Delusions are fixed false beliefs or ideas. They commonly take one of two forms: grandiose or paranoid. In the grandiose type, the patient may think he or she is a god or president of a country. People with schizophrenia have the paranoid type of delusions.
In delusional disorder, a person has a variety of paranoid beliefs, but these beliefs are not bizarre and are not accompanied by any other symptoms of schizophrenia. For example, a person who is functioning well at work but becomes unreasonably convinced that his or her spouse is having an affair has a delusional disorder rather than schizophrenia. Delusional disorder is an illness characterized by at least 1 month of delusions but no other psychotic symptoms.
Delusions, hallucinations, disorganized speech, disorganized or catatonic behavior, or negative symptoms are some of the criteria for diagnosis of schizophrenia. Persons with delusional disorder have a variety of paranoid and delusional beliefs, but none of the psychotic symptoms of schizophrenia.
Difficulty and lack of interest in forming close relationships with others and a preference for solitary activities are typical characteristics of schizoid personality disorder (not delusional disorder). No other symptoms of schizophrenia are present.
A pervasive pattern of discomfort in close relationships with others, along with the presence of odd thoughts and behaviors, are typical characteristics of schizotypal personality disorder (not delusional disorder). The oddness in this disorder is not as extreme as that observed in schizophrenia.
Learn more about schizophrenia differential diagnosis.
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Cite this: Stephen Soreff. Fast Five Quiz: Schizophrenia Differential Diagnosis - Medscape - Aug 11, 2020.