Five hundred and seventy cases in 252 reports of the delusion of substitution yielded 200 cases with an organic contributor to the occurrence of the delusion. In 79 cases lateralization or localization could be determined, with lesions primarily in the left temporal or right frontal areas. Factors related to 'feature recognition', 'familiarity' and 'reduplication' could be found and are discussed in relation to the neurobehavioral features of the symptom.

This detailed clinical report of a typical Capgras delusion (CD) in a demented patient is presented in order to foster future descriptions in neurological cases. In the framework of a recently developed model of familiar person processing, it is suggested that CD might be due to a dysfunction at the level of Person Identity Nodes. Prefrontal impairment is held to represent a critical factor leading to a failure of belief evaluation.

BACKGROUND

A sample of everyday difficulties was collected, encompassing errors and unusual experiences participants had encountered when recognising their own faces in everyday life, with the aim of characterising similarities and differences between the reported difficulties and the major forms of self-recognition impairments described in the neuropsychological and neuropsychiatric literatures (prosopagnosia, mirrored-self misidentification, and Capgras delusion).

METHODS

A total of 70 participants recalled experiences from memory. Incidents (n = 51) were recorded on questionnaire sheets that were filled out at home. Reports of three categories of incidents were analysed: misidentifications (the participant misidentified her/his own face as being that of another familiar person; n = 5), recognition failures (the participant judged that his/her own face was that of an unfamiliar person; n = 20) and perception of unusual aspects (the participant confidently recognised his/her own face but found that the seen face did not fit well the representation she/he had of his/her own face; n = 26).

CONCLUSIONS

In the reported incidents, experiences showing some similarities to those of patients with prosopagnosia, Capgras delusion or mirrored-self misidentification were noted. However, across the whole study, no incident involved a failure of reality testing; in contrast to pathological forms of error, in all of the reported incidents from our study the participant realised that a mistake had been made. The importance of decision processes in pathological forms of own-face misrecognition is discussed.

Following a general review of the literature linking right hemisphere dysfunction to psychoses in general and Capgras delusion (CD) in particular, two studies are described that confirm the link. Study 1 revealed that, compared with matched psychiatric controls, 3 CD patients were particularly poor at matching pairs of faces shown briefly in the left visual field-which implies dysfunctioning right hemisphere performance. However there was no difference in performance when the faces appeared bilaterally, which fails to support the hypothesis that poor interhemispheric communication may give rise to CD. The second study involved tests of face memory and word memory. CD and other delusional misidentification groups scored markedly low on the face test, again implying right hemisphere deficit. Finally, a model of what may be the right hemisphere mechanisms giving rise to CD was explored. This assumes two routes to face recognition, ventral and dorsal. It is argued that exclusive damage to the former may cause prosopagnosia and problems in the latter may give rise to the symptoms of CD.

The psychodynamic explanations for the Capgras delusion are reviewed. A critique is offered, showing how these theories fail to account for several important clinical phenomena found in patients with the Capgras delusion. A new psychodynamic theory is suggested that attempts to encompass all of the significant clinical phenomena. This hypothesis is based on findings in a series of fourteen schizophrenic patients with the typical delusion. The focus is on the patient's loss of a stable sense of identity. By the process of projection the patient ascribes his identity diffusion to those around him who are then seen as unreal impostors.

Capgras syndrome is characterized by a delusion of impostors who are thought to be physically similar but psychologically distinct from the misidentified person. This syndrome is generally thought to be relatively rare. Most of our knowledge about Capgras syndrome derives from single case studies and small series of cases usually from diagnostically heterogeneous groups. In this article, a series of 31 patients suffering from both paranoid schizophrenia and Capgras syndrome is described. Issues pertaining to the phenomenology of Capgras syndrome, the possible relation between Capgras syndrome and other delusional misidentification syndromes, and a neurobiological hypothesis aimed at explaining Capgras syndrome are discussed.

Delusions are explanations of anomalous experiences. A theory of delusion requires an explanation of both the anomalous experience and the apparently irrational explanation generated by the delusional subject. Hence, we require a model of rational belief formation against which the belief formation of delusional subjects can be evaluated.

