University of Colorado at Boulder
You don't think you're hungry, then a friend mentions how hungry he is or you smell some freshly baked pizza and whoaaa, you suddenly feel really hungry.
Or, you've had surgery and need a bit of morphine for pain. As soon as you hit that button you feel relief even though the medicine hasn't even hit your bloodstream.
These are two examples of the oft-studied placebo effect that
demonstrate the amazing and still somewhat confounding powers of the human
brain.
Now, CU-Boulder graduate student Scott Schafer, who works in Associate Professor Tor Wager's Cognitive and Affective Neuroscience Lab in the Department of Psychology and Neuroscience, has conducted an intriguing piece of research to advance knowledge about how and when the placebo effect works -- or doesn't.
In short, he discovered that the placebo effect still works even
if research participants know the treatment they are receiving to ease pain has
no medical value whatsoever.
Here's the hitch: The subjects need ample time -- in this case
four sessions -- to be conditioned to believe the placebo works. Then, even
after it is revealed that the treatment is fake, they continue to get pain
relief. When participants are told the truth about the treatment after only one
session, they don't show a continued placebo effect.
The findings suggest that reinforcing treatment cues with
positive outcomes can create placebo effects that are independent of reported
expectations for pain relief.
Wager, the senior author of the study, explains:
"We're still learning a lot about the critical ingredients of placebo
effects. What we think now is that they require both belief in the power of the
treatment and experiences that are consistent with those beliefs. Those
experiences make the brain learn to respond to the treatment as a real event.
After the learning has occurred, your brain can still respond to the placebo
even if you no longer believe in it."
Schafer, Wager, and co-author Luana Colloca, of the University
of Maryland Baltimore, had their paper "Conditioned Placebo Analgesia
Persists When Subjects Know They Are Receiving a Placebo" published in the
May issue of The Journal of
Pain, a peer-reviewed scientific publication.
Schafer, 33, said his advisor helped him refine his area of
research around placebos.
"My general interests are specifically in how we learn to
predict the environment around us," he said. "Digging into how
placebos occur and when and why they arise is really interesting."
To conduct the research, Schafer and Colloca applied a ceramic
heating element to research subjects' forearms. They applied enough heat to
induce strong pain sensations, though not enough to burn the skin.
Interestingly, Schafer ended up having to turn some potential
test subjects away because of a higher than normal pain tolerance on their
forearms. Turns out, some of these people were food servers accustomed to
carrying hot plates of food to hungry diners.
After applying heat of up to 117.5 degrees Fahrenheit to the
research subjects who passed the initial screening, Schafer applied what the
subject thought was an analgesic gel on the affected skin then -- unbeknownst
to the research subject -- turned down the temperature. To aid in the charade,
the subject was asked to read drug forms and indicate whether they had liver
problems or were taking other medications prior to receiving the treatment..
In fact, the treatment was Vaseline with blue food coloring in
an official-looking pharmaceutical container.
"They believed the treatment was effective in relieving pain,"
Schafer said. "After this process, they had acquired the placebo effect.
We tested them with and without the treatment on medium intensity. They
reported less pain with the placebo."
For Schafer, the research findings could open doors to new ways
to treat drug addiction or aid in pain management for children or adults who
have undergone surgery and are taking strong and potentially addictive
painkillers.
"If a child has experience with a drug working, you could
wean them off the drug, or switch that drug a placebo, and have them continue
taking it," Schafer said.
Schafer believes the brain plays a key role in subjects for whom
the placebo gel worked, and that more research is warranted.
"We know placebos induce the release of pain-relieving
substances in the brain, but we don't yet know whether this
expectation-independent placebo effect is using the same or different
systems," Schafer said.