Delusional Disorder
Delusional disorder refers to a condition in which an individual displays one or more delusions for one month or longer. Delusional disorder is distinct from schizophrenia and cannot be diagnosed if a person meets the criteria for schizophrenia. If a person has delusional disorder, functioning is generally not impaired and behavior is not obviously odd, with the exception of the delusion. Delusions may seem believable at face value, and patients may appear normal as long as an outsider does not touch upon their delusional themes.
Diagnostic Criteria
A. The presence of one (or more) delusions with a duration of 1 month or longer.
B. Criterion A for schizophrenia has never been met.
Note: Hallucinations, if present, are not prominent and are related to the delusional theme (e.g., the sensation of being infested with insects associated with delusions of infestation).
C. Apart from the impact of the delusion(s) or its ramifications, functioning is not markedly impaired, and behavior is not obviously bizarre or odd.
D. If manic or major depressive episodes have occurred, these have been brief relative to the duration of the delusional periods.
E. The disturbance is not attributable to the physiological effects of a substance or another medical condition and is not better explained by another mental disorder, such as body dysmorphic disorder or obsessive-compulsive disorder.