context: Schizophrenia usually takes hold after puberty. Most people are diagnosed in their late teens to early 30s. Men and women are equally likely to get this brain disorder, but guys tend to get it slightly earlier. On average, men are diagnosed in their late teens to early 20s. Women tend to get diagnosed in their late 20s to early 30s. People rarely develop schizophrenia before they're 12 or after they're 40. An interaction between something in your genes and something in your environment probably causes the disease. Researchers still have a lot to learn about it, but it's likely that many things play a role. Some, like exposure to a virus or malnutrition (according to one theory about causes), might have happened while you were still in your mother's womb. No one knows exactly why it usually crops up in late adolescence, but there are many theories. Your brain changes and develops a lot during puberty. These shifts might trigger the disease in people who are at risk for it. Some scientists believe it has to do with development in an area of the brain called the frontal cortex. Others think it has to do with too many connections between nerve cells being eliminated as the brain matures. Hormones also play a major role in puberty. One theory is that women get schizophrenia later than men because they go through puberty earlier and the hormone estrogen might somehow protect them. Schizophrenia can be hard to diagnose for a few reasons. One is that people with the disorder often don't realize they're ill, so they're unlikely to go to a doctor for help. Another issue is that many of the changes leading up to schizophrenia, called the prodome, can mirror other normal life changes. For example, a teen who's developing the illness might drop his group of friends and take up with new ones. He may also have trouble sleeping or suddenly start coming home with poor grades. Some research suggests that if a doctor strongly thinks someone is getting the disorder while still in this early phase, low doses of antipsychotic medication might delay it. More studies need to be done to know whether these drugs work for young people at risk for the disease. Cognitive behavioral therapy, family therapy, and social skills training appear to have clearer benefits for them, at least in the short term, when used early on. About 3.5 million people in the United States are diagnosed with schizophrenia. It affects about 1.1% of the world's population. Once you have full-blown schizophrenia, the symptoms are much more severe. They include: Hallucinations . You hear voices or see or smell things that others say aren't there. The voices might criticize or threaten you. They might tell you to do things you otherwise wouldn't. Delusions. You believe things that aren't true, even when others show you proof or share facts that explain why your beliefs are wrong. Delusions can seem bizarre to others. For example, you might think that the TV is sending you special messages or that the radio is broadcasting your thoughts for everyone to hear. You might also feel paranoid and believe that others are trying to harm you. Thought disorders. You might have trouble organizing your thoughts, and you might speak in a way that's hard for others to understand. Perhaps you stop talking in the middle of a thought because you feel like it's been taken out of your head. This is called thought withdrawal. Another type of disordered thinking, called thought blocking, happens when someone has a sudden stopping of their flow of thinking and as a consequence they may become silent until a new thought enters their mind. Movement disorders. You might move your body over and over again as if you're upset, or you might stop moving and responding. Doctors call this catatonia. Negative symptoms. Maybe you speak in a dull, flat tone, have trouble following through, lack interest in your daily life, and find it hard to keep up relationships. You might appear to be depressed. But while sadness, tearfulness, and other symptoms point to depression, so-called negative symptoms more likely point to a problem with the way the brain works. Schizophrenia can develop later in life. Late-onset schizophrenia is diagnosed after the person is 45. People who have it are more likely to have symptoms like delusions and hallucinations. They're less like to have negative symptoms, disorganized thoughts, impaired learning, or trouble understanding information. Doctors think genetics may be to blame, just as it is with early-onset schizophrenia. They also think late onset might be a subtype that doesn't affect the person until the right trigger appears. People with cognitive, vision, or hearing problems, or those who are suspicious, isolated, or reclusive may be more likely to get it. It's rare for someone younger than 13 to be diagnosed with schizophrenia, but it can happen. In young children, early-onset schizophrenia often causes: Talking delays Late or unusual crawling Late walking Unusual movements like arm flapping or rocking Parents of teens might notice: Not spending as much time with friends and family Drop in school performance Trouble sleeping Bad mood Depression No motivation Using drugs or alcohol Odd behavior Teens are less likely to have delusions but more likely to have visual hallucinations.