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Capgras delusion or Capgras syndrome (CS) is a psychiatric disorder in which a person holds a delusion that a friend, spouse, parent, other close family member, or pet has been replaced by an identical impostor.

It is named after Joseph Capgras (1873–1950), the French psychiatrist who first described the disorder. The Capgras delusion is classified as a delusional misidentification syndrome, a class of beliefs that involves the misidentification of people, places, or objects. Cases in which patients hold the belief that time has been "warped" or "substituted" have also been reported. The delusion most commonly occurs in individuals diagnosed with a psychotic disorder, usually schizophrenia; it has also been seen in brain injury, dementia with Lewy bodies, and other forms of dementia. In one isolated case, the Capgras delusion was temporarily induced in a healthy subject by administration of ketamine.

Capgras syndrome is named after Joseph Capgras, a French psychiatrist who first described the disorder in 1923 in his paper co-authored by Jean Reboul-Lachaux. Today, Capgras syndrome is understood to primarily result from neurodegenerative diseases and neurological damage, and is less commonly caused by psychotic disorders.

The prevalence of Capgras delusion (CS) in psychiatric populations (e.g., individuals with existing mental illnesses) ranges from less than 1% to 4.1%.

It is generally agreed that the Capgras delusion has a complex and organic basis and can be better understood by examining neuroanatomical damage associated with the syndrome. In one of the first papers to consider the cerebral basis of the Capgras delusion, Alexander, Stuss and Benson pointed out in 1979 that the disorder might be related to a combination of frontal lobe damage causing problems with familiarity and right hemisphere damage causing problems with visual recognition. Further clues to the possible causes of the Capgras delusion were suggested by the study of brain-injured patients who had developed prosopagnosia. In a 1990 paper published in the British Journal of Psychiatry, psychologists Hadyn Ellis and Andy Young hypothesized that patients with Capgras delusion may have a "mirror image" or double dissociation of prosopagnosia, in that their conscious ability to recognize faces was intact, but they might have damage to the system which produces the automatic emotional arousal to familiar faces. In 1997, Ellis and his colleagues published a study of five patients with Capgras delusion (all diagnosed with schizophrenia) and confirmed that although they could consciously recognize the faces, they did not show the normal automatic emotional arousal response. A patient with Capgras delusion showed reduced GSRs to faces in spite of normal face recognition. This theory for the causes of Capgras delusion was summarised in Trends in Cognitive Sciences in 2001. Ramachandran reported similar findings in a paper published on a single case of a patient with Capgras delusion after brain injury. They suggest that an important and familiar person (the usual subject of the delusion) has many layers of visual, auditory, tactile, and experiential memories associated with them, so the Capgras delusion can be understood as a failure of object constancy at a high perceptual level. Most likely, more than a mere impairment of the automatic emotional arousal response is necessary to form the Capgras delusion, as the same pattern has been reported in patients showing no signs of delusions. The authors of this 2022 case study referred to recreational drug use triggered Capgras syndrome as being an extremely rare condition with infrequent documentation which therefore requires first ruling out other potential triggers and direct causes associated with Capgras syndrome.

Because it is a rare and poorly understood condition, there is no established way to diagnose the Capgras delusion.

Treatment of Capgras delusion has not been well studied, so there is no evidence-based approach. As manifestation of Capgras delusion is often a symptom rather than a syndrome itself, treatment may focus on the accompanying condition.

Quick Facts

• The Capgras delusion is classified as a delusional misidentification syndrome, a class of beliefs that involves the misidentification of people, places, or objects.
• Capgras syndrome is named after Joseph Capgras, a French psychiatrist who first described the disorder in 1923 in his paper co-authored by Jean Reboul-Lachaux.
• The delusion most commonly occurs in individuals diagnosed with a psychotic disorder, usually schizophrenia; it has also been seen in brain injury, dementia with Lewy bodies, and other forms of dementia.
• It is named after Joseph Capgras (1873–1950), the French psychiatrist who first described the disorder.
• In one isolated case, the Capgras delusion was temporarily induced in a healthy subject by administration of ketamine.

Source material: Wikipedia - "Capgras delusion". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.