By Rangaprakash Deshpande, Tsz Man Lai, Wei Li, and Jamie Feusner, MD
Body dysmorphic disorder (BDD) is a psychiatric illness in which people misperceive defects in their appearance, disrupting their ability to function in their daily lives, with disturbing preoccupations, ritualistic behaviors, and emotional distress. Although the clinical symptoms of BDD are well-described, little is known about the causes or how the symptoms develop and progress over time.
Researchers in recent years have begun to build knowledge about how BDD sufferers’ brains function. We will summarize published research studies to date on the neurobiology of BDD, particularly findings related to neurocognitive functioning, neurochemistry, genetics, the visual system, and brain structure.
Individuals with BDD have shown deficiencies in memory in several studies1-4. In one study of verbal and nonverbal memory including visual organization strategies, subjects were asked to copy and recall a complicated figure drawing. The BDD group recalled more specific parts of the drawing instead of the overall structure, which may reflect poor organizational strategies marked by an imbalance in local (detail) and global information processing1. Another study using this test found impaired copying and recall, but not organization, in individuals with BDD2. There was also evidence of impaired visual working memory and of impaired auditory, verbal, and logical memory. Another study found no abnormalities in figure copying, but reduced verbal immediate memory and attention3. However, an additional study failed to demonstrate abnormal verbal immediate memory deficits in those with BDD2. Although there are some inconsistencies in findings, overall, these studies suggest that those with BDD may have multiple domains of memory deficiencies.
Decision-making, planning, inhibition, and organization:
BDD individuals also tend to do poorly in tasks related to decision-making, specifically those involving planning, inhibition, or organization4,5. One study found that compared to healthy controls, those with BDD made more errors on a search task, demonstrating deficits in working memory. They also were slower on a task measuring planning ability and exhibited higher risk-taking behavior in a decision-making experiment6.
Studies on emotional processing have revealed that individuals with BDD have deficiencies in recognizing facial emotions. One study found that individuals with BDD were more likely than healthy controls to misidentify neutral faces as angry7 or disgusted8. Another study found lower accuracy in identifying angry, sad, and neutral, faces; further, they were slower in identifying angry, happy, and neutral faces9. These studies implicate possible aberrant functioning of brain regions that process facial emotion, and perhaps faces in general given the latter studies’ findings with neutral faces.
Another study found that, compared with healthy participants, individuals with BDD perceive ambiguous situations as more threatening, whether the situations were related to the body, or were social or general situations10. In another study, researchers found that participants with BDD have more delayed responses to words that are considered salient to people with BDD, such as beauty or attractive, compared with neutral words11.
Given the previously uncovered abnormalities in facial emotional recognition, a brain imaging study was conducted to test functional brain connectivity in limbic (emotional processing) systems. At rest (not engaging in any task), individuals with BDD showed greater connectivity than controls between the left amygdala and the left middle and inferior temporal cortex, and the left superior frontal gyrus12. This suggests that emotional brain systems in those with BDD, compared with healthy controls, may more strongly influence visual systems. This could result in enhanced visual detail perception – noticing small imperfections – which those without BDD tend not to notice.
Neurochemical studies in BDD thus far have focused on the brain chemical serotonin and the hormone oxytocin.
Only one study has directly examined serotonergic functioning in individuals with BDD compared with healthy controls13. It found indirect evidence of abnormal serotonin function in those with BDD, as reflected by decreased serotonin binding densities.
Multiple treatment studies using medications called serotonin reuptake inhibitors showed that they significantly decrease BDD symptoms. These medications reduce the frequency and severity of worries about appearance and repetitive behaviors such as mirror checking. They also help relieve BDD-related emotional distress, reduce suicidal thinking, and improve patients’ insights into their illness14. Yet, although these observations suggest that serotonin might play a role in BDD, it does not prove that BDD patients have low serotonin levels or that abnormal serotonin levels cause BDD, since medications that affect the serotonergic system may simply lead to symptom reduction rather than “correcting” an underlying abnormal process.
Oxytocin is a hormone released by the brain that has multiple functions including affecting social interactions. One study found elevated serum oxytocin levels in those with BDD compared with healthy controls15. Further, oxytocin levels correlated with obsessive and compulsive BDD symptom severity, a finding that remained significant when controlling for medication use and depression and anxiety severity. This finding might be indirectly related to social problems in those with BDD, which can contribute to (as well as result from) their core symptoms of preoccupations, repetitive behaviors, and avoidance.
Thus, overall, there are early indications of possible neurochemical abnormalities in BDD. However, few studies have been conducted, and more research is needed to verify what, if any, neurochemical abnormalities are present in BDD and what the findings mean for people with BDD.
Genetics and Heritability
There have not been many genetic studies in BDD. However, there is evidence that BDD is heritable. Eight percent of individuals with BDD have a family member also diagnosed with BDD – a rate 3 to 5 times higher than in the general population16. A study of female twins found that genes accounted for about 44% of the propensity for dysmorphic worries17. Another twin study, in males and females, found BDD to be 42% heritable18. Yet another twin study, this time in male and female adolescents and young adults19, found heritability between 47% and 37%. Lower heritability was found in older age groups and in males in the younger age group. Finally, a small, preliminary study found an association between two different genes and BDD20. While genetic research is still in an early stage, these studies provide evidence of genetic contributions to BDD.
