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Sunday, August 8, 2010

Placebos: All you never wanted to know (Part 3a) - Experimental Evidence

Well, here we are again to continue on our tour of research surrounding the knife in Descartes eye, the placebo effect.

I wonder sometimes if mind-body dualism hadn't become so popular, would we have learned to understand the placebo effect long before now?

In any case, Part 3 (Parts 1 and 2) of this series is going to look at experimental evidence surrounding the placebo effect. This section may end getten broken up some more, but we will cross that bridge when we come to it.

An interesting study took place in the heady days of 2006 (Kaptchuk et al 2007) and involved some of the biggest names in the field. The study set out to examine the differential effects of two wholly placebo treatments. They used a sham acupuncture treatment and also the traditional sugar pill. Now, if placebo effects were an illusion, one would not expect to see a difference between these two treatments, but thats not what was seen.

The study was an 8 week randomised controlled trial (sortof, given that there was no active ingredient), and the results showed that the two placebos were mostly the same, except that the pill group showed increased hand grip (which was measured objectively, for those of you who care about such things).

The next study is far more interesting, however. Again its Kaptchuk et al, 2008 this time though. Essentially it was a randomised controlled trial of acupuncture with three groups using patients suffering from Irritable Bowel Syndrome.
The first group was the no treatment control. They came in, they took part, but didnt have any treatment.
The second group was minimal contact group. These people received either real or fake acupuncture, but delivered in a business like fashion, and they didnt spend very much time with each patient.
The third group was enhanced acupuncture which had the therapist come in and talk to them for about half an hour before putting in the needles.

At the six week outcome measure point, 3% of group 1, 20% of group 2 and 37% of group 3 had significant improvement (all differences between the groups significant at the p<0.0001 level). This to me is pretty amazing. If a treatment which doesnt tend to do well in clinical trials (acupuncture) augmented by warm and friendly interaction with another can be this effective, how much more effective would it be with a well validated treatment? Its perhaps sad that doctors are now so focus on diagnosing and dismissing that they are not making much of an effort with their relationship with their patients, and this is having a measureable impact on their healing capacities. Anyway, moving on to some fascinating work by Geers et al. In this study student participants took a pill which purported to increase their anxiety and irritableness. However, Geers added a number of interesting modifications to this study. Again, there were 3 main groups in the study. Group 1 - this drug is active and will increase your irritability Group 2- you may or may not get the active drug Group 3 - you are getting a placebo. Geers also measured optiimism levels at baseline. The major findings were as follows. The participants in the deceptive administration group tended to show more of an effect than those in groups 2 or 3. However, optimism mediated these results as those high in optimism tended not to respond to the nocebo suggestion, while those high in pessimism tended to respond much more to the nocebo suggestion. These interesting finding may explain why optimists tend to have better health outcomes than pessimists. So, the take home message is this: be optimistic about your medical treatments, it just might save your life. I hope to get another post on this experimental evidence section up for all of you sometime in the next few days.

Kaptchuk, T. (2006). Sham device v inert pill: randomised controlled trial of two placebo treatments BMJ, 332 (7538), 391-397 DOI: 10.1136/bmj.38726.603310.55

Kaptchuk, T., Kelley, J., Conboy, L., Davis, R., Kerr, C., Jacobson, E., Kirsch, I., Schyner, R., Nam, B., Nguyen, L., Park, M., Rivers, A., McManus, C., Kokkotou, E., Drossman, D., Goldman, P., & Lembo, A. (2008). Components of placebo effect: randomised controlled trial in patients with irritable bowel syndrome BMJ, 336 (7651), 999-1003 DOI: 10.1136/bmj.39524.439618.25

GEERS, A., HELFER, S., KOSBAB, K., WEILAND, P., & LANDRY, S. (2005). Reconsidering the role of personality in placebo effects: Dispositional optimism, situational expectations, and the placebo response Journal of Psychosomatic Research, 58 (2), 121-127 DOI: 10.1016/j.jpsychores.2004.08.011


  1. "So, the take home message is this: be optimistic about your medical treatments, it just might save your life. "

    A little simplistic. People can't just change like that, and neither should they. The modern view that optimism = good and pessimism = bad, is just too superficial to taken seriously. There is good evidence that the so called 'pessimistic' type have more realistic perceptions of certain situations than the 'optimistic' type. Takes all types in a social species to cover the bases.

    But such nuance does not sit comfortably with the broader cultural prejudices, including within psychological science I regret to say.

    If our dear leaders had been a bit more pessimistic (ie cautious) about going into Iraq, for example, they might have had a much more realistic view of how difficult it was going to be and hence they might have handled it a lot better overall. (Note, this is not an argument for or against going into Iraq, just about how it was done.)

  2. Yes, this is true, and these are valid points. Actually, some of my recent research suggests that optimism may actually be bad for your health!

    However, there is a big difference between optimism as generalised positive expectancies, and optimism as a blind faith Pollyanna like that things will work out, regardless of evidence.

    Pessimists seem to have less self confirming biases, this is true, but they also tend to have less successful careers, lives and families.

    I suppose the trick is to trust (your positive expectancies) but verify (that you're not heading off a cliff).

    And also, there are a number of valdiated ways to increase optimism. The ABCDE method of Seligman, for example:

    On the whole Iraq thing, it was obvious to me at least that the reasons given for going in were not the real reasons, so i probably wouldn't count that as an example of unrealistic optimism.