METHODS

I first describe such a model, distinguishing procedural from pragmatic rationality. Procedural rationality is the use of rules or procedures, deductive or inductive, that produce an inferentially coherent set of propositions. Pragmatic rationality is the use of procedural rationality in context. I then apply the distinction to the explanation of the Capgras and the Cotard delusions. I then argue that delusions are failures of pragmatic rationality. I examine the nature of these failures employing the distinction between performance and competence familiar from Chomskian linguistics.

RESULTS

This approach to the irrationality of delusions reconciles accounts in which the explanation of the anomalous experience exhausts the explanation of delusion, accounts that appeal to further deficits within the reasoning processes of delusional subjects, and accounts that argue that delusions are not beliefs at all. (Respectively, one-stage, two-stage, and expressive accounts.)

CONCLUSIONS

In paradigm cases that concern cognitive neuropsychiatry the irrationality of delusional subjects should be thought of as a performance deficit in pragmatic rationality.

A woman with Capgras and de Clérambault's syndromes transmitted persecutory, erotic, and somatic delusions to her son in a folie à deux. Capgras and de Clérambault's syndromes appear together more commonly than is apparent in the literature. Review of these cases shows a strong association with severe affective disorder.

Co-occurrence of the different types of delusional misidentification syndromes (DMS) implies a common pathogenetic substrate. Until now, theoretical explanations have strained to produce a collective approach, but have been trammeled by the initial definition of the syndromes (Capgras/Fregoli) that originated from the attribution of causal significance to the element of familiarity towards the misidentified object. In this article, we present two cases illustrating the co-occurrence of the syndromes and we attempt to propose a new approach to DMS. We hypothesize that a common potential pathogenetic factor underlying DMS could be a disorder of the sense of uniqueness. The ability to attribute uniqueness to the self and to surrounding people, objects, or places is a principal property of the adaptable mind that acts as a matrix for the identification process. We propose that although the term 'identity' encompasses the concept of uniqueness, this must be accomplished somewhere in a model of semantic processing of identity. Our approach is questioning the current view that this sequential stage is the PIN stage in the functional model of face recognition by Bruce and Young, and we attempt to see the disordered sense of uniqueness within the evolved form of the model of face recognition and delusional misidentification introduced by Ellis and Lewis. We propose that such a disturbance could result in an unstable identification process, vulnerable to discrepancies in perceptual, emotional, or memory input caused by psychotic or organic mental states, thus resulting in a breakdown of the identification process that inevitably leads to a delusion of denial of identity, or to a delusion of 'doubles'.

Hallucinations and paranoid delusions are recognised complications of critical illness. However, the occurrence of Capgras syndrome, in response to critical illness, where patients are convinced that doubles have replaced close family has not been described in the literature. There have been isolated case histories in the literature in response to medical procedures or illness but mostly in patients suffering from schizophrenia. A 42 year old woman was admitted to the intensive care unit (ICU) with pneumonia, following extensive surgery for a squamous cell carcinoma, secondary to Crohns disease. She had no history of previous head injury, cerebro-vascular problems or psychiatric disorder. She reported having memories of all her family, with the exception of her mother, being replaced by aliens while she was on the ICU. The delusion was only diagnosed once it had resolved and the patient was able to talk, and this highlights the difficulty of diagnosing delusions while patients are still intubated and unable to verbalise their concerns. It has been suggested that a defect in the ability to recognise the emotional significance of the face lies at the root of Capgras syndrome.

We report a case of a blind woman, M.N., who experienced the Capgras delusion. She thought that her pet cat had been replaced by a replica which was "ill-intentioned" towards her. M.N.'s case shows that the basis of the Capgras delusion cannot lie exclusively in damage to the visual system. However, testing of M.N.'s auditory recognition abilities revealed a deficit in the recognition of familiar voices. This impairment is consistent with the view that the Capgras delusion may arise in connection with damage to recognition mechanisms, and parallels findings of face processing impairments in sighted Capgras patients.