Several different types of studies have demonstrated that the brains of individuals with BDD perceive visual information differently than those without BDD.
Functional brain imaging studies of visual perception:
A brain imaging technique called functional magnetic resonance imaging (fMRI) allows researchers to compare brain activation patterns between people with BDD and healthy individuals, in order to pinpoint areas and systems in the brain that might function differently.
The first functional neuroimaging study in BDD examined visual processing of other people’s faces21. In this experiment, the photographs of faces were altered so that they included either only high or low levels of details. This produced images that contained only holistic and configural (overall, or “big picture”), or else mainly detailed visual information, respectively. The BDD group had greater brain activity than healthy controls in regions within a face-processing network on the left side of the brain for the low detail and the normal images; whereas healthy controls mainly used the right side of the brain during the task. The findings suggest that individuals with BDD engage in more detailed processing systems (generally left-sided) relative to those involved in holistic and configural processing (generally right-sided), even for images that contain little detail. This may explain increased attention to miniscule defects, and the subsequent inability to see them as inconsequential relative to the body as a whole22. One study also found the degree of detailed (as opposed to holistic) visual processing to be directly associated with how unattractive individuals with BDD perceive a face to be23.
The same research group performed a similar fMRI study using the participants’ own faces as stimuli. They found decreased activation in parts of the brain used for visual processing in the BDD group compared with controls when viewing low detail images, as well as increased activity in the frontal lobe and deeper parts of the brain when viewing normal images24. In addition, symptom severity (primarily relating to severity of obsessive thoughts and compulsive behaviors) was correlated with brain activity in secondary visual systems and frontostriatal systems in individuals with BDD. The abnormal frontostriatal activity in this imaging study is similar to what other studies have observed in obsessive-compulsive disorder (OCD), a related disorder. Another study found abnormalities in functional brain connectivity with a part of the frontal lobe called the orbito-frontal cortex in those with BDD, a region often associated with OCD pathology; the connectivity was also associated with obsessive-compulsive symptoms in BDD25. This may underlie BDD individuals’ obsessive thoughts and compulsive behaviors.
In a separate study, BDD patients were asked to do the same matching task while in an fMRI scanner but with images of houses instead of faces26. This study found that they had decreased activity in secondary visual processing regions compared with healthy controls in response to low detail images. This offers more evidence of abnormal holistic (“big picture”) processing. The fact that this occurred for non-appearance-related stimuli suggests that those with BDD may have general deficiencies in visual processing. A subsequent study of body processing again found lower activity in a part of the brain’s visual system that is used to capture the overall visual picture27. In addition, there was greater connectivity in the parietal lobe of the brain and visual regions of the brain – a pattern that partially overlapped with the pattern found in those with anorexia nervosa.
A study using electroencephalography (EEG), a technique that measures fluctuating electrical activity in the brain, examined responses to others’ faces and houses in individuals with BDD28. The magnitude of brain waves that happen approximately 170 ms after seeing the image were smaller in those with BDD than in healthy controls when viewing both faces and houses, and those with lower magnitudes of brain waves had worse insight. This suggests abnormal formation of visual memories of faces, which could contribute to perceptual distortions and poor insight in BDD. Another study used EEG to examine the electrophysiological correlates of global and local processing using upright and upside-down faces in individuals with BDD and healthy controls29. It found no differences between the two groups at several different time points after seeing the faces.
In sum, there is evidence in BDD of abnormal holistic and configural visual processing. The brains of people with BDD may not provide adequate visual “templates” for them to integrate and contextualize details such as minor flaws or imperfections, which could contribute to distortions in perceptions. Because people, in general, tend not to question what they see, this could lead those with BDD believing that what they perceive about their appearance is “real” and that others must also see them this way. This might result in poor insight about their illness, and a desire to pursue cosmetic solutions to try to fix (mis)perceived physical appearance problems.
Other studies of face processing:
Ability to detect flaws in facial features or asymmetry is another aspect of visual processing that researchers have studied in individuals with BDD. In one study, BDD participants perceived distortions in digital images of their own faces that were not actually present30. In another study, BDD participants were more accurate than healthy controls in detecting changes in aesthetic features of others’ faces31. Three studies32-34, but not a fourth35 found that those with BDD were faster and/or more accurate than healthy controls at identifying others’ faces that were upside-down, suggesting they have a superior ability to process details. Another study, in the context of an EEG experiment, did not find differences from controls in speed or accuracy at identifying upside-down faces29 (29). Discrepant findings on this task, importantly, could be due to different viewing durations. On balance, similar to the findings from brain imaging studies, these studies suggest that individuals with BDD have heightened sensitivity to detecting details, which may lead them to notice defects that are very minor or unnoticeable to others.
