Further, it indicates that many factors influence the eventual outcomes for persons with schizophrenia. Because all four genetically identical women suffered a schizophrenic break within a short period of time, it seems clear that they had inherited or acquired a predisposition, or vulnerability, for schizophrenia. Yet, many years later, they had achieved very different levels of adjustment, indicating that factors other than heredity were also important. The symptoms necessary for a diagnosis of schizophrenia are described on page 450. Students often confuse delusions with hallucinations.
Delusions involve faulty thinking, and hallucinations involve faulty perceptions.
In other cases, the delusions and hallucinations seem unrelated. The DSM-IV does not allow the diagnosis of schizophrenia to be made unless symptoms have persisted for at least six months. If the disorder has been present for less than six months, the diagnosis of schizophreniform disorder is used. There are some indications that the undifferentiated type may be a transitional stage, and the person may go on to develop one of the more specific types of schizophrenia. In other cases, the person never meets criteria for anything but undifferentiated schizophrenia.