the time of the last assessment several months later, however, all of these measures had

returned almost to the pre-crisis levels.

When people are reacting to short-term, minor events, such as doing difficult math problems under time

pressure, changes in the number and activity of immune cells occur for fairly short periods of time--

minutes or hours, and some measures even improve. The degree of change seems to vary with the event's

intensity, duration, and type--such as whether the event is interpersonal or nonsocial. Long-lasting and

intense interpersonal events seem to produce especially large immune reductions. Of course, immune

system reactivity varies from one person to the next, but a person's degree of response to a type of event

seems to be much the same when tested weeks apart. This suggests that an individual's reaction to specific

stressors is fairly stable over time.

Psychosocial Modifiers of Immune System Reactivity

We saw earlier that psychosocial factors in people's lives may modify the stress they experience. Such

factors seem to affect immune system responses, too. For instance, social support affects the immune

function of people under tong-term, intense stress. People who have strong social support have stronger

immune systems and smaller immune impairments in response to stress than others with less support.

Health Psychology PSY408

Research has also demonstrated that physical exercise and psychotherapy to reduce stress can enhance

immune function in people infected with the AIDS virus.

A related psychosocial modifier involves describing one's feelings about stressful events. An experiment

with college student subjects examined the effect of expressing such feelings on blood concentrations of

antibodies against the Epstein-Barr virus, a widespread virus that causes mononucleosis in many of those

who are infected. The students were randomly assigned to three conditions that met in three weekly 20-

minute sessions when they either described verbally or in-writing a highly stressful event they had

experienced or wrote about a trivial (non-stress-related) topic, such as the contents of their bedrooms.

The subjects in each condition had the same level of immune control against the virus before the start of

the study. But analysis of blood samples taken a week after the last session revealed that immune control

improved substantially in the verbal condition, moderately in the written condition, and declined slightly in

the control (trivial topic) condition. The influence of optimism on immune function appears to depend on

whether the stress is short- term or chronic.

Lifestyles and Immune Function

Do people's lifestyles affect the functioning of their Immune systems? Some evidence suggests that they do.

People with generally healthful lifestyles-- including exercising, getting enough sleep, eating balanced meals,

and not smoking--show stronger immune functioning than those with less healthful lifestyles. Other

studies have found that sleeping poorly impairs immune function the next day and people who smoke are

more susceptible to catching colds.

In summary, stress affects health in two ways. First, stress can affect health-related behaviors, such as

alcohol and cigarette use. Second, it produces changes in the body's physical systems, as when the endocrine

system releases catecholamines and corticosteroids, which can cause damage to the heart and blood vessels

and impair immune system functioning. The physical effects of intense stress can even lead to sudden

death. Psychoneuroimmunology is a new field of study that focuses on how psychosocial processes and the

nervous, endocrine, and immune systems are interrelated.

Stress also plays a role in many psychophysiological disorders, such as ulcers, asthma, tension-type and

migraine headache, rheumatoid arthritis, and several skin disorders. In addition, stress is implicated in the

development of hypertension, CHD, and cancer. We will study these psychophysiological disorders in detail

in our later coming lectures.

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