In their bookDivided Minds, identical twins Carolyn Spiro and Pamela Spiro Wagner describe a close childhood relationship, apart from typical sibling rivalries. Carolyn often felt she had to prove that she was as intelligent and creative as Pamela. As they entered their teenage years, however, the twins grew apart. Pamela's increasingly bizarre behaviors became an embarrassment to Carolyn. By the time the twins were college students at Brown University, Pamela was becoming more and more reclusive. Eventually, Pamela had a psychotic episode, although it was years before she was diagnosed with paranoid schizophrenia. Carolyn went on to graduate from Brown and then from Harvard Medical School. She is now a practicing psychiatrist. Pamela lives nearby, doing her artwork when she can but constantly battling to keep her schizophrenia under control with medications and therapy. The twins once again are very close emotionally.

Given what you have learned about the causes of schizophrenia, how might you explain why Pamela developed schizophrenia but Carolyn did not?