On Needles and Nothing

As reported yesterday by Amanda Gardner at Health.Com (and re-posted on CNN.Com), "Acupuncture Works, One Way or Another." The article reports on a recently published meta-analysis of 29 studies comparing pain relief from real acupuncture to placebo acupuncture (usually needles that are placed outside of known pressure points) to no treatment.

The common measure of efficacy for such studies is a 50 percent reduction in pain, as measured on a 100 point scale (dropping from 80 to 40 for example). Accordingly, real acupuncture achieved this rate of pain reduction 50 percent of the time, placebo acupuncture met this mark 43 percent of the time, and people who weren't needled at all felt this level of pain relief 30 percent of the time.

This is better than acupuncture's usual showing. In many studies, it does no better than placebo. On the other hand, about two thirds of the difference in pain relief between no treatment and acupuncture is accounted for by placebo.

This likely isn't the final word on the efficacy of acupuncture. But I'd like to bring up one other interesting finding about the treatment. A few years ago, the German health authorities (the volks who decide what treatments will be covered under their national healthcare plan) compared acupuncture to sham acupuncture and to several other known (and already covered) treatments for chronic lower back pain, including medication and physical therapy. Acupuncture did no better than sham acupuncture in these trials. But both real and sham acupuncture beat the therapies that were already approved!

Subliminal Placebos!

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.

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.