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How do fake drugs called placebos kill some patients' pain? Until now, nobody knew. As this ScienCentral News video explains, brain scans have let scientists observe for the first time how the placebo effect activates the brain's own painkillers -- which could lead to better pain management.
It's All In Your Mind?
Most of us assume that a hospital injection must have medicine in it to do any good, but University of Michigan psychiatrist Jon-Kar Zubieta proved that assumption wrong. He found that if he told patients that an injection contained an experimental painkiller -- even though it actually contained nothing but salt water -- most of them reported a decrease in the pain they felt from a previous shot. We may call it "mind over matter," doctors call it the placebo effect.
"The placebo effect has been known for a long time," Zubieta says. "Specifically in the context of pain, there is a clear effect of reductions of pain ratings by subjects when they believe that they are receiving a substance that is active, even though it is really inactive."
In the early days of medicine when anatomy was poorly understood, the placebo effect — which occurs when a "dummy treatment" has positive therapeutic effects because a patient believes it will work -- was a crucial component of all medical treatment. As medical knowledge progressed, scientists began to make educated guesses as to how the placebo effect worked, hypothesizing that the human brain could make its own painkilling chemicals and release them under certain high-stress circumstances. But because of technological limitations, no one was able to objectively observe these chemical processes -- until now.
Opioids "plugging in" to a receptor. image: ABC News
As reported in Discover magazine, Zubieta used PET brain scanner to take pictures of the placebo effect in action for the first time, confirming what scientists had suspected for decades: In the patients who said the placebo relieved their pain, he saw that the brain did indeed produce its own natural pain-killing chemicals. Called opioids, these chemicals plug into tiny "sockets" on nerve cells, called mu-opioid receptors, the same way medications like morphine do -- dulling or eliminating feelings of pain.
"We suspected that that was the case, and there was evidence suggesting that the experience of pain was mediated by these receptors," Zubieta says. "It's probably a mechanism that has been there since the beginning of time, giving us resiliency and allowing us to adapt to the environment in an appropriate fashion -- say, in a fight against an animal. If you're in the middle of fighting for your life, you do not want to be stopped by an injury."
While animal ambushes are no longer a constant threat for most people, Zubieta hopes that harnessing the power of the placebo effect will lead to better ways of managing pain in hospitals.
"Of course you don't want to lie to people, but you do want to create a situation sometimes that does help promote these effects," he explains. "For example, in a doctor's office, having confidence that the doctor will know what to do for your illness -- that by itself will create a placebo effect."
But Zubieta says that even with this knowledge, we will probably never fully conquer the problem of pain -- because, although it might be easy to forget when you cut your finger or stub your toe, feeling pain is actually a crucial part of staying healthy.
A PET scanner.
"Pain is important for the individual to understand that there is an injury, so it's actually quite difficult to completely eliminate pain. In fact, it can be dangerous," Zubieta says. "If you have an injury and there is no danger around you, you want to know where the pain is and how severe it is, so you can take care of yourself."
Zubieta says that the next step is to figure out why some people have more mu-opioid receptors than others, or why some people's receptors are more powerful than others' at reducing pain. He also believes that a better understanding of the placebo effect will also make drug development more efficient, since it "is often considered a nuisance variable or a bias in the patients" when new drugs are being tested.
"What this research is telling us is that beyond the traditional ways of managing pain or dealing with disease, there are areas in our brains that take advantage of our own abilities, our own resiliencies, to be able to compensate for injury," he says. "And the trick will be figuring out how to harness that better."
Which means that a little pain today may provide a lot of gain tomorrow.
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