Misidentification delusions

Chapter 13
Misidentification delusions


Michael H. Connors1,2, Robyn Langdon1, and Max Coltheart1


1  ARC Centre of Excellence in Cognition and Its Disorders, and Department of Cognitive Science, Macquarie University, Sydney, Australia


2 Dementia Collaborative Research Centre, School of Psychiatry, University of New South Wales, Sydney, Australia


Introduction


Misidentification delusions involve an incorrect belief about the identity of other people, oneself, animals, objects, or places. To meet the definitional criteria of a delusion, this belief needs to be fixed and resistant to counterevidence. In some patients, however, the delusional belief may appear at different times or fluctuate in intensity. Although encompassing many different types of beliefs, misidentification delusions share two common elements: (1) a misidentified entity, and (2) an incorrect belief about the identity of that entity. In the case of Capgras delusion, for example, patients believe that a known person (the misidentified entity) has been replaced by a visually similar impostor (the incorrect belief). In the case of reduplicative paramnesia for place, patients believe that a location (the misidentified entity) has been duplicated (the incorrect belief).


These two elements—a misidentified entity and an incorrect belief about the identity of the entity—distinguish misidentification delusions from other types of delusions. Unfortunately, though, the term misidentification delusion has sometimes been used rather loosely in the psychiatric literature. Some authors [1, 2], for example, have referred to Cotard delusion—the belief that one is dead—as a misidentification delusion. In this case, however, there is no misidentified entity, only the ascription of an incorrect property to the correctly identified entity. The belief thus does not constitute a misidentification delusion. In a similar way, the phantom boarder delusion—the belief that there are uninvited strangers living in one’s house—and sex change delusion—the belief that one has changed sex—are not strictly misidentification delusions, even though they have been referred to as such, because there is no misidentified entity.


Other authors have used the term misidentification delusion to refer exclusively to delusions that involve misidentification of other people [3, 4]. These authors have tended to focus on four main delusions—namely, Capgras, Frégoli (the belief that strangers are known people in disguise), intermetamorphosis (the belief that some person has changed into another person), and subjective doubles (the belief in a physical or psychological double). Although misidentification delusions certainly include these four well-known person misidentification delusions, the term itself is broader and need not exclude other forms of misidentification. Misidentification delusions can also apply to oneself, pets, inanimate objects, and places. Indeed, other authors [5] have even applied the term to delusions involving misattribution of body parts, such as somatoparaphrenia (the belief that one’s limb is owned by someone else). For the purposes of simplicity, however, the current chapter restricts attention to delusions focused on the identity of an entity in its entirety, rather than just a part of it. Delusions such as somatoparaphrenia, nevertheless, occupy an intermediate area for the purposes of classification and highlight some of the challenges for a complete taxonomy.


Variety of misidentification delusions


Misidentification delusions can be classified according to the type of misidentified entity. There are four broad subtypes: other people and other sentient beings; oneself; inanimate objects; and places. Within each subtype, delusions differ in their belief about the misidentified entity (see Table 13.1). Common beliefs include that the entity has been duplicated, replaced, or transformed into another entity.


Table 13.1 Common misidentification delusions.

























































Misidentified entity Belief about misidentified entity Delusion
Other person Replaced by impostor Capgras

Duplicated without replacement Reduplicative paramnesia

Transformed into another person Intermetamorphosis

Another person in disguise Frégoli

The misidentified person is simply another person, physically and psychologically Generic misidentification of other people
Self Duplicated Subjective doubles

Changed into another person Reverse intermetamorphosis

Changed into an animal Lycanthropy
(Mirror reflection) Mirror reflection is not oneself Mirrored-self misidentification
Inanimate object Replaced by impostor Inanimate doubles

Objects are animate companions Delusional companions
(Television image) Television image is physical reality Misidentification of television
(Photograph) Photograph is three-dimensional reality Misidentification of photograph
Place Duplicated Reduplicative paramnesia

Other people and other sentient beings


Capgras delusion


Capgras delusion is the belief that a known other person has been replaced by an impostor of similar appearance [6]. The delusion usually centres on people familiar to the patients whom the patients believe have been replaced by unfamiliar yet similar-looking impostors. Patients often point out what they take to be subtle differences in physical appearance and behaviour between the person and the supposed impostor as confirming their belief. In an early case [7], for example, a 53-year-old woman with schizophrenia believed that her husband, children, police chief, and neighbours had been replaced by visually similar impostors. This patient reported that she could distinguish these impostors by such features as “a little mark on the ear … a thinner face … the way of speaking … the way of walking” [8] (p. 129). In some patients, the delusion is limited to a single impostor of a known person. In most patients, though, the delusion involves multiple impostors of known people. This may include objects and animals that patients believe have similarly been replaced by visual look-alikes [9–12]. The number of impostors may also increase over time. In some cases, the belief can result in violence. In a typical case involving violence [13], for example, a 19-year-old male patient stabbed his mother under the belief that she had been replaced by an evil robot of identical appearance.


