A 17-year-old boy is diagnosed with schizophrenia. What is the risk that one of his siblings will develop the disease?

The risk of developing schizophrenia in first degree relatives of schizophrenic patients is elevated compared to the risk of the general population (0.9%). Parents of schizophrenic patients have a lifetime prevalence of 11%, and siblings have a prevalence of 9%. Identical twins have a 50% chance of suffering from schizophrenia if their sibling has it. Children of schizophrenics have a lifetime prevalence of 12.8%. Reference: Kaplon and sadock, 11 th edition, synopsis of psychiatry, 11 th edition, pg no. 310