Amy MacKinnon is a graduate student at Western University studying philosophy of psychiatry, mind-brain sciences, and disability. Muhammad Ali Khalidi is Presidential Professor of Philosophy at CUNY Graduate Center. His book, Cognitive Ontology: Taxonomic Practices in the Mind-Brain Sciences, will be published by Cambridge University Press in 2022.
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| Amy MacKinnon |
Understanding the nature of psychiatric disorders is something that philosophers of psychiatry, as well as practicing psychiatrists and psychotherapists, are concerned about. Every so many years, after a long revision process, a new Diagnostic and Statistical Manual of Mental Disorders (DSM) is produced by the American Psychiatric Association. In the most recent edition (DSM-5), as in all previous editions, some disorders were removed, some re-named, and some new ones added. With each revision, the hope is that we are gaining validity and reliability.
As philosophers, we’re interested in the underlying basis of these classifications, so we decided to examine one particular psychiatric disorder, Body Dysmorphic Disorder (BDD), to better understand the grounds for psychiatric classification. In the DSM-5, BDD is classified under the category of Obsessive-Compulsive Related Disorders (OCRDs). The main feature of BDD is that it involves persistent and intrusive thoughts about a perceived bodily flaw that is not observable or appears slight to others.
At some point during the course of the disorder, an individual with BDD will have performed repetitive behaviors (e.g. mirror checking, excessive grooming, skin picking, reassurance seeking) or mental acts (e.g. comparing his or her appearance with that of others) in response to concerns about their own appearance. The preoccupation causes clinically significant distress or impairment in social, occupational or other areas of functioning. Moreover, the preoccupation with appearance is not better explained by concerns with body fat or weight, and symptoms do not otherwise meet diagnostic criteria for an eating disorder.
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| Muhammad Ali Khalidi |
On the surface, it might seem as though BDD is aptly classified as an OCRD in so far as it shares some similar features with the four other disorders in the OCRD category (namely, obsessive-compulsive disorder, hoarding disorder, trichotillomania, and excoriation). But we think that even though BDD does have obsessive and compulsive components, the similarities are superficial. Though BDD and OCD patients both engage in repetitive behaviors that they have difficulty controlling, the underlying causes seem quite different.
Various philosophers of science, from John Stuart Mill to Ruth Millikan, have proposed that the basis of scientific classification ought to be causal and that valid categories in science should track causal relationships. Building on this basic insight, we argue that by focusing on the etiology of the disorder, it becomes apparent that the differences between BDD and OCD are such that they should not both be subsumed under the category of OCRD. We propose a tentative causal model of BDD that sets it apart as a psychiatric disorder and corroborates the claim that it has been misclassified in the DSM-5. Reclassification of BDD on the basis of its causal profile should have implications for the diagnosis and treatment of patients.
We think that there are three causal factors implicated in BDD that do not appear to be present in the disorders that it has been classified with. BDD involves a perceptual deficit that is not apparent in OCD. People with BDD tend to focus on details at the expense of the whole picture or “configural” features. Neuropsychological studies suggest that those with BDD tend to over-focus on minor details when drawing complex figures from memory, compared to those without BDD. This is congruent with other research suggesting that people with BDD are more likely to examine details in visual tasks and less likely to take in the holistic picture. This phenomenon seems to be supported by studies in which people with BDD and controls perform matching tasks (e.g. matching images of inverted faces).
In addition to a perceptual deficit, people with BDD also have distinctive cognitive deficits. Compared to people with OCD, people with BDD show a theory of mind deficit and they engage in referential thinking especially when it comes to social situations. People with BDD tend to have difficulty in understanding others’ intentions and attitudes in social settings. When asked to observe video sequences of a dinner party and report on those people’s attitudes and intentions, people with BDD tend to perform poorly relative to controls. When it comes to referential thinking, people with BDD tend to perceive neutral or even positive stimuli as being negative. A smile from a stranger on the sidewalk is more likely to be perceived as a mocking gesture rather than a friendly greeting.
People with BDD also seem to differ from those with OCD when it comes to level of insight into their own condition. Whereas people with OCD usually have a fair level of insight, those with BDD tend to show poor insight. People with OCD will often report knowing that their behaviour – such as checking the stove 20 times to make sure it is off -- is senseless. They might know that checking once is enough, but they still carry out the ritual of checking repeatedly. By contrast, people with BDD really believe that their body is mis-shaped, and they think that they are justified in mirror-checking as often as they do. In other words, they have different attitudes towards their own behaviours. Moreover, BDD patients also report feeling worse after engaging in repetitive behaviors and experience no reduction in anxiety, as compared with OCD patients, whose rituals seem to relieve their anxiety, albeit temporarily.
Additionally, people with BDD are resistant to others’ attempts at reassurance and reject evidence that contradicts their beliefs. No matter how often someone says, “your nose looks fine,” or provides evidence that their facial features are not asymmetrical, people with BDD do not accept this information. This suggests that they might have a strong version of a confirmation bias, which has also been found in other psychiatric patients with entrenched delusions, such as those with schizophrenia. Meanwhile, OCD patients do not seem to have such entrenched delusions. This cognitive bias may be a third causal factor that is distinctive of BDD and contributes to the occurrence of the disorder.
