Delusion of doubles is seen in:

Delusion of doubles, is also known as Capgras syndrome and is usually seen in patients with Schizophrenia. It can be also be seen in patients with the delusional disorder, although is less common. DELUSIONAL MISIDENTIFICATION SYNDROME: Capgras' Syndrome In this, the patient believes that a person, usually closely related to him, has been replaced by an exact double. Eg: A patient stas hitting his wife telling that she is not his wife but she is a nurse and she wants to kill him. Fregoli's Syndrome Here the patient believes that an unfamiliar person has been replaced by a familiar person. Syndrome of Intermetamorphosis Here the patient believes that one or more individuals have been transformed, both physically and psychologically, into another person or people OR that people have exchanged identities with each other Syndrome of Subjective Doubles In this syndrome, the patient has the delusion that another person has been physically transformed into his own self, like a doppelganger