My sister(25 years old) thinks that Nazis want to kill her. Is that a bizarre delusion or not?
Delusions are false beliefs. However, in psychiatric a distinction is made between non-bizarre and bizarre delusions. Non-bizarre delusions are within the realms of possibility, such as believing that Nazis are trying to kill a person. This is within the realm of possibility in our society but for most people almost certainly untrue. On the other hand, bizarre delusions are false beliefs that are beyond any possibility of being true, such as a belief that a person is transported nightly to another galaxy. This distinction comes up in the diagnosis of schizophrenia. Among the criteria needed for a diagnosis of schizophrenia, a person needs to have 2 of 5 types of symptoms for a period of time, of which one symptom can be delusions. However, if a person has delusions and they are bizarre, then no other symptom criteria are needed. Many people with a diagnosis of schizophrenia have 2 or more criteria, such as hallucinations and delusions and in those cases the diagnosis is usually fairly straightforward. In the situation where a person has no other criteria than a delusion, then the quality of that delusion can determine whether the diagnosis of schizophrenia is met. If this question was asked to determine whether or not your sister has schizophrenia, it would be important to try to speak with the psychiatrist who could help provide more information about how a diagnosis of schizophrenia is determined. There are other criteria relating to social and functional decline, duration of illness, ruling out other potential causes of the symptoms that must also be considered. Sometimes a definite diagnosis cannot be made, however, this does not mean that treatment is necessarily different and it often depends on the severity of the symptoms.