eginning in the 1930s, a
McGill University fellow (later
University of Montreal profes-
sor) named Hans Selye pub-
lished a series of academic
papers on stress and what he
called the “general adapta-
tion syndrome” of living organisms. Selye’s big
idea, groundbreaking at the time, was that the
human body’s “basic reaction” to any threat—be it
physical or psychological—is more or less the same
regardless of the threat’s source. Whether a per-
son is being stalked by a mountain lion or by con-
cern for a sick loved one, the same internal defense
mechanisms kick into gear. These mechanisms in-
volve “every vital organ and function,” Selye wrote,
and any problems or “derailments” that arise in this
process could cause or contribute to potentially
grave health concerns.
Selye [see page 16] was a
clear-eyed scientist, and he
acknowledged that it would
likely take generations for re-
searchers to firmly grasp the in-
tricacies and consequences of
the human body’s response to
stress. He wasn’t far off. Flash-
forward to the present, and the
latest research on stress bears
out many of his theories.
“One of the biggest discover-
ies of the last 20 years is that stress can influence
how the immune system operates and that the in-
flammation that results from stress plays a role in
many different diseases and disorders,” says George
Slavich, director of the Laboratory for Stress Assess-
ment and Research at UCLA.
Inflammation is the immune system’s primary
weapon against infection or injury. During periods
of inflammation, the blood is infused with various
enzymes and proteins that, in an attempt to heal
wounds or rebuff invaders, can cause heat, pain or
swelling. While short periods of stress and the in-
flammation it unleashes can exacerbate some pre-
existing medical conditions, none of this seems to
be harmful for healthy adults. In fact, a little stress
can help people stay sharp and respond to a press-
ing challenge. But if stress lingers for long periods,
its effects can have wide-ranging and sometimes
disastrous consequences for a person’s mental and
physical health. From the function of the brain and
heart to the activity of individual cells, there’s vir-
tually no part of the body that stress doesn’t touch.
Experts today are still revealing and refining the
many roles stress plays in disease and dysfunction.
But what they’ve learned to date can help people of
all ages lead healthier, happier lives.STRESS, DEFINED
stress, in a nutshell, is anything a person
perceives to be a threat. The word “perceives” is
important here because threat perception can vary
widely from one person to the next, and it deter-
mines the intensity and duration of the body’s
many stress-related reactions. “There can be a big
difference between what you perceive and what
threat actually exists, but the difference is arbitrary
when it comes to the body’s response,” says Chris-
topher Fagundes, an associate
professor of psychology at Rice
University in Texas whose re-
search into stress and disease
is funded by the National In-
stitutes of Health. “Your body
reacts to your perception of a
threat—not to the reality.”
A simple way to illustrate
this is to imagine two people
locked in a room with a spi-
der. One of the people has a
terrible fear of spiders, while
the other does not. The immediate threat to both
of them is exactly the same. But their perceptions
of that threat and their bodies’ reactions to it are
quite different.
Perception is also important because, unlike
pretty much every other living thing on Earth, peo-
ple have the ability to predict a threat and prepare
ahead of time for the harm it may inflict. “It turns
out that the body starts to mount an immune re-
sponse not just in response to an injury but in an-
ticipation of an injury,” Slavich says. “And humans
have the ability to manifest danger in their minds
even when it’s not present.”
This is where anxiety comes into play. Although
the terms “stress” and “anxiety” are often used in-
terchangeably, they’re not quite the same. Stress is
an external threat—such as a mountain lion stand-
ing in your path or a raging fire that forces you to
flee your home. Stress is also the body’s reactionTHE SCIENCE OF STRESS DEFINING STRESS
Stress is anything
we perceive to
be a threat—but
perception can vary
widely from person
to person.