A long-standing enigma in psychiatry has been why no-one has been able to find someone who has both congenital blindness and a diagnosis of schizophrenia. The newest and most comprehensive archive study to date has just been published on exactly this issue although it raises more questions than it answers.
Evelina Leivada and Cedric Boeckx from the University of Barcelona in Spain conducted an extensive medical literature search and did come up with some cases of congenital blindness and schizophrenia – 13 in total, although only two case studies (outlining a total of four cases) were found which were convincing enough to be unaffected by other serious problems, like severe genetic disorders.
And these remaining four were hardly straightforward and as one report was from 1943 and the other from 1967 where standards of both vision and psychiatric assessment were significantly short of modern standards.
Notably, all cases of co-occurrence were from blindness due to eye problems or where blindness happened relatively late (after 6 years of age). No cases were found were people had a diagnosis of schizophrenia and were congenitally cortically blind – where blindness was caused by problems with the brain’s visual system.
What this new study provides is weak evidence for the possibility of certain sorts of blindness coexisting with a diagnosis of schizophrenia and more comprehensive support for the curious finding that blindness seems to reduce the risk of developing psychosis.
It’s worth noting that what is really needed is a prospective epidemiological study of psychosis in blind people. However, researchers have been searching for congenitally blind people with psychosis since the issue of non-co-occurrence was first seriously raised in the 1980s and none have been found. Based on the rates of occurrence for each condition, the combination should be fairly common. This suggests that hypothesis of protective effects of congenital blindness needs to taken seriously.
The Leivada and Boeckx paper goes on to speculate about neuropsychological reasons why congenital blindness might protect against schizophrenia (essentially, changes in the interaction between key visual system components and the language system) and, somewhat less convincingly, genetic reasons – as just extrapolating likely genes from case studies is very speculative and both the eye and brain develop from the same cells during embryo development so it’s not clear shared genes won’t just reflect generally impaired neurodevelopment.
I have to say, I find the concept of schizophrenia to be a fairly useless, but if the increasingly plausible hypothesis that congenital blindness protects against psychosis is confirmed, it has interesting implications for those that argue that psychosis is nothing but the result of marginalisation, stigma or difficult life circumstances where biological explanations are irrelevant.
Blindness, clearly would increase your chances of all of these, and so on this theory, we would expect an increased rate of psychosis, but this doesn’t seem to be the case.
It’s not that marginalisation, stigma or difficult life circumstances aren’t causal factors in developing psychosis, they clearly are, but ignoring neuro-level explanations outside these effects is equally as narrow as suggesting that they are the only relevant influences.
Link to ‘Schizophrenia and cortical blindness’ in Frontiers.
Mind Hacks 
How likely would it be that researchers could find undiagnosed cases of schizophrenia? I’m just wondering if congenital blindness could in any way mask the condition or confuse physicians (especially 10 or 15 years ago) so it would remain undiagnosed.
Blind people miss visual social cues. Maybe the record for sound is more durable than that for sight so sound can/could be more easily reviewed for verification. I understand one of the criteria for schizophrenia is the overlapping or confusion of sight-sound-smell. With less input, there’d be less chance of misinterpretation. How can a schizophrenics mental CPU speed be rated?
That’s not one of the criteria for schizophrenia…it sounds like you’re thinking of synesthesia.
I think the claim was that sight reduces down unnecessary synapses, like is done as people enter into adulthood, and without sight more brain matter is retained. In schizophrenia too much is lost. I don’t think there is a CPU speed, if there was it might be related to dopamine levels. With schizophrenia and mania, thoughts can go too fast, get all jumbled up and meaningless (or overly meaningless and psychotic) and overlap each other often faster than the speed of vocalizing them. This is not productive like a fast CPU might be. If the CPU overheats and fails; that might be a better analogy. I’m bipolar, mania, true mania, is a very bad thing.
There is another explanation whereby emotion reading skills have been compromised by visual misinterpretation
of facial expression in the first months of life. Congenital blindness prevents this, a full explanation is given at
http://WWW.opendot.co.uk
I’ve seen a claim that at some some of what looks like mental problems are actually mental reactions to sensory problems.
Sorry, I can’t remember the book. If I remember correctly, it had a description of someone who seems to be paranoid but actually had a vision problem which made it seem as though stationary objects were coming at him.
A key to psychosis is abberant filtering of thalamocortical information. If this pathway is already misfunctioning in the case of someone with congenital blindness, then it follows that they probably couldn’t have overabundant activation of it as is thought to occur in psychosis.
This lends credence to a theory I once had concerning the nature of schizophrenia. I have what I consider to be an uncanny ability to see faces in many textures. I was always able to see the “man in the moon,” but one night, while stoned, I spotted a face in a weird table we had that was made up of crushed shells embedded in plastic. I found dozens. The more I looked, the more I found. None then or to date were very human-looking–they were mostly impish. But what if a schizophrenic isn’t aware that his mind is picking up on these images. I propose having a clinician take an ordinary image and show the schizophrenic that, “hey, I can spot faces too and they never hurt me.” The pictures can be created with a mask that can be superimposed on them to better enable the viewing of the “faces.” I would call it a therapeutic Rorschach where the therapist sees things similar to those seen by the patient.
…see no evil, manifest less evil?
see www. opendot.co.uk for how sight and the missing fear pheromone is the cause of the problem