Schizophrenia seems to be caused by a mixture of environmental factors and genetics. Having a “faulty” gene might increase your chance of getting schizophrenia, but so can smoking cannabis, or your mother suffering form the flu while she was pregnant with you and various other things. Even living in a city or being born in the winter can give you a slightly increased chance of suffering from schizophrenia (although it is very slight).
It is possible that your genes determine whether you are “at risk” of getting schizophrenia, but that it takes environmental factors to “trigger it”.
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