Schizophrenia has both genetic and environmental etiologies.. As per studies if single parent is affected then there are 12% chances that the offspring may have schizophrenia.. Genetics and genetic mutations play an important role in the cause of many mental illnesses. What exactly that role is and the extent to which a certain mutation results in a greater risk factor varies widely. We simply do not yet know exactly what causes mental illnesses like schizophrenia.