Almost 75 years ago, researchers noticed a strange pattern that remains one of the most puzzling in psychiatry: among people who are blind from birth due to damage to the brain’s visual cortex, schizophrenia is virtually never observed, writes The Conversation.

In 1950, writer Hector Chevigny, who lost his sight later in life, and psychologist Sydeil Braverman studied the psychology of blind people and noticed an unusual fact: a severe mental disorder found in almost all societies around the world seemed to be completely absent in people with congenital blindness.

For a long time, this observation was largely ignored — scientists lacked sufficient data and a clear understanding of schizophrenia itself. However, in the early 2000s, with the emergence of large national medical databases, researchers were able to track people’s health from birth into adulthood. The pattern was confirmed.

The most convincing evidence came from a 2018 study covering nearly half a million children born in Western Australia between 1980 and 2001. Schizophrenia developed in 1,870 individuals, but none of the 66 children with cortical blindness were diagnosed with the disorder.

Importantly, this protection does not appear to be linked to blindness itself, but specifically to how the visual areas of the brain develop. People who lose their sight later in life, or those blind due to eye damage rather than damage to the visual cortex, can still develop schizophrenia.

Scientists believe the explanation lies in how the brain uses vision to construct its model of the world.

Today, schizophrenia is increasingly viewed as a disorder of the brain’s predictive system. Normally, the brain constantly forms expectations about the environment and compares them with incoming sensory signals. In schizophrenia, this mechanism becomes disrupted: random or weak signals gain excessive importance, coincidences appear meaningful, and one’s own thoughts may be perceived as coming from outside. The boundary between imagination and reality gradually becomes blurred.

Vision plays a particularly important role in shaping this system in early childhood. The visual cortex is one of the largest and most highly interconnected regions of the brain, involved not only in processing images but also in learning, attention, and emotions.

If the visual cortex receives no input from birth, the brain develops differently. MRI studies show that in people with congenital cortical blindness, these areas are often “repurposed” for language, memory, and logical thinking.

Some researchers suggest that this early reorganization may provide a kind of protection. Without a constant stream of ambiguous visual input, the brain may develop more stable ways of interpreting the world, potentially reducing the risk of the faulty “predictions” that underlie schizophrenia.

Timing appears to be crucial. Losing vision later in life — even in childhood — does not provide the same effect, because the brain has already developed under the influence of visual experience.

Scientists emphasize that this does not mean blindness can be considered a practical “protection” against schizophrenia. However, these findings offer a new perspective on the nature of the disorder and may open up new approaches to treatment.