Monothematic delusion
Encyclopedia
A monothematic delusion is a delusion
al state that only concerns one particular topic. This is contrasted by what is sometimes called multi-thematic or polythematic delusions where the person has a range of delusions (typically the case of schizophrenia
). These disorders can occur within the context of schizophrenia or dementia
or they can occur without any other signs of mental illness. When these disorders are found outside the context of mental illness, they are often caused by organic disfunction as a result of traumatic brain injury
, stroke
, or neurological illness.
People who suffer from these delusions as a result of organic dysfunction
often do not suffer from any obvious intellectual deficiency nor do they have any other symptoms. Additionally, a few of these people even have some awareness that their beliefs are bizarre, yet they cannot be persuaded that their beliefs are false.
Note that some of these delusions are sometimes grouped under the umbrella term of delusional misidentification syndrome
.
research points toward a two-factor approach to the cause of monothematic delusions. The first factor being the anomalous experience—often a neurological defect—which leads to the delusion and the second factor being an impairment of the belief formation cognitive process.
For example of one of these first factors, several studies point toward Capgras delusion being the result of a disorder of the affect
component of face perception
. As a result, while the person can recognize their spouse (or other close relation) they do not feel the typical emotional reaction and thus the spouse does not seem like the person they once knew.
As studies have shown, these neurological defects are not enough on their own to cause delusional thinking. An additional second factor, a bias or impairment of the belief formation cognitive process is required to solidify and maintain the delusion. Since we do not currently have a solid cognitive model of the belief formation process, this second factor is still somewhat of an unknown.
Some research has shown that delusional people are more prone to jumping to conclusions and thus they would be more likely to take their anomalous experience as veridical and make snap judgments based on these experiences. Additionally, studies have shown that they are more prone to making errors due to matching bias—indicative of a tendency to try and confirm the rule. These two judgment biases help explain how delusion prone people could grasp onto extreme delusions and be very resistant to change.
Researchers claim this is enough to explain the delusional thinking. However other researchers still argue that these biases are not enough to explain why they remain completely impervious to evidence over time. They believe that there must be some additional unknown neurological defect in the patient's belief system (probably in the right hemisphere).
Delusion
A delusion is a false belief held with absolute conviction despite superior evidence. Unlike hallucinations, delusions are always pathological...
al state that only concerns one particular topic. This is contrasted by what is sometimes called multi-thematic or polythematic delusions where the person has a range of delusions (typically the case of schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
). These disorders can occur within the context of schizophrenia or dementia
Dementia
Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...
or they can occur without any other signs of mental illness. When these disorders are found outside the context of mental illness, they are often caused by organic disfunction as a result of traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
, stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, or neurological illness.
People who suffer from these delusions as a result of organic dysfunction
Organic disease
An organic disease is one which involves or affects physiology or bodily organs. A disease in which there is a physiological change to some tissue or organ of the body....
often do not suffer from any obvious intellectual deficiency nor do they have any other symptoms. Additionally, a few of these people even have some awareness that their beliefs are bizarre, yet they cannot be persuaded that their beliefs are false.
Types
The delusions that fall under this category are:- Capgras delusionCapgras delusionThe Capgras delusion theory 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 belief that (usually) a close relative or spouse has been replaced by an identical-looking impostor. - Fregoli delusionFregoli delusionThe Fregoli delusion or the delusion of doubles is a rare disorder in which a person holds a delusional belief that different people are in fact a single person who changes appearance or is in disguise...
: the belief that various people who the believer meets are actually the same person in disguise. - IntermetamorphosisIntermetamorphosisIntermetamorphosis is a delusional misidentification syndrome, related to agnosia. The main symptoms consist patients believing that they can see others change into some one else both external appearance and internal personality...
: the belief that people in one's environment swap identities with each other whilst maintaining the same appearance. - Subjective doublesSyndrome of subjective doublesThe syndrome of subjective doubles is a rare delusional misidentification syndrome in which a person experiences the delusion that he or she has a double or Doppelgänger with the same appearance, but usually with different character traits and leading a life of its own. Sometimes the patient has...
: a person believes there is a doppelgängerDoppelgängerIn fiction and folklore, a doppelgänger is a paranormal double of a living person, typically representing evil or misfortune...
or double of him or herself carrying out independent actions. - Cotard delusionCotard delusionThe Cotard delusion or Cotard's syndrome or Walking Corpse Syndrome is a rare neuropsychiatric disorder in which people hold a delusional belief that they are dead , do not exist, are putrefying, or have lost their blood or internal organs...
: the belief that oneself is dead or does not exist; sometimes coupled with the belief that one is putrifying or missing internal organs. - Mirrored self-misidentificationMirrored self-misidentificationMirrored-self misidentification is the delusional belief that one's reflection in a mirror is some other person . Often people who suffer from this delusion are not delusional about anything else. It is considered a monothematic delusion; it is sometimes labeled a delusional misidentification...
: the belief that one's reflection in a mirror is some other person. - Reduplicative paramnesiaReduplicative paramnesiaReduplicative paramnesia is the delusional belief that a place or location has been duplicated, existing in two or more places simultaneously, or that it has been 'relocated' to another site...
