A neuropsychological investigation of the link between anorexia nervosa and autism
Anorexia nervosa (AN) is an enigmatic deadly disorder that predominantly affects adolescent girls. Although AN is primarily characterized by restricted eating, recent research emphasize consistently elevated rates of social cognitive impairments typical of high-functioning autism spectrum disorder (ASD). The goal of this work is to contribute to the controversial yet long-standing theory that AN may be a manifestation of ASD in women by (i) identifying social cognitive behavioral and brain impairments in women with AN, (ii) determining the degree to which the identified impairments are shared with women with ASD, and (iii) establishing whether the identified impairments persist after recovery from AN. To do so, we will conduct a series of behavioral and functional magnetic resonance imaging (MRI) studies of social cognition in women with AN, women with ASD, and healthy controls. The results will provide the first evidence for or against shared social brain impairments in AN and ASD, critically contributing to the decades-old debate about the relationship between the two disorders. Our work will also improve the neuropsychological understanding of eating disorders, and, in the longer term, lead to improved treatment options for women with anorexia nervosa.
Final report
Purpose, development and implementation
The purpose of this project was to characterize the neuropsychological link between anorexia nervosa and autism, with a specific focus on social processes. The project developed largely according to the plan, with some additions due to the covid-19 pandemic. We used magnetic resonance imaging to assess brain anatomy and function, and psychometric questionnaires and tests to examine behavior. We have investigated similarities and differences between patients diagnosed with anorexia and autism, and due to covid-19 limiting patient recruitment in clinics, we also included a large non-clinical community sample. In this community sample, we benefited from the fact that both eating disorders and autism are spectrum conditions and we could characterize the association between measurable symptoms of anorexia and symptoms of autism. In total, the project has analyzed data in over 350 participants. In addition, we supplemented the study with data in people with diagnosed anorexia and autism from large international collaborative projects.
The three most important results and conclusions
One of the most important overall results of the project is that a clear positive correlation was found between symptoms of anorexia and symptoms of autism in all groups we examined, that is, in both patients and the community sample, and in both women and men. For example, people with an anorexia diagnosis had higher scores on the autism scale than people in the control group, and a person from the community sample with high scores on the anorexia scale usually also had high scores on the autism scale. These relationships applied both to general symptoms of autism (the sum of all subscales of the autism questionnaire) and specifically to social behavior (the subscales that distinguished difficulties in social interaction). The association also remained when we controlled for symptoms of compulsive behaviors, which are common in both anorexia and autism. However, the connection disappeared when we controlled for social anxiety. The conclusions we can draw from this finding are that the association between anorexia and autism is general and robust, and that a common factor behind the connection may be related to social interaction.
The second most important finding was that both symptoms of anorexia and symptoms of autism showed a negative relationship with brain volume in areas linked to social interaction, but only in women and not men. Here it was found that women who had either elevated symptoms of anorexia or autism had smaller brain volume in these areas. Using a statistical mediation analysis, we then found that the relationship between brain volume in these areas and symptoms of anorexia was mediated by the relationship with symptoms of autism. In other words, this statistical model suggests that reduced volume in social brain areas leads to symptoms of autism which in turn leads to symptoms of anorexia, rather than the reverse. This result strengthens the conclusion that difficulties in social interaction may be an underlying factor behind the association between anorexia and autism, which in turn is linked to how the brain processes social situations.
The third most important finding was that women who recovered from anorexia also had elevated symptoms of autism. This was true in both the community sample (in the participants who stated that they had previously had a diagnosis of anorexia) and in the follow-up of the group that we studied four years earlier and who then had anorexia. Here, the recovered participants in the community sample also had less volume in the brain areas linked to social function, while brain volume in the recovered participants in the follow-up group had been significantly increased. The conclusions we can draw here are that elevated symptoms of autism in anorexia seem to not be a result of starvation or caloric restriction. The results in the community sample also suggest that starvation does not cause the smaller volumes in the social brain areas. However, this conclusion should be taken with a large grain of salt as we obtained results that are partially contradictory, and more studies are needed to draw firm conclusions.
New research questions
The project has generated a large number of new exciting research questions. For example, we are now curious as to whether the connection between anorexia and autism is unique to these two conditions, or whether there is also a connection with e.g. ADHD and bulimia? Or between autism and bulimia? And what does the connection look like between eating disorders and neuropsychiatric symptoms in general? And how much of these connections can then be explained by the social factors we have focused on in this study? And, what other factors are important for these relationships, and how do the various factors interact? And how do genetic aspects come into play?
Another area that is important for future studies is the sex similarities and differences that the project discovered. The project was initially focused only on girls because diagnosed anorexia in boys is rare, but in the added community sample we found the same association between symptoms of autism and symptoms of eating disorders in men as well. In addition, we saw substantial sex differences in the brain, which raises a number of questions that future research can hopefully clear up.
Dissemination of results
The research has been disseminated in popular science formats in several productions of the interactive exhibition "Gissa hjärnan " and the workshop "Skär-i-hjärna", among others at the Science Festival in Gothenburg and at Universeum. In collaboration with Universeum, we are now also planning a larger exhibition about the brain with an estimated start in April 2023. Each participant in the study also received a small 3D-printed model of their own brain as well as images of cross-sections through the brain.
