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In Joseph Henrich's book The secret of our Success he discusses the importance of culture as a factor in the rise to success of Homo sapiens.

In chapter 14 he specifically discusses examples where culture has large effects on people's biology. The chapter includes a discussion about placebos and nocebos (the opposite to placebos: inert things that make you feel worse). He notes:

...the action and effectiveness of a placebo often depends entirely on how much faith a patient puts in a particular placebo or medical treatment. The more you believe it will work, the more it may actually work...

The same, he argues, applies to nocebos. He quotes a particular example based on Chinese astrology. In short, people born on particular Chinese years are thought to be susceptible to diseases connected to the spirit of that year.

This is testable:

The prediction is that the combination of getting a particular disease and being born in a year that is believed to be associated with the relevant symptoms or organs of that condition will result in an earlier death. Chinese Americans with an unfavorable disease–birth-year combination can be compared against both Chinese Americans with different disease–birth-year combinations and with white Americans with the same diseases but who presumably don’t put much weight on traditional Chinese astrological beliefs.

And he claims it seems to be true for example for bronchitis, emphysema and asthma (associated with the lungs and therefore unfavourable in birth years ending in 1 or 0):

Looking at all Chinese Americans, females lose four years of life and males lose five. Since many Chinese Americans may no longer put much stock in traditional Chinese astrology, it’s worth looking at those living in the larger Chinese communities in Los Angeles and San Francisco and those born in China, because these populations are more likely to have retained traditional beliefs. For men, the picture doesn’t change much, but the years of life lost by women go as high as nine years. Similar patterns emerge for cancer and heart attacks.

So, basically, the death rate is higher for some Chinese groups in years though to be unfavourable according to Chinese traditional astrology.

He also points out that these observations clearly don't apply to Americans who don't have any cultural background in Chinese beliefs.

But this sounds like a pretty significant effect (but then, so is the placebo effect). Can the effect of belief in tradition have such a strong effect on mortality?

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    Note that there is a second mechanism that could apply here--people with such a diagnosis and the unfavorable birth year might consider the situation hopeless and thus not treat it as aggressively as someone else. Oct 31 '18 at 7:58
  • It certainly affected birth rates: en.m.wikipedia.org/wiki/Hinoe_uma Apr 17 at 5:38
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I was also wondering about this, seems like too large of an effect just due to astrology beliefs.

Here is what I found: a 2006 study The five elements and Chinese-American mortality re-examined and attempted to replicate the result.

A more complete statistical analysis and independent California mortality data for the years 1960-1968 and 1991-2002 did not replicate the original results.

[...]

Phillips et al. (1993) reported that California mortality data for 1969–1990 indicated that Chinese Americans were unusually vulnerable to diseases of the zang and fu organs associated with their birth year. However, among those Chinese Americans dying of the 15 narrowly defined diseases that were reported, almost exactly 20% had birth years associated with that organ—just what one would expect if birth year were irrelevant.

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