Like schizophrenia, delusional disorder is characterized by the presence of delusions that persist for at least one month, and which often involve prominent psychotic themes: erotomanic, grandiose, jealous, persecutory, and/or somatic. Unlike schizophrenia, however, hallucinations are not prominent, unless related to the delusions. Delusional disorder also tends to start later in life than schizophrenia, and tends to leave patients' psychosocial functioning (their ability to care for themselves, work, have relationships, etc.) relatively unimpaired (See the section above covering delusional types for more detail).
The following diagnostic criteria must be met before a diagnosis of Delusional Disorder is warranted, according to the DSM-IV-TR:
A) Non bizarre delusions (i.e., involving situations that occur in real life, such as being followed, poisoned, infected, loved at a distance, or deceived by spouse or lover, or having a disease) of at least 1 month's duration.
B) Criterion A for Schizophrenia has never been met.
C) Apart from the impact of the delusion(s) or its ramifications, functioning is not markedly impaired and behavior is not obviously odd or bizarre
D) If mood episodes have occurred concurrently with delusions, their total duration has been brief relative to the duration of the delusional periods
E) The disturbance is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition