Schizophrenia is a serious mental illness. It is a long-lasting and disabling problem of the brain. A child with this disorder has unusual behavior and strange feelings. He or she may suddenly start to have psychotic symptoms. Psychotic means having strange ideas, thoughts, or feelings that are not based in reality. Schizophrenia is not often found in children younger than age 12. It's also hard to spot in the early stages. Often, the psychotic symptoms start in the middle to late teen years. Slightly more boys develop it in childhood. But by the teen years it affects both boys and girls equally.