Lack of vitamin D possible cause of schizophrenia | Hacker News Reader

Lack of vitamin D possible cause of schizophrenia

thestar.com

15 pointsadammichaelc18 comments

Quote that sums up the article:

The study, published this week in the journal Archives of General Psychiatry, used Denmark’s blood bank, which contains samples from almost every baby born in the country since 1982. It compared the blood of 424 people who developed schizophrenia to an equal number of those who did not.

The lead author, renowned schizophrenia researcher John McGrath, found that babies with a low level of the vitamin during fetal development and infancy had nearly two times the chance of developing the disease.

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.

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.

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.

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?

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.

Schizophrenia is a rare condition

Schizophrenia is actually a common disease, affecting ~1% of the world population, regardless of ethnicity.

Sounds about right. I suppose that makes it a relatively common condition, then.

It very sadly is. Many homeless people are among the affected.

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...

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/

At any rate, I don't disagree with your general points, I just thought you might be interested in the above refinements.

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.

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). 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.

Theories about the etiology of schizophrenia are a dime a dozen. I did my thesis on the genetics of schizophrenia 20 years ago, and to this day nothing has come of it.

If the research cited is not in one of the top journals, I'd not even bother reading the abstract.

Does "The Archives of General Psychiatry" count as one of the top journals?

To me that would be Science, Nature, Cell, not necessarily in this order.

These journals have the highest impact factor, which is "sort of like PageRank". You could compare this to the IF of the mentioned journal.

It is the psychiatric journal with the highest impact factor, considered a flagship of psychiatric research.

Society greatly underestimates the surprising pyschotropic efficacy of common foods and nutrients.

Let me guess. Your source for that would be a diet book written by some guy who spends half the book complaining that his theories are being dismissed by mainstream science?

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