Reduplicative paramnesia


Reduplicative paramnesia for people is the belief that a person has been duplicated (reduplicative paramnesia can also apply to places and objects). Unlike Capgras, there is no sense of the original person being replaced or of the duplicate being an impostor look-alike. In one case [14], a 76-year-old female patient, who had recently suffered a right parietal stroke, believed that there were two versions of her husband. The patient correctly reported that her husband was dead but also maintained that her husband was currently a patient in the same hospital as her. The “patient husband” was a duplicate of the “dead husband,” albeit alive. The patient did not offer an explanation of how this was possible, but insisted that she was certain in her convictions. The patient also reported that other members of her family—including her two daughters, a grandson, and the father-in-law of one of her daughters—worked at the hospital or were patients there. In many patients, the delusion may co-occur with belief in the duplication of places and objects as well as people.


Intermetamorphosis


Intermetamorphosis is the belief that a person has changed into another person. Patients typically believe the new identity differs both physically and psychologically from the original person. In an early case [15], for example, a 49-year-old woman believed that her husband and her son had both transformed into other people, including neighbours and cousins. The patient described the change: “In a second my husband is taller, smaller or younger” [8, p. 140]. The patient pointed to physical characteristics and behaviour that she believed had changed with the transformation, and other characteristics that she believed had not changed and that indicated her husband’s true identity. Unlike her husband, whom she believed transformed radically in appearance, the patient believed that her son transformed into people of similar appearance to himself and that she could only identify him by his large and dirty shoes. The patient came to believe that all inhabitants in the area—with the exception of herself—could change themselves into one another.


Frégoli delusion


Frégoli delusion is the belief that a stranger is a known person in disguise. Patients are thus aware of physical differences between the known person’s usual appearance and what they take to be their disguise (i.e., the stranger’s appearance), yet maintain that the two people are the same person. In an early case [16], a 27-year-old woman in Paris believed that two actresses of the time (Sarah Bernhardt and Robine) were following her in different disguises “taking the form of people she knows or meets” [8, p. 134]. In particular, the patient believed the actresses disguised themselves as strangers in the street, doctors, friends, and previous employers. The patient believed that she was being persecuted by the actresses and even attacked a woman on the street whom she believed was Robine. The delusion was named after the Italian actor and mimic Leopoldo Frégoli because of his ability to impersonate other people. The delusion is often seen in the context of paranoia and the belief that one is being persecuted [17–19]. Cases not involving paranoia or persecution have been reported, though, such as a patient who believed that friends of her family were disguising themselves as strangers in order to protect her [20] and another patient who believed that family members were disguising themselves for their own personal non-threatening reasons [21].


Generic misidentification of other people


Generic misidentification of other people involves the belief that one person is simply another person, without any notion of transformation or disguise. In one case, a 74-year-old female patient with Alzheimer’s disease believed that her daughter was her sister and resisted attempts by both her daughter and her doctors to convince her otherwise [22]. When shown photographs of her family, this patient would also misidentify her other daughter as her sister and misidentify her husband as her father.


Oneself


Subjective doubles


The delusion of subjective doubles is the belief that one has a double, or doppelganger. In a well-known case [23], an 18-year-old female patient, following a febrile episode, believed that a neighbour and at least two other female patients were capable of transforming themselves into her doubles. The patient believed the doubles had the “same face, same build, same clothes, same everything” (p. 250) as herself and that the perpetrators used special makeup, a wig, and a mask to effect the transformation. She later attacked one of the patients whom she believed was impersonating her; as she was pulled away, she begged her doctor to “pull the mask” (p. 250) from the patient’s face. Although this particular patient reported that specific people were her double, other patients with this delusion may not specify this and simply indicate that their double exists and is elsewhere [24]. The delusion can involve both physical and psychological doubles. Most cases involve physical doubles in which the patient believes that another person is almost indistinguishable from themselves in appearance, as in the example of the 18-year-old female patient described above. Some cases, however, involve psychological doubles in which the patient believes that people with dissimilar physical bodies hold minds identical to that of the patient [25]. Cases of both physical and psychological duplicates also exist [26]. In some complicated cases, the patient may even believe that they themselves are the impostor [24]. The delusion of subjective doubles often co-occurs with Capgras delusion and persecutory beliefs [24].


