Invitation to Psychology

464 ChapTER 13 Emotion, Stress, and Health

substances (antigens), such as flu viruses, bacteria,

and tumor cells, and then destroy or deactivate

them. The immune system deploys different kinds

of white blood cells as weapons, depending on

the nature of the enemy. Natural killer cells are

important in tumor detection and rejection, and

are involved in protection against the spread of

cancer cells and viruses. Helper T cells enhance

and regulate the immune response; they are the

primary target of the HIV virus that causes AIDS.

Chemicals produced by the immune cells are sent

to the brain, and the brain in turn sends chemi­

cal signals to stimulate or restrain the immune

system. Anything that disrupts this communica­

tion loop, whether drugs, surgery, or chronic

stress, can weaken or suppress the immune system

(Segerstrom & Miller, 2004).

Some PNI researchers have gotten right

down to the level of cell damage to see how stress

can lead to illness, aging, and even premature

death. At the end of every chromosome is a pro­

tein complex called a telomere that, in essence, tells

the cell how long it has to live. Every time a cell

divides, enzymes whittle away a tiny piece of the

telomere; when it is reduced to almost nothing,

the cell stops dividing and dies. Chronic stress,

especially if it begins in childhood, appears to

shorten the telomeres (Epel, 2009).

Stress and the Mind LO 13.12, LO 13.13

Before you try to persuade your instructors that

the stress of constant studying is bad for your

health, consider this mystery: The large majority

of individuals who are living with stressors, even

serious ones such as loss of a job or the chronic

these interwoven factors. The “psycho” part stands

for psychological processes such as emotions and

perceptions; “neuro” for the nervous and endocrine

systems; and “immunology” for the immune sys­

tem, which enables the body to combat disease and

infection.

PNI researchers are especially interested in

the white blood cells of the immune system, which

are designed to recognize foreign or harmful

Less than 1 month

Chronic stress by duration

Routine stress

Chronic stress by type

(at least a month)

Relative risk of a cold

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Interpersonal

1 to 6 months

6 months to 2 years

More than 2 years

Work (unemployment

or underemployment)

FIgURE 13.4 Stress and the Common Cold

Chronic stress lasting a month or more boosts the risk of catching a cold. The risk is

increased among people undergoing problems with their friends or loved ones; it is

highest among people who are out of work (Cohen et al., 1998).

The immune system consists of fighter cells that look

more fantastical than any alien creature Hollywood

could design. This one is about to engulf and destroy a

cigarette-shaped parasite that causes a tropical disease.