Could schizophrenia protect against blindness?

November 3, 2006 7:48 AM

This research claims that there aren't any blind schizophrenics. Basically, it says that blindness could protect against schizophrenia, but because of typically later age of onset for blindness (mostly results of glaucoma and macular degenration), I wonder if schizophrenia could somehow protect against blindness. Does anyone have an opinion on this?

Short Communication
No blind schizophrenics: Are NMDA-receptor dynamics involved?
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Glenn S. Sanders a1, Steven M. Platek a2 and Gordon G. Gallup Jr. a1
a1 Department of Psychology, State University of New York at Albany,
Albany, NY 12222 [e-mail] www.albany.edu/~gallup
www.evolutionarypsych.com
a2 Department of Psychology, Drexel University, Philadelphia, PA 19102
[e-mail] www.pages.drexel.edu/~smp43
Abstract
Numerous searches have failed to identify a single co-occurrence of total blindness and schizophrenia. Evidence that blindness causes loss of certain NMDA-receptor functions is balanced by reports of compensatory gains. Connections between visual and anterior cingulate NMDA-receptor systems may help to explain how blindness could protect against schizophrenia.

posted by srs to science & nature (15 answers total)

There are several questions I'd want to ask about this study:

1) what are their working definitions of "total blindness" and "schizophrenia"? The latter, in particular, is a much contested term in the hunt for the causes of schizophrenia, where much depends on where you draw the lines that demarcate schizophrenia. This is a perennial problem with the schizophrenia research I've read, as well as the secondary literature, and it does make a difference in what you might be looking at.

Coming at it from the other angle, they seem to be suggesting that the blindness they're interested in is congenital, and so they may be limiting their searches to congenital blindness, obviating your reading of the abstract.

2) I'd like to know the rates of mental illness in general in congenitally blind populations. This would be particularly useful because:

3) Schizophrenia presents differently in different cultures. (For instance, there are higher rates of catatonic schizophrenia in many Asian cultures, while there are higher rates of paranoid schizophrenia in the US. In general, though, there is strong acceptance of the fact that many mental illnesses are culture bound.)Not only is this a strong argument against a mechanistic, biologically-limited explanation for the etiology of schizophrenia, it might also mean that presentations of schizophrenia in blind patients are being overlooked in the research.

4) Are classic symptoms of schizophrenia, especially negative symptoms, simply being rolled into a general sense of how blind people act?

Regardless, at the present stage of research into the causes of schizophrenia, this seems like a concept paper leading to brain imaging studies.
posted by OmieWise at 8:22 AM on November 3, 2006 [1 favorite]

OmieWise, I could e-mail you the full article (pdf) if you like. Am I allowed to do that, or would it violate some stupid law towards keeping people blind?
posted by srs at 8:43 AM on November 3, 2006 [1 favorite]

No blind schizophrenics: Are NMDA-receptor dynamics involved?
Upper right for full pdf
posted by srs at 9:03 AM on November 3, 2006

Thank you OmieWise
posted by srs at 9:18 AM on November 3, 2006

I thought I read somewhere that cats were associated anecdotally with schizophrenia.

Not knowing how well guide dogs and cats get on in real life, could one hypothesize that blind people own significantly fewer cats (I don't know if this is true), and that consequently you might find significantly fewer people developing schizophrenia.

My point is that the pathway suggested (via brain mechanics) is conjectural. Maybe not as conjectural as my stream of consciousness, but there you go.
posted by blue_wardrobe at 9:29 AM on November 3, 2006

srs, spite won't win you any points in this roundtable. As the old barfly adage goes, say your peace, swallow your bitter.
posted by Smart Dalek at 9:29 AM on November 3, 2006

IANADoctor, but the arrow of causality very infrequently goes both ways. Think of any (medical or otherwise) causal pathway and reverse the direction--does it make sense? Typically not, so my money is on "no".
posted by jtfowl0 at 9:39 AM on November 3, 2006

I'm sorry Smart Dalek. My gratitude is sincere. Any and all comments/opinions regarding this issue are exceptionally appreciated. I'm not asking someone to write a paper for me, or do research for me. I am deeply curious about this issue and don't know enough to assess it myself, but I've noticed that a lot of neuroscientists read MeFi.
posted by srs at 9:52 AM on November 3, 2006

That is an absolutely fascinating abstract, srs. Thanks for asking this question.

The claims of the article look plausible to me. Lots of work has shown schizophrenics have larger ventricles in their brains, implying extensive cell loss in the brain, and NMDA receptors are excitotoxic, meaning they tend to lead to cell loss; so if blindness does something to inhibit some aspect of the NMDA system, that seems like a good mechanism to explain the very striking observation that "Numerous searches have failed to identify a single co-occurrence of total blindness and schizophrenia."

The question OmieWise raises, of congenital blindness as opposed to blindness later in life, led me to wonder if schizophrenics might be photophobic, but a quick Google search listed first a study which showed a degree of photophilia in schizophrenics! I would really like to see a study asking whether shizophrenics were photophobic at the onset of the disease.

I can't think of a way schizophrenia could prevent blindness.
posted by jamjam at 12:10 PM on November 3, 2006 [1 favorite]

There cannot possibly be no blind schizophrenics, either congenital or acquired. There are hundreds of utterly diverse causes of blindness apart from macular degeneration and glaucoma.
Their literature search strategies were quite poor, here's a case report of a schizophrenic man who blinded himself:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=12782931&query_hl=2&itool=pubmed_docsum
posted by roofus at 2:30 PM on November 3, 2006

Here are some interesting clues. Sources available upon request (I have too much work to do than look for it all right now).

Smoking might indirectly lead to blindness. Most schizophrenics smoke, but still (according to preliminary research in question) don't go blind. There is research that smoking helps schizophrenics not be so stupid. Schizophrenic man gouges his own eyes out. Schizophrenics less likely to "fall" for certain optical illusions and typically exhibit lower reactions in N400 ERP experiments.
posted by srs at 4:39 PM on November 3, 2006

As I said, I can supply citations for all of that if anyone wants them. I'm just writing it off the top of my head. I'm sorry that I don't have time to search for all of it right now. Also, can anyone suggest another place for me to post this question?
posted by srs at 4:41 PM on November 3, 2006

jamjam thank you. very interesting
posted by srs at 8:40 PM on November 3, 2006

blue_wardrobe: you're thinking of the toxoplasmosis connection with schizophrenia.
posted by kimota at 7:11 AM on November 4, 2006

FYI: "schizophrenia" has so many other risks involved that afflicted individuals are likely to die of other causes before blindness would normally kick in.
posted by srs at 1:14 PM on December 7, 2006