Which statement best differentiates delusional disorder from schizophrenia?

• A. Delusional disorder features persistent delusions for at least one month with relative absence of prominent hallucinations or disorganized thinking
• B. Hallucinations are required for diagnosis
• C. Disorganized speech is required for diagnosis
• D. Negative symptoms must be present

Answer: (B)

Differentiating delusional disorder from schizophrenia hinges on how widespread and prominent psychotic symptoms are beyond the fixed delusions. In delusional disorder, there are one or more delusions lasting at least a month, but functioning is not markedly impaired and there are no prominent hallucinations or disorganized thinking. The delusions tend to be isolated and theme-specific, not accompanied by the broader psychotic picture.

In schizophrenia, by contrast, you need multiple symptoms from a core set (delusions, hallucinations, disorganized speech, grossly disorganized or negative symptoms) present for a significant portion of time, with at least one of the symptoms being delusions, hallucinations, or disorganized speech. Hallucinations can occur, but they are not required for a schizophrenia diagnosis; you can have schizophrenia with prominent delusions and disorganized speech and minimal or even absent hallucinations.

Thus the best differentiating point is that delusional disorder centers on persistent delusions with relatively preserved overall functioning and little to no prominent hallucinations or disorganized thinking, whereas schizophrenia involves a broader psychotic syndrome, often with hallucinations and disorganized speech, in addition to delusions.