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Stress And Autoimmune Disease
Autoimmune disease and Stress: Is there a link?
Robert
H. Shmerling, MD
Faculty Editor,
Harvard Health Publishing
A
new study has raised the possibility that stress may cause autoimmune
disease, such as lupus or rheumatoid arthritis, because it found
a higher incidence of autoimmune diseases among people who were previously
diagnosed with stress-related disorders.
I
have patients who heard about this research and are saying, “I knew it!”
But before we accept a potential link
between stress and autoimmune disease, let’s look at some details of the study
and consider how we define the terms “autoimmune disease,” “stress,” and “stress-related
disorder.”
What is autoimmune disease?
These
are fascinating and mysterious conditions in which the body’s immune system
“misfires” and attacks its own tissues.
There
are scores of autoimmune diseases out there. Some of the most well-known are rheumatoid arthritis, psoriasis, multiple sclerosis, and type
1 diabetes.
In some cases, a condition is labeled
“autoimmune” based on conventional wisdom or expert consensus rather than hard
science.
And
I’ve seen the term “autoimmune” used loosely to apply to any condition of
unknown cause in which inflammation is present or the immune system appears to
be active.
But
an infection could do the same thing. So perhaps some of these conditions now
considered to be autoimmune will turn out to be chronic infections by an
organism we’ve not yet identified.
What is stress?
A
common definition of “stress” is any experience that causes tension, whether
physical, psychological, or emotional, especially if it sets off the “fight or
flight” response (during which the adrenal gland releases adrenaline,
leading to rapid pulse and breathing, and increased blood pressure).
This
serves us well if chased by a lion. But it’s theorized that persistent stress
(such as worry about finances, mental or physical health, or interpersonal
relationships) could lead to chronic disease such as high blood pressure or
autoimmune disease.
What causes stress for a person is
highly individual. A common example is having to speak in public.
Some
people find it easy to give a speech in front of a crowd; for others, however,
the exact same situation may feel nothing short of dreadful and causes worry
for weeks in advance.
A
stressful experience can also be something quite positive, like getting
married, or walking into a room on your birthday where friends and family are
hiding. Surprise!
What is a stress-related disorder?
There
is a big difference between stress and having a “stress-related disorder,” in
which a particular, well-defined condition or disease develops following a
specific and intensely stressful event.
A
dramatic example is post-traumatic stress disorder (PTSD), in which a serious
physical or psychological injury leads to a host of problems including
distressing, intrusive memories of the traumatic event; memory problems;
apathy; and irritability.
Exploring the connection between stress and autoimmune disease
In
this new study, researchers analyzed more than 100,000 people diagnosed with
stress-related disorders and compared their tendency to develop autoimmune
disease at least one year later with 126,000 of their siblings, and another million
people who did not have stress-related disorders.
The study found that individuals
diagnosed with a stress-related disorder
· were
more likely to be diagnosed with an autoimmune disease (about nine per 1,000
patient-years* who had stress-related disorders, but only about six per 1,000
patient-years among those without stress-related disorders)
· were
more likely to develop multiple autoimmune
diseases
· had
a higher rate of autoimmune disease if younger.
*Patient-years is an expression that
combines how many and for how long people are assessed in a study. If the
frequency of a condition is 9 per 1,000 patient-years, that means 9 people
would develop the disease among ,1000 patients monitored for 1 year, or among
500 patients monitored for 2 years, and so on).
A particularly important observation
was that, for those with PTSD who were being treated with an SSRI (a type of
antidepressant), the increased rate of autoimmune disease was less
dramatic.
While
these observations are intriguing, they don’t tell us why or how a
stress-related disorder might provoke or cause autoimmune disease.
The usual caveats about observational studies
It’s
important to emphasize that a study of this type (called an observational
study) cannot conclude that stress-related disorders actually cause autoimmune disease.
There
could be other explanations for the findings. For example, it is often
impossible to identify a precise date that an autoimmune disease or a
stress-related disorder began.
So,
despite the researchers’ requirement that the autoimmune disease be diagnosed
well after the stress-related disorder, it’s possible that the autoimmune
condition was already present before the
stress-related disorder was diagnosed.
If
that was the case, the stress-related disorder could not have caused the
autoimmune disease.
In addition, it’s possible that
something other than the stress-related disorder was to blame for the higher
rate of autoimmune disease.
For
example, people who have been through severely stressful circumstances may be
more likely to smoke, and smoking has been linked to an increased risk of
certain autoimmune diseases, including rheumatoid arthritis and multiple
sclerosis.
One more point: this study appears to
have included type 2 diabetes among the 41 autoimmune diseases it considered.
Although
this is the most common type of diabetes (accounting for more than 90% of all
cases), it is not considered
an autoimmune disease.
Different
results might have been noted if stricter definitions of autoimmune disease had
been applied.
The mystery of autoimmune illness continues
Whether
stress or stress-related disorders play an important role remains speculative.
Even
more important is the question of whether any particular treatment of these
stress-induced psychological illnesses can prevent autoimmune disease.
I
look forward to a clinical trial that examines this fascinating possibility.
Follow me on Twitter @RobShmerling
Robert H. Shmerling, MD
Faculty
Editor, Harvard Health Publishing
Robert Shmerling, M.D., is associate physician and
clinical chief of rheumatology at Beth Israel Deaconess Medical Center and an
associate professor in medicine at Harvard Medical School. He is an active
teacher in the Internal Medicine Residency Program, serving as the Robinson
Firm Chief. He is also a teacher in the Rheumatology Fellowship Program and has
been a practicing rheumatologist for over 25 years.
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