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Psychotic symptoms include hallucinations, delusions (fixed false beliefs, such as the belief that aliens have taken over one’s body and are controlling one’s thoughts and actions), and disorganized thinking (as demonstrated by illogical or incoherent speech) or behavior. In chronic form, these symptoms are most commonly associated with schizophrenia spectrum disorders, but they can occur in the context of many other illnesses, including major depression or bipolar disorder, substance intoxication or withdrawal, borderline personality disorder, and a wide range of other medical conditions, including neurodegenerative, infectious, inflammatory, and autoimmune diseases (Table 31-1).

Table 31-1.Differential diagnosis of new onset psychosis.


The schizophrenia spectrum disorders include brief psychotic disorder, schizophreniform disorder, schizophrenia, schizoaffective disorder, and delusional disorder. They are distinguished from each other by the duration and types of psychotic symptoms, and the presence or absence of concurrent mood symptoms.

The onset of multiple types of psychotic symptoms (delusions, hallucinations, disorganized speech or behavior) in the absence of affective symptoms, a toxic exposure, or an associated medical condition defines brief psychotic disorder if it lasts less than a month, schizophreniform disorder if it lasts 1–6 months, and schizophrenia if it lasts at least 6 months. Schizophrenia tends to begin in late adolescence or early adulthood and affects between 0.3% and 0.9% of the population worldwide. Schizoaffective disorder requires the presence of multiple psychotic symptoms in addition to recurrent episodes of major depression or mania. It also commonly starts in adolescence or young ...

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