It is an illness that strikes 1 percent of Americans, or about 2.4 million men and women, yet few people have a clear understanding of what schizophrenia is, and what can be done to help those who have it. Even expert thinking about schizophrenia is changing. Many doctors and researchers now believe it is a group of mental illnesses rather than just one. Although genetics affect who is mostly likely to develop schizophrenia, environmental factors also play a role, and the causes and triggers of the condition are not completely clear. How much do you know about schizophrenia? Test your knowledge with the following questions. The answers may surprise you.