Delusional misidentification syndrome

Delusional misidentification syndrome is an umbrella term, introduced by Christodoulou (in his book The Delusional Misidentification Syndromes, Karger, Basel, 1986) for a group of delusional disorders that occur in the context of mental or neurological illness. They all involve a belief that the identity of a person, object, or place has somehow changed or has been altered. As these delusions typically only concern one particular topic, they also fall under the category called monothematic delusions.

This syndrome is usually considered to include four main variants:^[1]

• The Capgras delusion is the belief that (usually) a close relative or spouse has been replaced by an identical-looking impostor.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 people in the environment swap identities with each other whilst maintaining the same appearance.
• 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 him- or herself carrying out independent actions.^[2][3][4]

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, despite this being obviously false.^[5]
• The Cotard delusion 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.^[6]
• Syndrome of delusional companions is the belief that objects (such as soft toys) are sentient beings.^[7]
• Clonal pluralization of the self, where a person believes there are multiple copies of him- or herself, identical both physically and psychologically but physically separate and distinct.^[8]

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,^[9] from déjà vu at one end to the formation of delusional beliefs at the other.

See also

• Cognitive neuropsychiatry
• Implicit memory

References

1. Ellis HD, Luauté JP, Retterstøl N (1994). "Delusional misidentification syndromes". Psychopathology 27 (3-5): 117–20. doi:10.1159/000284856. PMID 7846223.
2. Christodoulou G.N. Delusional Misidentification Syndromes, Karger, Basel, 1986
3. Christodoulou G.N. The Syndrome of Capgras, Brit. J. Psychiat.130, 556, 1977
4. Christodoulou G.N. Syndrome of Subjective Doubles, Am. J. Psychiat.135,249,1978
5. Benson DF, Gardner H, Meadows JC (February 1976). "Reduplicative paramnesia". Neurology 26 (2): 147–51. doi:10.1212/wnl.26.2.147. PMID 943070.
6. Berrios G.E., Luque R. (1995). "Cotard Syndrome: clinical analysis of 100 cases". Acta Psychiatrica Scandinavica 91 (3): 185–188. doi:10.1111/j.1600-0447.1995.tb09764.x. PMID 7625193.
7. Shanks MF, Venneri A (November 2002). "The emergence of delusional companions in Alzheimer's disease: an unusual misidentification syndrome". Cogn Neuropsychiatry 7 (4): 317–28. doi:10.1080/13546800244000021. PMID 16571545.
8. Vörös V, Tényi T, Simon M, Trixler M (2003). "'Clonal pluralization of the self': a new form of delusional misidentification syndrome". Psychopathology 36 (1): 46–8. doi:10.1159/000069656. PMID 12679592.
9. Sno HN (1994). "A continuum of misidentification symptoms". Psychopathology 27 (3-5): 144–7. doi:10.1159/000284861. PMID 7846229.