Delirium, major neurocognitive disorder, psychotic disorder due to another medical con-
dition, and substance/medicati on-induced psychotic disorder. Individuals with these
disorders may present with symptoms that su ggest delusional disorder. For example, sim-
ple persecutory delusions in the context of major neurocognitive di sorder would be di-
agnosed as major neurocognitive  disorder, with behavioral  disturbance. A substance/
medication-induced psychotic disorder cross-sectionally may be identical in symptom-
atology to delusional disorder but can be di stinguished by the chronological relationship
of substance use to the onset and remission of the delusional beliefs.
Schizophrenia and schizophreniform disorder. Delusional disorder can be distinguished
from schizophrenia and schizophreniform disord er by the absence of the other character-
istic symptoms of the active phase of schizophrenia. 
Depressive and bipolar disorders and schizoaffective disorder. These disorders may
be distinguished from delusional disorder by  the temporal relationship between the mood
disturbance and the delusions and by the severi ty of the mood symptoms. If delusions oc-
cur exclusively during mood episodes, the diag nosis is depressive or  bipolar disorder with
psychotic features. Mood sympto ms that meet full criteria for a mood episode can be su-
perimposed on delusional disorder. Delusional di sorder can be diagnose d only if the total
duration of all mood episodes remains brief rela tive to the total duration of the delusional
disturbance. If not, then a diagnosis of othe r specified or unspecified schizophrenia spec-
trum and other psychotic diso rder accompanied by other sp ecified depressi ve disorder,
unspecified depressive disorder, other specif ied bipolar and related disorder, or unspeci-