Myth / Schizophrenia is caused by evil spirits or witchcraft.
Fact / There is a multitude of misconceptions about the cause of schizophrenia:

• Schizophrenia is not caused by a "curse or an evil eye."
• Schizophrenia is not God’s punishment for family sins.
• Schizophrenia is not caused by a lack of faith in God.
• Schizophrenia is not a form of demonic possession.
• Schizophrenia is not a result of frustrated love.
• Schizophrenia is not caused by reading too many books.

The genetic hypothesis / Relatives of people with schizophrenia have a greater risk of developing the illness than others. This risk is progressively greater in relatives who are more genetically similar to the person with schizophrenia. Below is a chart showing the increasing probability that someone will develop schizophrenia.
     Genetic factors appear to be important in the development of schizophrenia, but they are not sufficient to explain the entire pattern of occurrence. If an illness is entirely caused by genetic factors then identical twins share the same risk of the illness. That is, if one identical twin has the illness, the other should too. (In fact, in most studies of identical twins in which one twin has schizophrenia it is rare to find more than half of the other members of the pairs also affected.)

More than one hypothesis / That means that schizophrenia is not a simple, inherited disease, but rather what is called a complex genetic disease, which may have a variety of "triggers".
     Researchers believe that a predisposition to develop schizophrenia is inherited, but an environmental "trigger" must also be present to bring on the disease. Possible triggers are:

• Complications during the mother’s pregnancy or labour;
• Prenatal exposure to virus, specifically during the fifth month of the mother’s pregnancy, when most brain development occurs;
• It is thought that complications during pregnancy and delivery increase the risk, probably because of damage to the developing brain;
• Studies have shown that a pregnant woman contracting a viral illness may have a child with a greater risk of developing schizophrenia. (However, maternal viral infections probably account for only a small fraction of the increased risk of schizophrenia.) Additional environmental factors that can complicate illness include stress, particularly the stress of adolescence.

Source: Reprinted by permission of the author. From Gottesman, I.I., Schizophrenia Genesis: The Origins of Madness, New York: W.H. Freeman, 1991, p.96 (c) 1991 Irving I. Gottesman.
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