The field of mental health studies has made massive strides over the last few decades, and we have a better understanding of how the human mind works than ever before.

There’s one mystery, however, that has baffled neurologists and psychiatrists alike – no one seems to be able to find a single case of schizophrenia in a person who was born blind.

Scientists around the world have looked into the phenomenon. A 2018 study at the University of Western Australia looked at nearly half a million children born between 1980 and 2001, strengthening the case for the connection between congenital blindness and immunity to schizophrenia.

Conversely, loss of sight later in life is associated with a higher risk of schizophrenia and psychotic symptoms.

VICE spoke to psychiatrist and researcher Tom Pollak, who has made it his mission to figure out this all works.

We’ve known for a long time about the link between vision loss and hallucination. Charles Bonnet syndrome, first described in 1760, is a disorder in which people lose their vision and then start to experience hallucinations. These kinds of mental conjurings don’t necessarily come with mental illness, though people with schizophrenia have been regularly shown to also have issues with their sight.

People born without sight don’t seem to have this problem, and Pollak, along with co-author Phil Corlett, thinks they might know why. They published a study in the journal Schizophrenia Bulletin:

It’s rooted in the hypothesis that one of our brain’s most important jobs is to make predictions about the world.

This view of the brain argues that rather than perceiving the world around us in real time, our brains create a model of what’s out there, predict and simulate what we experience, and then compare our predictions to what’s actually happening—using any errors to update or change the model in our minds. The accuracy of your past predictions are crucial for the accuracy of your overall model—it’s what you’re comparing new inputs to, and how you’re making any adjustments.

Enter vision, which is one of the ways that we collect information about the world around us. Vision helps us to link together with other sensory cues like touch, sight, and smell.

For example, if you touch a cactus, and it pricks your finger, your vision makes the association between cacti and pain. The next time you see a cactus, you won’t have to touch it to know that it’s prickly, and should be avoided.

If the way a person sees the world is off, it can make it harder to predict, correct errors, and build a model of the world that makes sense. And when people have problems with their vision, the brain has to make more predictions to explain them. On the other hand, if you couldn’t see anything, you wouldn’t build up those false representations of the world around you—which could lead to problems in thinking later on.

This could go a long way to explaining all of the problems with vision and sensory processing that people with schizophrenia experience in early life. At the same time, it explains why people who are born blind, don’t seem to suffer from the condition.

You can read the full article here, which includes a look at psychiatrist Steve Silverstein’s study on the ways that blindness can significantly improve cognitive ability.

If you, or someone you know struggles with mental health, and you need a little help, you’ll find a list of free mental health resources when you follow this link.

[source:vice]