| Capgras delusion | |
|---|---|
| Classification and external resources | |
| DiseasesDB | 32606 |
The Capgras delusion theory (or Capgras syndrome) is a disorder in which a person holds a delusion that a friend, spouse, parent, or other close family member has been replaced by an identical-looking impostor. The Capgras delusion is classified as a delusional misidentification syndrome, a class of delusional beliefs that involves the misidentification of people, places, or objects. It can occur in acute, transient, or chronic forms. Cases in which patients hold the belief that time has been "warped" or "substituted" have also been reported.[1]
The delusion is most common in patients diagnosed with schizophrenia, although it can occur in connection with a number of conditions, including brain injury and dementia.[2] It has also been reported as occuring in association with diabetes, hypothyroidism and migraine attacks.[3] It occurs more frequently in females, with a female:male ratio of 3:2.[4] Although the Capgras delusion is commonly called a syndrome, because it can occur as part of, or alongside, various other disorders and conditions, some researchers have argued that it should be considered a symptom, rather than a syndrome or classification in its own right.
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The Capgras delusion is named after Joseph Capgras (1873–1950), a French psychiatrist who first described the disorder in 1923 in his paper co-authored by Reboul-Lachaux,[5] on the case of a French woman who complained that corresponding "doubles" had taken the places of her husband and other people she knew.
Their term l'illusion des « sosies »...—which can be literally translated as "the illusion of 'doubles'..."—finds some[6] modern professional use in French (e.g. "L’illusion des sosies de Capgras est...", which however its authors render in English as "Capgras’[7] syndrome is ...").[8] But the distinction between illusion and delusion is important in modern technical English, and the Capgras syndrome is clearly a delusional condition.
This case is taken from a 1991 report by Passer and Warnock:[9]
Mrs. D, a 74-year-old married housewife, recently discharged from a local hospital after her first psychiatric admission, presented to our facility for a second opinion. At the time of her admission earlier in the year, she had received the diagnosis of atypical psychosis because of her belief that her husband had been replaced by another unrelated man. She refused to sleep with the impostor, locked her bedroom and door at night, asked her son for a gun, and finally fought with the police when attempts were made to hospitalise her. At times she believed her husband was her long deceased father. She easily recognised other family members and would misidentify her husband only.
Some of the first clues to the possible causes of the Capgras delusion were suggested by the study of brain-injured patients who had developed prosopagnosia. In this condition, patients are unable to recognize faces consciously, despite being able to recognize other types of visual objects. However, a 1984 study by Bauer showed that even though conscious face recognition was impaired, patients with the condition showed autonomic arousal (measured by a galvanic skin response measure) to familiar faces,[10] suggesting that there are two pathways to face recognition—one conscious and one unconscious.
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" of prosopagnosia, in that their conscious ability to recognize faces was intact, but they might have damage to the system that produces the automatic emotional arousal to familiar faces.[11] This might lead to the experience of recognizing someone while feeling something was not "quite right" about them.
In 1997, Hadyn 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.[12]
In 1997, William Hirstein and Vilayanur S. Ramachandran reported similar findings in a paper published on a single case of a patient with Capgras delusion after brain injury.[13] Ramachandran also portrays this case in his book Phantoms in the Brain.[14] Ramachandran also gave a talk about it at TED 2007 video can be found here Since the patient was capable of feeling emotions and recognizing faces but could not feel emotions when recognizing familiar faces, Ramachandran hypothesizes that the origin of Capgras syndrome is a disconnection between the temporal cortex, where faces are usually recognized (see temporal lobe), and the limbic system, involved in emotions. Because the patient could not put together memories and feelings, he believed objects in a photograph were new on every viewing, even though they normally should have evoked feelings (e.g., a person close to him, a familiar object, or even himself). Ramachandran therefore believed there was a relationship between Capgras syndrome and a more general difficulty in linking successive episodic memories, since it is believed that emotion is critical for creating memories.
Most likely, more than an impairment of the automatic emotional arousal response is necessary to form Capgras delusion, as the same pattern has been reported in patients showing no signs of delusions.[15] Ellis and colleagues suggested that a second factor explains why this unusual experience is transformed into a delusional belief; this second factor is thought to be an impairment in reasoning, although no definitive impairment has been found to explain all cases.[16]