The odds of developing schizophrenia are approximately 1 in 100 in the general population; 1 in 10 if a family member has it; and 1 in 2 if an identical twin has the disorder. Adoption studies show that an adopted child's chances of developing the disorder are greater if the biological parents have schizophrenia, but not if the adopted parents have it. But 50 percent of those whose identical twins have schizophrenia do not develop the condition themselves, demonstrating that genetics is not the sole cause of this disorder
