New Study on Personality and Placebos Could Improve Drug Testing
Personality traits might do more than help you win a popularity
contest. According to new University of Michigan-led neuroscience
research, co-authored by University of Maryland (UM) School of Dentistry Dean Christian S. Stohler, DMD, DrMedDent,
such traits also might make you more likely to get pain relief from a
placebo - a fake medicine.
"This work fits into the bigger picture regarding the degree to which
our individual response to a stress factor is imprinted in our
personality." The release of stress-relieving neurotransmitters,
such as opiates in our brain, triggered by the application of the
stress explain much of the individual variance in the response to
treatment," says Stohler.
In short, if you're more of an angry, hostile type, they find, a
placebo won't do much for you.
For the first time, the new findings link specific, established
personality traits with an individual's susceptibility to the placebo
effect from a sham medicine for pain. The researchers showed a
significant link between certain personality traits and how much relief
people said they felt when given the placebo - as well as the level of
a specific chemical that their brains released.
The work, published online today in the journal Neuropsychopharmacology, was done
by a team of researchers at the University of Michigan, the University
of North Carolina, and the University of Maryland.
The results build on nearly a decade's worth of work on the placebo
effect by the team led by Jon-Kar Zubieta, MD, PhD, the Phil Jenkins
Professor of Depression in the University of Michigan Department of
Psychiatry. Stohler is a nationally recognized contributor to pain
research and often collaborates with colleagues at the University of
Michigan, where he served as the chair of the Department of Biologic
and Materials Sciences before coming to the UM School of Dentistry as
dean in January 2003.
The findings show that about one-quarter of placebo response was
explained by the personality traits of resiliency, straightforwardness,
altruism, or anger/hostility, as measured on standardized tests. Other
personality traits didn't appear to be linked to placebo response. The
new results come from a few dozen healthy volunteers, so the experiment
must be repeated in larger, more diverse groups to be confirmed.
If confirmed, the findings could help researchers who study new drugs
and other treatments - a field where placebo responses can muddy the
results and make it unclear whether the real therapy is working.
Perhaps someday researchers will be able to adjust their results to
account for the individual placebo responses of volunteers in their
clinical trials. Zubieta notes that the new findings came from a study
involving pain, but that they also may apply to how personality
influences a person's response to other stress-inducing circumstances.
"We started this study not just looking at measures that might seem
more obviously related to placebo responses, such as maybe impulsivity,
or reward-seeking, but explored potential associations broadly without
a particular hypothesis," he explains. "We ended up finding that their
greatest influence came from a series of factors related to individual
resiliency, the capacity to withstand and overcome stressors and
difficult situations. People with those factors had the greatest
ability to take environmental information - the placebo - and convert
it to a change in biology."
He notes that the findings may even have implications for the
doctor-patient relationship, for instance, patients who have certain
personality traits and placebo-response tendencies may also be more
likely to partner with their doctors on their care, and discuss frankly
any concerns they have about their response to treatment.
The researchers conducted the study among nearly 50 healthy volunteers,
both male and female, between the ages of 19 and 38. They gave each
person a battery of standard psychological tests that help identify the
strongest personality traits an individual has, and then had them lie
down in a brain scanner called a positron emission tomography or PET
They told the volunteers that they were going to experience pain from
saltwater injected into their jaw muscle, and that a painkiller,
actually, a placebo, would be injected at certain times. They asked
patients to rate how much relief they expected to get before the experiment began. Then, during the 20-minute period when volunteers
received saltwater and/or 'painkiller,' they asked them repeatedly to
say how effective they thought the painkiller was.
Meanwhile, the PET scanner made images of volunteers' brains, allowing
the researchers to see how much of the natural painkillers, called
endogenous opioids, were released in certain areas of each person's
brain under painful or 'painkiller' conditions. They also drew blood
from some of the patients during the experiment, and measured levels of
a stress-induced chemical called cortisol.
After the tests, the researchers performed sophisticated statistical
analysis to determine how personality traits influenced pain ratings,
brain chemical response, and cortisol levels. Although the cortisol
levels did not seem to be influenced by personality traits and the
placebo effect, the endogenous opioid activation elicited by the
placebo, as well as patient-rated pain intensity levels, were.
The research was supported by grants from the National Institutes of
|Posting Date: 11/15/2012
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