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Schizophrenia: how the outer and inner world affects the voices in the head

Schizophrenia is a chronic, severe, and disabling brain disorder. It can cause people to have trouble distinguishing between what is real and what isn't. People with schizophrenia may hear voices that are not there or believe that other people are reading their minds, controlling their thoughts, or plotting to harm them.
Schizophrenia affects the way someone thinks about themselves and interacts with others. People who experience symptoms of schizophrenia may seem like they don't care about anything; they may sit for hours without moving or talking; they may refuse food; they might talk so fast no one else can keep up (this is called "pressured speech"). They might also be very sensitive to things like light or loud noises (especially if these stimuli aren't usually a problem for them); or they might cover their faces with their hands and/or cry, as if an intense sadness is never going to end.
One of the main symptoms of schizophrenia is hearing voices in the head (auditory hallucinations). Up to 75% of diagnosed patients have it. Some people report that voices are always there, while others only hear them from time to time. Voices can be soft and calming, or they can be harsh and demanding. Why do some patients hear disturbing voices that bother them, while others don't face such problems.
A recent study of auditory hallucinations in schizophrenic patients suggests that cultural background may play a decisive role in which voices a person hears. 60 people from USA, India and Africa with a diagnosis of schizophrenia were asked to describe what voices they hear. The results showed that American participants had mostly negative experiences with hallucinations, they described them as torturing and violent, and some even compared them to a call to battle.
On the other hand, participants from India and Africa described voices as positive and even calming. Most of Indian participants heard voices of their relatives giving them tasks or advice and described them as mostly positive and sometimes even entertaining. African members also generally referred to voices as good and considered them to be the voice of god.
What about deaf people? Do they hear voices as well? 2007 ULC study of 27 deaf participants with schizophrenia diagnosis showed that individuals born profoundly deaf were not able to experience auditory hallucinations. Instead, they saw visual hallucinations in their minds of either sign language or moving lips that they could read. All participants knew the gender and age of the person talking to them, without actually seeing or hearing the person.
What about blind people with schizophrenia? Do they experience visual or auditory hallucinations? 2019 study suggests that people who are blind from birth cannot get schizophrenia at all. The theory behind this finding is that people without a visual representation of their environment have a simpler model of the world that is less likely to be misinterpreted by the brain. Conversely, people who lose their eyesight later in life are more likely to suffer from various hallucinations, because their brain, which previously relied mainly on vision, will make less accurate predictions based on incoming information, which leads to hallucinations.
Schizophrenia has been known for over a century now, and while it is still not entirely clear what causes this mental disorder, recent research has shown that the way a person perceives the world around them plays a vital role in how the disorder manifests itself.


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