: 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 in an identical-looking hospital in a different part of the country. - SomatoparaphreniaSomatoparaphreniaSomatoparaphrenia is a type of monothematic delusion where one denies ownership of a limb or an entire side of one's body. As an example, a patient would believe that her or his own arm would belong to the doctor, or that another patient left it behind....
: the delusion where one denies ownership of a limb or an entire side of one's body (often connected with stroke).
Note that some of these delusions are sometimes grouped under the umbrella term of delusional misidentification syndrome
Delusional misidentification syndrome
Delusional misidentification syndrome is an umbrella term, introduced by Christodoulou 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...
.
Causes
Current cognitive neuropsychologyCognitive neuropsychology
Cognitive neuropsychology is a branch of cognitive psychology that aims to understand how the structure and function of the brain relates to specific psychological processes. It places a particular emphasis on studying the cognitive effects of brain injury or neurological illness with a view to...
research points toward a two-factor approach to the cause of monothematic delusions. The first factor being the anomalous experience—often a neurological defect—which leads to the delusion and the second factor being an impairment of the belief formation cognitive process.
For example of one of these first factors, several studies point toward Capgras delusion being the result of a disorder of the affect
Affect (psychology)
Affect refers to the experience of feeling or emotion. Affect is a key part of the process of an organism's interaction with stimuli. The word also refers sometimes to affect display, which is "a facial, vocal, or gestural behavior that serves as an indicator of affect" .The affective domain...
component of face perception
Face perception
Face perception is the process by which the brain and mind understand and interpret the face, particularly the human face.The human face's proportions and expressions are important to identify origin, emotional tendencies, health qualities, and some social information. From birth, faces are...
. As a result, while the person can recognize their spouse (or other close relation) they do not feel the typical emotional reaction and thus the spouse does not seem like the person they once knew.
As studies have shown, these neurological defects are not enough on their own to cause delusional thinking. An additional second factor, a bias or impairment of the belief formation cognitive process is required to solidify and maintain the delusion. Since we do not currently have a solid cognitive model of the belief formation process, this second factor is still somewhat of an unknown.
Some research has shown that delusional people are more prone to jumping to conclusions and thus they would be more likely to take their anomalous experience as veridical and make snap judgments based on these experiences. Additionally, studies have shown that they are more prone to making errors due to matching bias—indicative of a tendency to try and confirm the rule. These two judgment biases help explain how delusion prone people could grasp onto extreme delusions and be very resistant to change.
Researchers claim this is enough to explain the delusional thinking. However other researchers still argue that these biases are not enough to explain why they remain completely impervious to evidence over time. They believe that there must be some additional unknown neurological defect in the patient's belief system (probably in the right hemisphere).
See also
- Cognitive neuropsychiatryCognitive neuropsychiatryCognitive neuropsychiatry is a sub-discipline of psychology and psychiatry that aims to understand mental illness and psychopathology in terms of models of normal psychological function. It is also a way of uncovering normal psychological processes by studying the effects of their change or...
- Cognitive neuropsychologyCognitive neuropsychologyCognitive neuropsychology is a branch of cognitive psychology that aims to understand how the structure and function of the brain relates to specific psychological processes. It places a particular emphasis on studying the cognitive effects of brain injury or neurological illness with a view to...
- NeuropsychologyNeuropsychologyNeuropsychology studies the structure and function of the brain related to specific psychological processes and behaviors. The term neuropsychology has been applied to lesion studies in humans and animals. It has also been applied to efforts to record electrical activity from individual cells in...
- Philosophy of mindPhilosophy of mindPhilosophy of mind is a branch of philosophy that studies the nature of the mind, mental events, mental functions, mental properties, consciousness and their relationship to the physical body, particularly the brain. The mind-body problem, i.e...
- NeurocognitiveNeurocognitiveNeurocognitive is a term used to describe cognitive functions closely linked to the function of particular areas, neural pathways, or cortical networks in the brain substrate layers of neurological matrix at the cellular molecular level...
- Cognitive neuroscienceCognitive neuroscienceCognitive neuroscience is an academic field concerned with the scientific study of biological substrates underlying cognition, with a specific focus on the neural substrates of mental processes. It addresses the questions of how psychological/cognitive functions are produced by the brain...
- DelusionDelusionA delusion is a false belief held with absolute conviction despite superior evidence. Unlike hallucinations, delusions are always pathological...
- Face perceptionFace perceptionFace perception is the process by which the brain and mind understand and interpret the face, particularly the human face.The human face's proportions and expressions are important to identify origin, emotional tendencies, health qualities, and some social information. From birth, faces are...
- BeliefBeliefBelief is the psychological state in which an individual holds a proposition or premise to be true.-Belief, knowledge and epistemology:The terms belief and knowledge are used differently in philosophy....
External links
- The Belief Formation Project a project of the Macquarie Centre for Cognitive Science, which uses research on delusions with the aim of developing a cognitive model of beliefs