Why HIV Kills More Shy People
Dwayne Hunter
Betterhumans Staff
Monday,
December 15, 2003, 4:31:26 PM CT
Personality
influences the immune system's ability to fight off diseases
such as AIDS, and now researchers have found why shy people
are at greater risk.
The
researchers, from the University
of California, Los Angeles, have identified a mechanism
linking the way people react to stress
with their ability to resist infection.
"Since
ancient Greece, physicians have noticed that persons with a
'melancholic temperament' are more vulnerable to viral
infections," says Steve Cole, principal investigator for
the research, assistant professor of hematology-oncology at
the David Geffen School of Medicine at UCLA and a member of
the UCLA AIDS Institute.
Ill
introverts
Cole
and colleagues identified the immune mechanism that makes shy
people more susceptible to infection than outgoing people.
"During
the AIDS epidemic, researchers found that introverted people
got sick and died sooner than extroverted people," says
Bruce Naliboff, coauthor of the research and a clinical
professor at the UCLA Neuropsychiatric Institute. "Our
study pinpoints the biological mechanism that connects
personality and disease."
To
identify the mechanism, the researchers examined a group of 54
HIV infected
men, all still in the early stages of the disease and in good
health, to determine the effects of stress on viral
replication.
The
researchers administered a series of stress tests in the lab
to measure the response of the men's autonomic system.
They
measured response to stimuli such as an unexpected beeping
sound, checking heart rate, skin moisture and dilation of
blood vessels, which contract during stress to reroute blood
to the legs for fighting or fleeing.
"Shy
persons didn't adapt to the beeps as fast as other
people," explained Cole. "Their heightened nervous
system response indicated that the sound was more irritating
to them."
In
the next test, the men were asked to perform physical
exercises such as deep breathing or standing from a seated
position—both of which require the nervous system to quickly
adapt.
The
last test required the men to perform rapid mental arithmetic
while the scientists would reply curtly to a wrong answer and
require subjects to start over.
Stressed
sicker
The
researchers ranked participants by totaling their nervous
system reactions during physical and mental tests to gauge
their "stress personality."
They
measured the link between nervous system activity and HIV
progression by monitoring HIV viral load and T
cells over a 12- to 18-month period.
"We
found a strong linear relationship between personality and HIV
replication rate in the body," says Cole. "Shy
people with high stress responses possessed higher viral
loads."
The
correlation was so profound, the researchers were surprised to
find, that antiretroviral drugs barely had an impact in shy
patients. HIV replicated 10 to 100 times as fast in infected
introverts compared to others taking the drugs.
"Our
findings suggest that high nervous system activity helps the
virus continue replicating," Cole says. "Patients
with high-stress personalities continued to lose T
cells—even on the best drug therapy available. Stress
sabotages their battle against this lethal disease."
Psychological
risk factors for HIV pathogenesis: mediation by the autonomic
nervous system
Steve W. Cole, Margaret E. Kemeny , John L. Fahey, Jerome A. Zack and
Bruce D. Naliboff
a Department of Medicine, University of California,
Los Angeles, Los Angeles, California, USA (SWC, JAZ)
b Departments of Microbiology, Immunology, and
Molecular Genetics, University of California, Los Angeles, Los
Angeles, California, USA (JLF, JAZ)
c Department of Psychiatry and Biobehavioral
Sciences (BDN), University of California, Los Angeles, Los
Angeles, California, USA
d AIDS Institute (SWC, JLF, JAZ), University of
California, Los Angeles, Los Angeles, California, USA
e Department of Psychiatry (MEK), University of
California, San Francisco, California, USA
f Department of Veterans Affairs Greater Los
Angeles Area Healthcare System (BDN), Los Angeles, California,
USA
Received 8 July 2002; revised 24 October 2002;
accepted 1 November 2002. ; Available online 11 April
2003.
Abstract
Background
Epidemiologic
studies have identified psychological risk factors for
specific physical diseases, but the biological mechanisms
mediating these relationships remain poorly defined.
Methods
Social inhibition
and autonomic nervous system (ANS) activity were assessed on
multiple occasions in 54 gay men with asymptomatic human
immunodeficiency virus (HIV) infection. Following baseline ANS
assessment, plasma HIV-1 viral load and CD4+ T cell levels
were monitored for 12–18 months to assess relationships
between ANS activity and HIV pathogenesis.
Results
We confirmed the
previously reported relationship between socially inhibited
temperament and vulnerability to viral pathology. Plasma viral
load set-point was elevated eight-fold in socially inhibited
individuals, and these individuals showed poorer virologic and
immunologic response to initiation of highly active
antiretroviral therapy (HAART). Effects were independent of
duration of infection, HAART regimen, demographic
characteristics, and health-relevant behavior.
Neurophysiologic assessments documented elevated ANS activity
in socially inhibited individuals, and mediational analyses
showed that such differences could account for 64%–92% of
the covariance between social inhibition and virologic
parameters.
Conclusions
These data provide
the first clinical evidence that differential neural activity
mediates relationships between psychological risk factors and
infectious disease pathogenesis. Such findings also suggest
novel targets for adjunctive therapy in long-term control of
HIV-1 disease.
Author
Keywords: Temperament; autonomic nervous system;
viral pathogenesis; human immunodeficiency virus;
psychoneuroimmunology
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