These contrasts with OCD have led us to posit a causal model of the emergence and persistence of BDD in certain people. We conjecture that their perceptual abnormality may lead them to focus excessively on specific body parts, which may result in dissatisfaction with their appearance. Moreover, their theory of mind deficit may lead them to think that others disapprove of their appearance, further confirming their own dissatisfaction. These negative attitudes may be reinforced by an exaggerated form of confirmation bias, which helps give rise to a full-blown delusion about their appearance that is difficult to dislodge and bring about a lack of insight into their own condition. We conjecture that these three causal factors, when found together in a single individual, result in this distinctive psychiatric condition and set it apart from the disorders that it has been lumped with in the DSM-5.
Various philosophers of science, from John Stuart Mill to Ruth Millikan, have proposed that the basis of scientific classification ought to be causal and that valid categories in science should track causal relationships. Building on this basic insight, we argue that by focusing on the etiology of the disorder, it becomes apparent that the differences between BDD and OCD are such that they should not both be subsumed under the category of OCRD. We propose a tentative causal model of BDD that sets it apart as a psychiatric disorder and corroborates the claim that it has been misclassified in the DSM-5. Reclassification of BDD on the basis of its causal profile should have implications for the diagnosis and treatment of patients.
We think that there are three causal factors implicated in BDD that do not appear to be present in the disorders that it has been classified with. BDD involves a perceptual deficit that is not apparent in OCD. People with BDD tend to focus on details at the expense of the whole picture or “configural” features. Neuropsychological studies suggest that those with BDD tend to over-focus on minor details when drawing complex figures from memory, compared to those without BDD. This is congruent with other research suggesting that people with BDD are more likely to examine details in visual tasks and less likely to take in the holistic picture. This phenomenon seems to be supported by studies in which people with BDD and controls perform matching tasks (e.g. matching images of inverted faces).
In addition to a perceptual deficit, people with BDD also have distinctive cognitive deficits. Compared to people with OCD, people with BDD show a theory of mind deficit and they engage in referential thinking especially when it comes to social situations. People with BDD tend to have difficulty in understanding others’ intentions and attitudes in social settings. When asked to observe video sequences of a dinner party and report on those people’s attitudes and intentions, people with BDD tend to perform poorly relative to controls. When it comes to referential thinking, people with BDD tend to perceive neutral or even positive stimuli as being negative. A smile from a stranger on the sidewalk is more likely to be perceived as a mocking gesture rather than a friendly greeting.
People with BDD also seem to differ from those with OCD when it comes to level of insight into their own condition. Whereas people with OCD usually have a fair level of insight, those with BDD tend to show poor insight. People with OCD will often report knowing that their behaviour – such as checking the stove 20 times to make sure it is off -- is senseless. They might know that checking once is enough, but they still carry out the ritual of checking repeatedly. By contrast, people with BDD really believe that their body is mis-shaped, and they think that they are justified in mirror-checking as often as they do. In other words, they have different attitudes towards their own behaviours. Moreover, BDD patients also report feeling worse after engaging in repetitive behaviors and experience no reduction in anxiety, as compared with OCD patients, whose rituals seem to relieve their anxiety, albeit temporarily.
Additionally, people with BDD are resistant to others’ attempts at reassurance and reject evidence that contradicts their beliefs. No matter how often someone says, “your nose looks fine,” or provides evidence that their facial features are not asymmetrical, people with BDD do not accept this information. This suggests that they might have a strong version of a confirmation bias, which has also been found in other psychiatric patients with entrenched delusions, such as those with schizophrenia. Meanwhile, OCD patients do not seem to have such entrenched delusions. This cognitive bias may be a third causal factor that is distinctive of BDD and contributes to the occurrence of the disorder.
These contrasts with OCD have led us to posit a causal model of the emergence and persistence of BDD in certain people. We conjecture that their perceptual abnormality may lead them to focus excessively on specific body parts, which may result in dissatisfaction with their appearance. Moreover, their theory of mind deficit may lead them to think that others disapprove of their appearance, further confirming their own dissatisfaction. These negative attitudes may be reinforced by an exaggerated form of confirmation bias, which helps give rise to a full-blown delusion about their appearance that is difficult to dislodge and bring about a lack of insight into their own condition. We conjecture that these three causal factors, when found together in a single individual, result in this distinctive psychiatric condition and set it apart from the disorders that it has been lumped with in the DSM-5.
This perceptual-cognitive causal account of BDD may serve as a model for other psychiatric disorders, some of which may also emerge as a result of atypical perceptual and cognitive traits. By examining the underlying causes, as well as focusing on the patients’ own perspectives and attitudes, rather than just looking at outward symptoms, it becomes apparent that BDD is sufficiently different from OCD that they should not be classified in the same category. We believe that this is important when it comes to understanding the validity of the classification, and we think this could have important implications for understanding effective treatments in the form of causal interventions.