We don't need a doctor's suggestion to trigger placebo effects. Maybe we don't even need to think, not consciously anyway, according to a just-released study in the Proceedings of the National Academy of Sciences.
Alongside studies of verbal-suggestion ("this will dull your pain" etc), much research has looked into conditioned placebos -- in which people learn to associate some inactive stimulus (a medicine smell, for instance, or a sweet taste) paired with active drugs (much in the same way bells were paired with food in Pavlov's dog experiments). Soon enough, the medicine smell or the sweet taste by itself is able to have some of the same effects as the active drug.
In pain research, placebos and nocebos (the expectation of more pain), scientists usually condition people with a visual cue -- a specific color or shape paired with more or less pain. In this new pain study, however, both placebo and nocebo effects were triggered with images that flashed by the subjects so fast they could not detect them consciously. The researchers, led by Karin Jensen, a psychiatrist at Massachusetts General Hospital, were affiliated with the new Program in Placebo Studies at Boston's Beth Israel Hospital.
Here's how it worked: At first, subjects' arms were singed repeatedly with high or low heat pain, while viewing one of two faces (shown below). The subjects were asked to rate each burning pain from 0 to 100. The mean high heat score was 63, while the mean low heat score was 24.
LOW HEAT
[From Jensen et al., (2012) PNAS, "Nonconscious Activation of Placebo and Nocebo Pain Responses"]
In the second round, every heat stimulus was the same, medium intensity, randomly paired with one or another face. As expected, medium heat was felt more keenly (mean 53) when paired with a high heat face compared to a low heat face (mean 19). Finally, subjects sat through one more round of arm singeing paired with faces. This time, however, the faces blinked onto the screen for just 12 milliseconds, well below the threshold for conscious awareness. Still, they got the same results -- a mean pain rating of 44 for subliminal high heat faces and a mean of 25 for subliminal low heat faces.
These findings support the idea that patients' pick up on the subtlest of cues from the context of medical care, and that, in many cases these cues have a medical effect. For instance, consider the possible expectations communicated, without a word being said, by a doctor giving a treatment she is fully confident will work versus one about which she has significant doubts. Whether we're aware of it or not, our brains are constantly learning, and creating links in our minds that can have real effects on our bodies.
Alongside studies of verbal-suggestion ("this will dull your pain" etc), much research has looked into conditioned placebos -- in which people learn to associate some inactive stimulus (a medicine smell, for instance, or a sweet taste) paired with active drugs (much in the same way bells were paired with food in Pavlov's dog experiments). Soon enough, the medicine smell or the sweet taste by itself is able to have some of the same effects as the active drug.
In pain research, placebos and nocebos (the expectation of more pain), scientists usually condition people with a visual cue -- a specific color or shape paired with more or less pain. In this new pain study, however, both placebo and nocebo effects were triggered with images that flashed by the subjects so fast they could not detect them consciously. The researchers, led by Karin Jensen, a psychiatrist at Massachusetts General Hospital, were affiliated with the new Program in Placebo Studies at Boston's Beth Israel Hospital.
Here's how it worked: At first, subjects' arms were singed repeatedly with high or low heat pain, while viewing one of two faces (shown below). The subjects were asked to rate each burning pain from 0 to 100. The mean high heat score was 63, while the mean low heat score was 24.
HIGH HEAT
LOW HEAT
[From Jensen et al., (2012) PNAS, "Nonconscious Activation of Placebo and Nocebo Pain Responses"]
In the second round, every heat stimulus was the same, medium intensity, randomly paired with one or another face. As expected, medium heat was felt more keenly (mean 53) when paired with a high heat face compared to a low heat face (mean 19). Finally, subjects sat through one more round of arm singeing paired with faces. This time, however, the faces blinked onto the screen for just 12 milliseconds, well below the threshold for conscious awareness. Still, they got the same results -- a mean pain rating of 44 for subliminal high heat faces and a mean of 25 for subliminal low heat faces.
These findings support the idea that patients' pick up on the subtlest of cues from the context of medical care, and that, in many cases these cues have a medical effect. For instance, consider the possible expectations communicated, without a word being said, by a doctor giving a treatment she is fully confident will work versus one about which she has significant doubts. Whether we're aware of it or not, our brains are constantly learning, and creating links in our minds that can have real effects on our bodies.
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