3 ms·

Thanks for the quote. There is a bit of correlation-causation concern here. For example, it is possible that whatever causes the decreased Vitamin D also causes

Thanks for the quote. There is a bit of correlation-causation concern here. For example, it is possible that whatever causes the decreased Vitamin D also causes schizophrenia. It need not be some chemical, either; it could be tied to behavioral or even genetic problems. For example (no truth to this that I know of but for sake of discussion): "Parents with a genetic predisposition to schizophrenia have tendencies that make them are less likely to provide proper nutrition or typical sun exposure to their children. Thus, those with a genetic predisposition for schizophrenia also have lower vitamin D, though that is entirely outside the causal chain." That (made-up) hypothesis would fit just as well as the "Vitamin D is in the causal chain" hypothesis, no? Given the uncertainty--and the suggestive epidemiological associations--this seems like an excellent subject for a clinical trial. I seem to recall that one is actually occurring (though perhaps for a different disease), but I can't find the link.

hugh3 16y ago
We're still talking about awfully low levels. Schizophrenia is a rare condition, and doubling your chances of getting a rare condition still leaves it as a rare condition. When a risk factor for a rare disease merely increases the risk by a factor of two it's usually not worth worrying too much about, and it'll probably remain too difficult to sort out the cause-and-effect. And yet, I can guarantee that many people reading this article will immediately take it to heart that "not getting enough sun during pregnancy causes schizophrenia" and make it a part of their personal belief structure. Perhaps the worst effects will be on the mother of schizophrenics, who having just got over the Freudian hangover in which all mental illnesses are blamed on the failings of the parents, will now be able to blame themselves for wearing too much sunscreen during pregnancy.
- carbocation 16y ago
  I agree. There will be plenty of victim-blaming going on here if people read too much into the epidemiology. Thinking about the implications of your comment for my suggestion of a clinical trial, I realized the following: powering a clinical trial to detect any change in the incidence of such a rare disorder is going to require tens or perhaps hundreds of thousands of participants. This sounds absurd but may actually be possible, given how much interest there is in vitamin D lately (faddist, IMHO, but whatever). Possible because (1) social interest; (2) vitamin D is cheap; (3) vitamin D is likely relatively safe at typical doses.
  - hugh3 16y ago
    Aren't you overlooking the really big problem that such a study would have to last all the way from pre-birth to adulthood in order to pick up this effect?
    - carbocation 16y ago
      I actually think that this is happening in some Scandinavian country (literally from birth). Apologies that I can't find the link, and I encourage you not to believe me until I can.
- car 16y ago
  Schizophrenia is a rare condition Schizophrenia is actually a common disease, affecting ~1% of the world population, regardless of ethnicity.
  - hugh3 16y ago
    Sounds about right. I suppose that makes it a relatively common condition, then.
    - car 16y ago
      It very sadly is. Many homeless people are among the affected.
  - carbocation 16y ago
    What you say is in agreement with the common wisdom. However, I'll offer two caveats: It may be no more than a myth that schizophrenia affects all ethnicities equally, according to a review of the data: http://schizophreniabulletin.oxfordjournals.org/content/32/1/195.full http://schizophreniabulletin.oxfordjournals.org/content/32/1... According to a systematic review, it appears that ~0.4% of the world population is affected (lifetime prevalence), not 1%: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1140960/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1140960/ At any rate, I don't disagree with your general points, I just thought you might be interested in the above refinements.
    - car 16y ago
      Thank you for making this more specific. I checked on Wikipedia after my comment, and found what you cite. So common wisdom needs to adapt.
adammichaelc 16y ago
One thought that comes to mind is the theory that a certain virus or set of virus's causes schizophrenia, but only when one contracts those viruses at a very young age or when one's mother has the virus during pregnancy (see http://pn.psychiatryonline.org/content/39/10/1.2.full http://pn.psychiatryonline.org/content/39/10/1.2.full). It is well-known that lower vitamin D levels lead to a weaker immune system generally, so the correlation between getting schizophrenia later in life and early-infant Vitamin D levels could suggest that the causation is actually the virus, and that the lower Vitamin D level simply makes one more susceptible to said virus.

hugh3 16y ago

We're still talking about awfully low levels. Schizophrenia is a rare condition, and doubling your chances of getting a rare condition still leaves it as a rare condition. When a risk factor for a rare disease merely increases the risk by a factor of two it's usually not worth worrying too much about, and it'll probably remain too difficult to sort out the cause-and-effect. And yet, I can guarantee that many people reading this article will immediately take it to heart that "not getting enough sun during pregnancy causes schizophrenia" and make it a part of their personal belief structure. Perhaps the worst effects will be on the mother of schizophrenics, who having just got over the Freudian hangover in which all mental illnesses are blamed on the failings of the parents, will now be able to blame themselves for wearing too much sunscreen during pregnancy.

carbocation 16y ago
I agree. There will be plenty of victim-blaming going on here if people read too much into the epidemiology. Thinking about the implications of your comment for my suggestion of a clinical trial, I realized the following: powering a clinical trial to detect any change in the incidence of such a rare disorder is going to require tens or perhaps hundreds of thousands of participants. This sounds absurd but may actually be possible, given how much interest there is in vitamin D lately (faddist, IMHO, but whatever). Possible because (1) social interest; (2) vitamin D is cheap; (3) vitamin D is likely relatively safe at typical doses.
- hugh3 16y ago
  Aren't you overlooking the really big problem that such a study would have to last all the way from pre-birth to adulthood in order to pick up this effect?
  - carbocation 16y ago
    I actually think that this is happening in some Scandinavian country (literally from birth). Apologies that I can't find the link, and I encourage you not to believe me until I can.
car 16y ago
Schizophrenia is a rare condition Schizophrenia is actually a common disease, affecting ~1% of the world population, regardless of ethnicity.
- hugh3 16y ago
  Sounds about right. I suppose that makes it a relatively common condition, then.
  - car 16y ago
    It very sadly is. Many homeless people are among the affected.
- carbocation 16y ago
  What you say is in agreement with the common wisdom. However, I'll offer two caveats: It may be no more than a myth that schizophrenia affects all ethnicities equally, according to a review of the data: http://schizophreniabulletin.oxfordjournals.org/content/32/1/195.full http://schizophreniabulletin.oxfordjournals.org/content/32/1... According to a systematic review, it appears that ~0.4% of the world population is affected (lifetime prevalence), not 1%: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1140960/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1140960/ At any rate, I don't disagree with your general points, I just thought you might be interested in the above refinements.
  - car 16y ago
    Thank you for making this more specific. I checked on Wikipedia after my comment, and found what you cite. So common wisdom needs to adapt.

adammichaelc 16y ago

One thought that comes to mind is the theory that a certain virus or set of virus's causes schizophrenia, but only when one contracts those viruses at a very young age or when one's mother has the virus during pregnancy (see http://pn.psychiatryonline.org/content/39/10/1.2.full http://pn.psychiatryonline.org/content/39/10/1.2.full). It is well-known that lower vitamin D levels lead to a weaker immune system generally, so the correlation between getting schizophrenia later in life and early-infant Vitamin D levels could suggest that the causation is actually the virus, and that the lower Vitamin D level simply makes one more susceptible to said virus.