Psychotic disorders in patients with multiple sclerosis (MS), although reported in the literature, are quite rare. The maniac psychosis is increased in MS patients, especially after steroid use, but a pure paranoid (delusional) state is very uncommon. We report a case of a patient with MS complicated by Capgras' syndrome. This disorder, characterized by misidentification and also known as "illusion of double", was first described by the French psychiatrist Joseph Capgras in 1923. Our patient was a 36-year-old female, with a negative psychiatric history; the diagnosis of MS dated back to the age of 18. Subsequently, after a treatment with high dosage of steroids for optic neuritis, her psychiatric symptoms (delusion of references) began and she was then treated with clozapine. Thereafter she had repeated relapses. Immunomodulatory treatments with beta-interferon first and azathioprine then were stopped for intolerance. She came to our hospital for a new relapse with severe dynamic ataxia. After a treatment with corticosteroids the patient developed a paranoid disorder characterized by persecutory delusion (illusion of double) towards her husband. Treatment with glatiramer acetate and quetiapine improved her neuropsychiatric condition.

Delusional misidentification syndromes are a group of delusional phenomena in which patients misidentify familiar persons, objects, or themselves, believing that they have been replaced or transformed. In 25%-40% of cases, misidentification syndromes have been reported in association with organic illness. We report an acute episode of Capgras-like delusion lasting 8 days, focused on the idea that people were robots with human bodies, in association with an acute urinary infection. To our knowledge, this is the first case report associating urinary tract infection with Capgras-like syndrome. Awareness of the prevalence of delusional misidentification syndromes associated with acute medical illness should promote diligence on the part of clinicians in recognizing this disorder.

During the 1983 year all patient presentations to the University of Miami Psychiatric Emergency Service (PES) at Jackson Memorial Hospital, a large county hospital, were screened by the author through patient rounds and chart review for the presence of the Capgras delusion (strictly defined). Within 4,200 unduplicated patient presentations, 6 cases were determined to have a Capgras delusion: i.e. 0.14% of all PES unduplicated presentations and 0.17% of all PES psychotic unduplicated presentations. These 6 cases are presented. The majority of these patients presented with the chief complaint of violent behavior towards a significant other and had organic factors as contributors to the psychopathology.

In the Capgras syndrome (CS) there is a natural dissociation between recognition and identification and it deserves to be designated as an agnosia of identification. Joseph Capgras who first introduced this concept of agnosia, also suggested that the syndrome might be studied within the framework of 'méconnaissance systématique' (translated here as systématic unawareness), thus anticipating a type of interpretation in which the basis of CS (and other delusional misidentification syndromes) would be a lack of corporeal and/or egocentric space awareness. From two examples, it is suggested that the basic phenomenon of unawareness may be due to sensory deprivation. A particular process of awareness concerning personal objects is hypothesized which would explain the specific delusion of reduplication that occurs when these objects are misidentified.

BACKGROUND

Misidentification phenomena, including the delusion of 'imposters' named after Joseph Capgras, occur in various major psychiatric and neurological disorders but have rarely been studied systematically in broad samples of modern patients. This study investigated the prevalence and correlated clinical factors of Capgras' phenomenon in a broad sample of patient-subjects with first-lifetime episodes of psychotic affective and nonaffective disorders.

METHODS

We evaluated 517 initially hospitalized, first-episode psychotic-disorder patients for the prevalence of Capgras' phenomenon and its association with DSM-IV-TR diagnoses including schizophreniform, brief psychotic, unspecified psychotic, delusional, and schizoaffective disorders, schizophrenia, bipolar-I disorder and major depression with psychotic features, and with characteristics of interest including antecedent psychiatric and neurological morbidity, onset type and presenting psychopathological phenomena, using standard bivariate and multivariate statistical methods.

RESULTS

Capgras' syndrome was identified in 73/517 (14.1%) patients (8.2-50% across diagnoses). Risk was greatest with acute or brief psychotic disorders (schizophreniform psychoses 50%, brief psychoses 34.8%, or unspecified psychoses 23.9%), intermediate in major depression (15%), schizophrenia (11.4%) and delusional disorder (11.1%), and lowest in bipolar-I (10.3%) and schizoaffective disorders (8.2%). Associated were somatosensory, olfactory and tactile hallucinations, Schneiderian (especially delusional perception), and cycloid features including polymorphous psychotic phenomena, rapidly shifting psychomotor and affective symptoms, pananxiety, ecstasy, overconcern with death, and perplexity or confusion, as well as rapid onset, but not sex, age, abuse history, dissociative features, or indications of neurological disorders.

