Delusional misidentification syndromes:Share the theme of doubles (ie, duplication of self, others, or the environment). They are associated with impairments in facial processing and are closely related to and sometimes co-occur with reduplicative paramnesia.
- Delusional hypoidentification (eg, Capgras syndrome)
- Delusional hyperidentification (eg, Frégoli, intermetamorphosis, subjective doubles syndromes)
- Obsessive-compulsive disorder: A person who remains convinced that his/her obsessions and compulsions are true convictions, should be given the diagnosis of obsessive-compulsive disorder with absent insight.
- Schizophrenia spectrum disorders: Can be differentiated from delusional disorder by the presence of other symptoms of the active phase of schizophrenia.
- Delirium/major neurocognitive disorder: Can mimic delusional disorder but distinguished based on the chronology of symptoms.
- Depression or bipolar disorder: Delusions occur with mood episodes. A delusional disorder is diagnosed only when the span of delusions exceed the total duration of mood symptoms.