Reverse intermetamorphosis


Reverse intermetamorphosis is the belief that one has changed into another person. In one case [14], for example, a 40-year-old female patient with schizophrenia believed that she was her father or, occasionally, her grandfather. The patient would only respond to her father’s name and signed her father’s name. The patient gave her father’s history when questioned about her personal history and described herself as she would her father. Other patients may believe that they have become a person of high status or of particular importance [27]. A complicated variant of reverse intermetamorphosis is the belief that one’s mind resides in another person’s body [24]. The patient believes that their mind has replaced the mind of the person whose body they are using. The patient thus does not recognise their physical body as their own [28, 29].


Lycanthropy


Another variant of reverse intermetamorphosis is lycanthropy, the belief that one has transformed into an animal [30]. The delusion has been reported for over 2000 years and is referred to in some of the earliest medical writings [31]. Although the delusion may be more common in rural areas and pre-industrialised countries, it is still found in modern Western cities. One study [32], for example, reported 12 cases in a major Boston psychiatric hospital over a 12-year period. The delusion is often associated with wolves or werewolves, but patients may believe they are other animals such as dogs, pigs, birds, rabbits, cats, gerbils, frogs, bees, lions, tigers, hyenas, sharks, and crocodiles. Although some patients may verbally insist that they are a particular animal, others may not speak (since they are animals) and simply behave as though they were an animal by howling, growling, or crawling on all fours. In one such case [33], a 66-year-old woman with psychotic depression, believing that she was a dog, would get down on her hands and knees and bark.


Mirrored-Self misidentification


Mirrored-self misidentification is the belief that one’s reflection is not oneself [34]. Some patients identify their mirrored-reflection as a stranger. In one case [35], for example, a 77-year-old male patient believed that his reflection was a “dead ringer” for himself but that he did not know who this person was. Other patients report that their mirrored reflection is a known person, such as a family member. In one case [36], for example, a 62-year-old female patient believed that her reflection was her sister, who had died 2 years earlier. The delusion can occur despite an intact semantic understanding of mirrors (e.g., being able to define mirrors and reflections) and despite being able to identify other people in the mirror [35]. Some patients can also recognise themselves in photographs [35]. Patients may talk to the “stranger” in the mirror. Whereas some patients are indifferent [35] or treat the “stranger” as a friend [37], others are deeply suspicious and upset by the “stranger” [38]. Patients have been known to throw objects at mirrors or cover up all reflective surfaces to avoid seeing the stranger [38].


Inanimate objects


Delusion of inanimate doubles


The delusion of inanimate doubles involves the belief that an inanimate object has been replaced by an almost identical duplicate. The duplicate is usually, though not always, of inferior quality to the original. The objects are usually personal possessions and can include, for example, furniture, household appliances, clothing, spectacles, jewellery, and even handwritten letters and personal identification cards. In one case [39], for example, a 38-year-old male patient believed that his car, various personal belongings, and some of his clothing had been replaced by duplicate objects. The patient pointed to specific differences between the original object and what he considered to be its duplicate (e.g., a lower dashboard in the car and fewer gears on the gearstick). The delusion of inanimate doubles often occurs in the context of paranoia. The delusion can occur by itself, though it can also occur with other delusions, most frequently Capgras. Between 5 and 14 percent of patients with Capgras delusion also report the delusion of inanimate doubles [10–12].


Delusional companions


Delusional companions is the belief that inanimate objects are sentient companions. Although more common in the later stages of dementia, patients in the early stages of dementia with no other symptoms can also report the delusion [40]. In one case [40], for example, an 81-year-old female patient with relatively preserved cognition (mini-mental state examination score of 28/30) and no other unusual beliefs or symptoms would converse with a teddy bear. The patient would have long conversations with the teddy bear, coax it to read newspapers, and take it on drives with her. The patient also tried to encourage her teddy-bear to eat and drink, and became anxious when it did not respond. When visited by her doctor, the patient removed the teddy from the room in order, she explained, to preserve confidentiality.

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May 29, 2017 | Posted by in PSYCHIATRY | Comments Off on Misidentification delusions
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