Delusional Disorder is a mental illness associated with one or more delusions of thinking—such as expressing beliefs that occur in real life such as being poisoned, being stalked, being loved or deceived, or having an illness, provided no other symptoms of schizophrenia are exhibited.
Delusions may seem believable at face value, and patients may appear normal as long as an outsider does not touch upon their delusional themes. Mood episodes are relatively brief compared with the total duration of the delusional periods. Also, these delusions are not due to a medical condition or substance abuse.
The fraudulent artist Walter Keane was a famous sufferer of delusional disorder.
When the delusion is shared with other people, it is called “shared delusional disorder” or Folie à deux.
Query whether it is a form of delusional disorder for a Male to believe that he is Female (this is a separate question from a Male who understands he is Male, but wishes to live socially as a Woman, i.e., transsexualism).
Structure of the psychotic disorders classification in DSM 5 Margaret Keane’s Artful Case Proves That She—and Not Her Ex-Husband—made Waifs _ People Delusional Disorder _ Psychology Today The big-eyed children_ the extraordinary story of an epic art fraud _ Art and design _ The Guardian