Studies of brain volumes and thickness:
Several BDD studies have examined brain volumes using neuroimaging. One small study found that females with BDD have more total white matter (brain tissue that transmits signals between different parts of the cortex – “highways” of communication in the brain) and abnormal symmetry in a deep (“subcortical”) brain region called the caudate nucleus, compared with healthy controls36. A study of white matter in males with BDD also found greater total white matter as well as smaller gray matter (where most of the brain cells are located) volumes in frontal brain regions called the anterior cingulate and the orbitofrontal cortex, on the left and the right37. A third study in males and females also found that the right orbitofrontal cortex and left anterior cingulate cortex were smaller in BDD participants than healthy controls38. Moreover, the longer they had BDD, the smaller their right orbitofrontal cortices were.
These studies provide evidence of abnormalities in frontostriatal systems in individuals with BDD. However, a fourth study did not find brain differences between BDD and control groups. It did, however, find a correlation between symptom severity and volumes in a region of the frontal cortex called the inferior frontal gyrus, and the right amygdala, which is involved in processing emotions39. Another study also found thinner gray matter in those with BDD in the middle temporal and inferior parietal regions40.
Another study in unmedicated individuals with BDD examined regions of the visual cortex in which previous brain imaging studies had found abnormal brain activation when viewing faces, bodies, and houses41. Those with BDD had significantly larger gray matter volume in visual regions. This could be an effect of abnormal brain development, or it could be a result of having BDD, and might relate to why those with BDD have differences in visual perception.
Some of these structural brain studies are not entirely consistent with each other. This may be due to the fact that each one studied relatively few individuals: one included just females36, one included just males30, and one included participants on medications, which may have affected brain volumes38. Thus, it is not clear to what degree there are abnormalities in brain structure in people with BDD, and how consistent this is person to person.
Studies of brain white matter:
Measurements of the white matter properties can be determined using a neuroimaging technique called diffusion tensor imaging (DTI). One such study found that individuals with BDD with worse insight had lower white matter fiber integrity in tracts connecting visual with emotion/memory processing systems42. Another brain study found lower fiber integrity in many major white matter tracts in the brains of individuals with BDD compared to healthy controls, suggesting widespread disorganized white matter structure in those with BDD43. These studies point to an association between impaired communication between brain regions and BDD symptoms.
Structural brain connectivity studies:
Brain network studies examine overall patterns of connections across the brain, rather than just connections between specific pairs of brain regions. A brain network analysis of white matter connectivity in individuals with BDD compared to healthy controls discovered that across the brain, individual regions were more highly connected with other local brain regions44. Also, those with more severe BDD symptoms had lower efficiency of brain connections. In addition, there were specific abnormal connections between regions involved in lower level and higher level visual and emotional processing. This may be associated with a disturbance, across the whole brain’s network, in how visual information is processed emotionally in those with BDD.
Summary of studies of brain structure:
There is some evidence (although it is not entirely consistent) of abnormal gray matter volumes and reduced white matter integrity. In addition, there is evidence of abnormal white matter brain connectivity (“the wiring”) in people with BDD. Inefficient connections between these brain regions may underlie impairments in visual, emotional, and possibly other types of information processing.
BDD is a complex psychiatric disorder that includes symptoms that span many domains, and thus the neurobiology is likely equally as complex and may vary person to person. In other words, there may be subgroups of individuals with BDD who have certain neurobiological factors that are not necessarily shared across all groups. However, the following are several general patterns that are emerging from evidence from research studies:
- Impairments in neurocognitive functioning, especially in planning, organization, decision making, attention, and memory
- Visual processing abnormalities characterized by an imbalance in how those with BDD process holistic and detailed visual information, with excessive visual processing of detail and difficulty seeing “the big picture”
- Emotional processing deficiencies, including deficits in processing and interpreting facial emotions
- Impairments in brain connections between the frontal lobe and deeper brain structures (frontostriatal circuits), which mediate higher-level regulation and behavioral control
- Abnormal white matter connectivity and brain network patterns in the brains of those with BDD
- Potential abnormalities in neurochemicals such as oxytocin and/or serotonin
Interactions between these aberrantly functioning brain systems, as well as possible abnormalities in neurotransmitter/neurochemical systems may contribute to many of the symptoms in BDD. These neurobiological abnormalities may affect the “core” symptoms of misperception of appearance (visual processing abnormalities) and propensities for engaging in repetitive behaviors (frontostriatal circuits). Other neurobiological abnormalities may be linked to other commonly occurring symptoms and experiences of those with BDD such as subtle neurocognitive impairment as well as social-emotional difficulties.
Promising new research has started to identify abnormal areas and connections in the brain in hopes of developing biomarkers or brain correlates that can help identify those at risk for developing BDD. Because of the complexity of the disorder, much future research is necessary to understand what causes BDD and contributes to the development of BDD symptoms (including neurobiological as well as interpersonal, social, cognitive, and behavioral factors) and how those findings can lead to better treatment approaches.
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