What Are Delusions?

Delusions are beliefs or ideas that are thoroughly believed to be true, despite being demonstrably false. Often, delusions are symptoms of mental disorders, such as schizophrenia and bipolar disorder. A person with a delusion cannot be convinced that his or her false belief is not true.

Delusions are symptoms of several psychotic disorders: schizophrenia, schizoaffective disorder, delusional
disorder, disorder, shared psychotic disorder, brief psychotic disorder, substance-induced psychotic disorder, bipolar disorder, and depression with psychosis. Delusions are also present in some people who have Alzheimer’s disease
or dementia.

Delusions may also represent a decline in a person with Parkinson’s condition (though they are rare).