A study carried out by The University of Western Australia (UWA) has provided compelling evidence that congenital/early cortical blindness—that is, when people are blind from birth or shortly after—is protective against schizophrenia.

The unusual discovery has fascinated scientists and may lead to a better understanding of what causes schizophrenia—a question that has baffled scientists for decades. Schizophrenia is characterized by symptoms such as losing touch with reality, hearing voices, and having visual hallucinations. However, despite numerous bodies of research, the exact cause still remains a mystery.

The UWA researchers used data collected from health registers between 1980 and 2001 on nearly half a million people in Western Australia and found that no one with a diagnosis of congenital or early cortical blindness developed schizophrenia. Lead author, professor Vera Morgan from the UWA Neuropsychiatric Epidemiology Research Unit in the Schools of Population and Global Health and Medicine said they also found no one with congenital or early cortical blindness had developed any other psychotic illnesses.

"This leads us to think there is a link that must be explored," she said. Professor Morgan said that the brain's plasticity could be the link. "It's very difficult to say what the exact mechanism is, but we think that the protective effect for schizophrenia is related to some kind of compensatory cortical reorganisation in the brain that's happening in response to having congenital or early cortical blindness," she said.

"As a result, some functions that are impaired in schizophrenia may actually be enhanced in people with congenital or early cortical blindness." Professor Morgan said the research had concentrated on people who were blind at birth or in their early years because there was greater brain plasticity at that age and greater potential for new neural connections to be formed.

"This research may have implications for intervention in the future. If we can understand what causes the protective effect and artificially reproduce this, we may be able to intervene early at a stage to minimize or prevent those symptoms that can lead to schizophrenia." The research has been published in the British Psychological Society Digest Report.