Overview What is delusional disorder? Delusional disorder is a type of psychotic disorder. Its main symptom is the presence of one or more delusions. A delusion is an unshakable belief in something that’s untrue. The belief isn’t a part of the person’s culture or subculture, and almost everyone else knows this belief to be false.

stroke substance use or withdrawal Knowing the underlying causes of hallucinations and/or delusions is important, since an accurate diagnosis will help guide treatment. What are hallucinations?.