CONCLUSIONS

Capgras' syndrome was prevalent across a broad spectrum of first-episode psychotic disorders, most often in acute psychoses of rapid onset.

BACKGROUND

Anomalous experiences occur in many psychiatric conditions, but are also reported by non-patients. Given the continuum account of psychiatric symptoms and reports of dissociation between delusions and anomalous experiences, we predicted that anomalous experiences in a large non-clinical sample would (1) associate with delusion-like beliefs but not with socio-cultural beliefs and (2) that anomalous experiences would also show examples of dissociation with anomalous beliefs. A particular focus was the association between beliefs and experiences theoretically predicted to co-occur in Capgras syndrome.

METHODS

The study examined the distribution and correlates of differential levels of self-reported anomalous experience in a British sample of 1,000 individuals.

RESULTS

Anomalous experiences were found to be relatively common in the general population and were reported (occurring sometimes/often) by 48% of the sample. Being female and endorsing a non-Christian religion were the only two demographic factors related to higher experience scores. Significant relationships were found between anomalous experiences and anomalous beliefs (i.e., delusion-like and paranormal/religious), but not general societal beliefs. Dissociations between anomalous experiences and anomalous beliefs also were present but not common. No significant relationship was found between Capgras-type beliefs and experiences.

CONCLUSIONS

This large scale study demonstrated significant association between anomalous experiences and anomalous beliefs in the general population. The relationship was not, however present in all cases similar to cases reported in the clinical literature.

The delusional belief that a close relative has been replaced by a look-alike impostor was named the Capgras delusion in honor of Joseph Capgras, who described the first case. Capgras's original patient, Mme M., had a complex mental illness with various symptoms in addition to the delusion of substitution. The focus in the literature has always been on her eponymous delusion, ignoring the rest of her condition. However, studying the substitution delusion in isolation from the rest of her illness has led to inadequate conclusions. It is necessary to understand the delusion within the broad context of her illness. Toward that goal, her mental illness is described here in detail. A particular pattern of delusions and illness is identified. This same pattern is noted in other cases of Capgras in the literature. Three new cases are reported here, each with the same overall pattern of illness that Mme M. had. This pattern is labeled the Syndrome of Capgras. A hypothesis is offered to explain the Capgras delusion within the context of this illness.

Capgras' syndrome, the delusion of substitution, has been reported in the setting of many different underlying functional and organic conditions. Only two cases of the syndrome following major head trauma have been reported. The authors present the first reported case of Capgras' syndrome following minor head trauma in an elderly woman.

Among the mentally ill, those with well-developed delusions are more likely to commit violent crimes against persons than those with chronic, undifferentiated psychoses. Reports of violence associated with delusional misidentification are reviewed and four patients described who were either perpetrators or victims of assaults as a consequence of the syndromes of Frégoli, Intermetamorphosis, Subjective Doubles and Capgras. The cases illustrate the multiplicity of factors which have to be taken into consideration in order to predict whether an individual will act in a violent manner on these delusions.

The study of a case of Capgras syndrome with striking clinical features illuminates the reality elements, affective conflicts, and cognitive processes that go into forming this specific delusion; and raises questions about the nosologic uniqueness of the entity. The meaning of the syndrome as a communication about an altered reality is highlighted.

A case is reported of Capgras syndrome arising as the major symptomatologic manifestation of a postpartum psychosis. Other diagnostic investigations have called into question the most recent etiopathogenetic interpretations which preclude the concomitant existence of an organic disorder, previously held to be a precondition for the development of Capgras syndrome.

A case of Capgras syndrome in a 67-year-old man who failed to improve on haloperidol, but responded to pimozide, is described. The patient's paranoid delusions abated with 8 mg per day of pimozide. We believe pimozide's established benefit in the treatment of delusional disorders warrants its consideration in alleviating other delusions, including "the delusion of doubles."