The short answer is this: a person is 11 times more likely to develop schizophrenia if he or she has a relative with the disorder. It’s important to understand what this number means. Many studies show that schizophrenia occurs in 0.2 to 1.1% of people who have no relatives with schizophrenia. People who have a relative with the disorder get it at a rate of 1.4 to 16.2%. In identical twins, if one sibling has schizophrenia, the other has a 31- 78% chance of having the disease. These...