Delusional misidentification syndrome

Template:Short description Template:Infobox medical condition (new) Delusional misidentification syndrome is an umbrella term, introduced by Christodoulou (in his book The Delusional Misidentification Syndromes, Karger, Basel, 1986) for a group of four delusional disorders that occur in the context of mental and neurological illness. They are grouped together as they often occur simultaneously or interchange, and they display the common concept of the double (sosie).<ref>Template:Cite journal</ref> They all involve a belief that the identity of a person, object, or place has somehow changed or has been altered. Christodoulu further categorized these disorders into those including hypo (or under)-identification of a well-known person (Capgras delusion), and hyper (or over)-identification of an unknown person (the remaining three).<ref name=":0">Template:Cite book</ref> As these delusions typically only concern one particular topic, they also fall under the category called monothematic delusions.<ref>Template:Cite book</ref>

Variants

This psychopathological syndrome is usually considered to include four main variants:<ref>Template:Cite journal</ref><ref name=":0" />

• The Capgras delusion is the belief that (usually) a close relative or spouse has been replaced by an identical-looking impostor.
• The Fregoli delusion is the belief that various people the believer meets are actually the same person in disguise.
• Intermetamorphosis is the belief that an individual has the ability to take the form of another person in both external appearance and internal personality.
• Subjective doubles, described by Christodoulou in 1978 (American Journal of Psychiatry 135, 249, 1978), is the belief that there is a doppelgänger or double of themselves carrying out independent actions.<ref>Christodoulou G.N. Delusional Misidentification Syndromes, Karger, Basel, 1986</ref><ref>Christodoulou G.N. The Syndrome of Capgras, Br. J. Psychiatry 130, 556, 1977</ref><ref>Christodoulou G.N. Syndrome of Subjective Doubles, Am. J. Psychiat.135,249,1978</ref>

However, similar delusional beliefs, often singularly or more rarely reported, are sometimes also considered to be part of the delusional misidentification syndrome. For example:

• Mirrored-self misidentification is the belief that one's reflection in a mirror is some other person.
• Reduplicative paramnesia is the belief that a familiar person, place, object, or body part has been duplicated. For example, a person may believe that they are in fact not in the hospital to which they were admitted, but an identical-looking hospital in a different part of the country.<ref>Template:Cite journal</ref>
• Cotard's syndrome is a rare disorder in which people hold a delusional belief that they are dead (either figuratively or literally), do not exist, are putrefying, or have lost their blood or internal organs. In rare instances, it can include delusions of immortality.<ref>Template:Cite journal</ref>
• Syndrome of delusional companions is the belief that objects (such as soft toys) are sentient beings.<ref>Template:Cite journal</ref>
• Clonal pluralization of the self, where a person believes there are multiple copies of themselves, identical both physically and psychologically, but physically separate and distinct.<ref>Template:Cite journal</ref>
• Clinical lycanthropy is the belief that one is turning or has turned into an animal. It is considered a delusional misidentification of the self.<ref>Template:Cite journal</ref>

There is considerable evidence that disorders such as the Capgras or Fregoli syndromes are associated with disorders of face perception and recognition. However, it has been suggested that all misidentification problems exist on a continuum of anomalies of familiarity,<ref>Template:Cite journal</ref> from déjà vu at one end to the formation of delusional beliefs at the other.

See also

• Prosopagnosia
• Cognitive neuropsychiatry
• Crisis actor conspiracy theory
• Implicit memory
• The Truman Show delusion