Schizophrenia is a type of psychotic disorder (severe mental condition that causes the patient to lose touch with reality). People may develop schizophrenia alone, or it may occur in combination with other psychiatric or medical conditions.

This is only one of a number of illnesses that include psychotic symptoms. Losing touch with reality or having abnormal thoughts does not mean that someone has schizophrenia, and schizophrenia is not the same thing as a split personality, as some people believe because of the origin of the word "schizophrenia."

Schizophrenia can be diagnosed at any age, but 75 percent of people with the disorder first develop symptoms between the ages of 16 and 25 years, according to the National Alliance on Mental Illness (NAMI). Schizophrenia rarely occurs before puberty, although cases in children as young as 5 years old have been reported. The illness is difficult to recognize in children and adolescents because hallucinations, the hallmark of schizophrenia, can be caused by a number of other unrelated conditions, and because its slow onset can lead to an assumption that it is a behavior problem.

About 1 percent of the U.S. population develops schizophrenia, according to NAMI. The illness affects men and women equally, although it often appears at an earlier age in males than females. Onset in males typically occurs between the late teens and early 20s. In females, onset usually occurs between the 20s or early 30s.

Schizophrenia may be related to development of a child's brain during pregnancy. One theory is that changes before birth lead to faulty connections within the brain. These poor connections are dormant until puberty, when the brain undergoes dramatic changes, which can lead to the psychotic symptoms associated with the condition. There is, however, no direct scientific evidence that leads scientists and doctors to believe that there is a single cause for this illness.

The structure of the brain appears different in some patients as compared to the general population. Some of these differences include the following:

• The fluid-filled cavities at the center of the brain (ventricles) are larger.
  
  
• The volume of gray matter (which consists of the neurons, brain cells) is lower.
  
  
• Some areas of the brain have abnormal metabolic activity.

It is important to note that not all patients with schizophrenia have these differences. Nor do all patients with these differences have schizophrenia.