You might say that the persistence of witch doctors is weak evidence of the placebo effect. But I would guess that the nocebo effect (believing something is going to hurt you) would be stronger. This is because stress takes years off people’s lives. The Secret of Our Success cited a study of the Chinese belief that birth year affects diseases and lifespan. Chinese people living in the US who had the birth year associated with cancer lived ~four years shorter than other birth years.
I took a look at The Secret of Our Success, and saw the study you’re describing on page 277. I think you may be misremembering the disease. The data given is for bronchitis, emphysema and asthma (combined into one category). It does mention that similar results hold for cancer and heart attacks.
I took a look at the original paper. They checked 15 diseases, and bronchitis, emphysema and asthma was the only one that was significant after correction for multiple comparisons. I don’t agree that the results for cancer and heart attacks are similar. They seem within the range of what you can get from random fluctuations in a list of 15 numbers. The statistical test backs up that impression.
If this is a real difference, I would expect it has something to do with lifestyle changes, rather than stress. However, it’s in the opposite direction of what I would expect. That is, I would expect those with a birth year predisposed to lung problems to avoid smoking. I did find some chinese astrology advice to that effect. Therefore they should live longer, when in fact they live shorter. So that doesn’t really make sense.
This result seems suspicious to me. First of all because it’s just a couple of diseases selected out of a list of mostly non-significant tests, but also because people probably do lots of tests of astrology that they don’t publish. I wouldn’t bet on it replicating in another population.
Thanks for digging into the data! I agree that the rational response should be if you are predisposed to a problem to actively address the problem. But I still think a common response would be one of fatalism and stress. Have you looked into other potential sources of the nocebo effect? Maybe people being misdiagnosed with diseases that they don’t actually have?
From a quick look on Wikipedia I don’t see anything. Except for patients that report side effects from placebo, but of course that could be symptoms that they would have had in any case, which they incorrectly attribute to the placebo.
I don’t see how you could get an accurate measure of a nocebo effect from misdiagnoses. I don’t think anyone is willing to randomize patients to be misdiagnosed. And if you try to do it observationally, you run into the problem of distinguishing the effects of the misdiagnosis from whatever brought them to the doctor seeking diagnosis.
You might say that the persistence of witch doctors is weak evidence of the placebo effect. But I would guess that the nocebo effect (believing something is going to hurt you) would be stronger. This is because stress takes years off people’s lives. The Secret of Our Success cited a study of the Chinese belief that birth year affects diseases and lifespan. Chinese people living in the US who had the birth year associated with cancer lived ~four years shorter than other birth years.
I took a look at The Secret of Our Success, and saw the study you’re describing on page 277. I think you may be misremembering the disease. The data given is for bronchitis, emphysema and asthma (combined into one category). It does mention that similar results hold for cancer and heart attacks.
I took a look at the original paper. They checked 15 diseases, and bronchitis, emphysema and asthma was the only one that was significant after correction for multiple comparisons. I don’t agree that the results for cancer and heart attacks are similar. They seem within the range of what you can get from random fluctuations in a list of 15 numbers. The statistical test backs up that impression.
If this is a real difference, I would expect it has something to do with lifestyle changes, rather than stress. However, it’s in the opposite direction of what I would expect. That is, I would expect those with a birth year predisposed to lung problems to avoid smoking. I did find some chinese astrology advice to that effect. Therefore they should live longer, when in fact they live shorter. So that doesn’t really make sense.
This result seems suspicious to me. First of all because it’s just a couple of diseases selected out of a list of mostly non-significant tests, but also because people probably do lots of tests of astrology that they don’t publish. I wouldn’t bet on it replicating in another population.
Thanks for digging into the data! I agree that the rational response should be if you are predisposed to a problem to actively address the problem. But I still think a common response would be one of fatalism and stress. Have you looked into other potential sources of the nocebo effect? Maybe people being misdiagnosed with diseases that they don’t actually have?
From a quick look on Wikipedia I don’t see anything. Except for patients that report side effects from placebo, but of course that could be symptoms that they would have had in any case, which they incorrectly attribute to the placebo.
I don’t see how you could get an accurate measure of a nocebo effect from misdiagnoses. I don’t think anyone is willing to randomize patients to be misdiagnosed. And if you try to do it observationally, you run into the problem of distinguishing the effects of the misdiagnosis from whatever brought them to the doctor seeking diagnosis.