Research results have also been shared with treating clinics in the Västra Götaland region, including through a training day at Sahlgrenska University Hospital themed Autism and co-morbidity/differential diagnostics. Unfortunately, due to covid-19, planned information meetings for patients and relatives had to be cancelled.
The project has a website: www.nexa.nu. It will be updated with research results as they are published.
The project's results have also been disseminated in presentations at scientific conferences (see list below) and in the form of scientific manuscripts, prepared for publication in international scientifically assessed journals with Open Access. All articles will also be shared in pdf format in the open database Researchgate and on the study's website.
Conference presentations
S Cully & M Björnsdotter (2022) Does social cognitive brain volume mediate the link between autistic traits and eating pathology? Annual meeting for the Organization for Human Brain Mapping, Glasgow, UK
S Cully & M Björnsdotter (2022) Social cognitive brain volume indirectly predicts eating pathology via autistic traits, The XXVIIIth Annual Meeting of the Eating Disorders Research Society, Philadelphia, USA
M Björnsdotter (2020) Associations between eating disorder symptoms and autistic traits, 29th European Congress of Psychiatry, Madrid, Spain
Journal papers
S Cully et al., Social brain brain morphology mediates the link between and symptoms of anorexia (2023) (in preparation)
M Björnsdotter et al., Autistic traits in women recovered from anorexia nervosa - a 4 year follow-up study (2023) (in preparation)
S Cully et al., Associations between symptoms of anorexia nervosa and autistic traits in a large community sample (2023) (in preparation)
M Björnsdotter et al., Shared and distinct structural and functional brain alterations in autism spectrum disorder and anorexia nervosa (2024) (in preparation)
Alla artiklar publiceras i Open Access, och kommer delas fritt på Researchgate samt på studiens hemsida.
The purpose of this project was to characterize the neuropsychological link between anorexia nervosa and autism, with a specific focus on social processes. The project developed largely according to the plan, with some additions due to the covid-19 pandemic. We used magnetic resonance imaging to assess brain anatomy and function, and psychometric questionnaires and tests to examine behavior. We have investigated similarities and differences between patients diagnosed with anorexia and autism, and due to covid-19 limiting patient recruitment in clinics, we also included a large non-clinical community sample. In this community sample, we benefited from the fact that both eating disorders and autism are spectrum conditions and we could characterize the association between measurable symptoms of anorexia and symptoms of autism. In total, the project has analyzed data in over 350 participants. In addition, we supplemented the study with data in people with diagnosed anorexia and autism from large international collaborative projects.
The three most important results and conclusions
One of the most important overall results of the project is that a clear positive correlation was found between symptoms of anorexia and symptoms of autism in all groups we examined, that is, in both patients and the community sample, and in both women and men. For example, people with an anorexia diagnosis had higher scores on the autism scale than people in the control group, and a person from the community sample with high scores on the anorexia scale usually also had high scores on the autism scale. These relationships applied both to general symptoms of autism (the sum of all subscales of the autism questionnaire) and specifically to social behavior (the subscales that distinguished difficulties in social interaction). The association also remained when we controlled for symptoms of compulsive behaviors, which are common in both anorexia and autism. However, the connection disappeared when we controlled for social anxiety. The conclusions we can draw from this finding are that the association between anorexia and autism is general and robust, and that a common factor behind the connection may be related to social interaction.
The second most important finding was that both symptoms of anorexia and symptoms of autism showed a negative relationship with brain volume in areas linked to social interaction, but only in women and not men. Here it was found that women who had either elevated symptoms of anorexia or autism had smaller brain volume in these areas. Using a statistical mediation analysis, we then found that the relationship between brain volume in these areas and symptoms of anorexia was mediated by the relationship with symptoms of autism. In other words, this statistical model suggests that reduced volume in social brain areas leads to symptoms of autism which in turn leads to symptoms of anorexia, rather than the reverse. This result strengthens the conclusion that difficulties in social interaction may be an underlying factor behind the association between anorexia and autism, which in turn is linked to how the brain processes social situations.
The third most important finding was that women who recovered from anorexia also had elevated symptoms of autism. This was true in both the community sample (in the participants who stated that they had previously had a diagnosis of anorexia) and in the follow-up of the group that we studied four years earlier and who then had anorexia. Here, the recovered participants in the community sample also had less volume in the brain areas linked to social function, while brain volume in the recovered participants in the follow-up group had been significantly increased. The conclusions we can draw here are that elevated symptoms of autism in anorexia seem to not be a result of starvation or caloric restriction. The results in the community sample also suggest that starvation does not cause the smaller volumes in the social brain areas. However, this conclusion should be taken with a large grain of salt as we obtained results that are partially contradictory, and more studies are needed to draw firm conclusions.
New research questions
The project has generated a large number of new exciting research questions. For example, we are now curious as to whether the connection between anorexia and autism is unique to these two conditions, or whether there is also a connection with e.g. ADHD and bulimia? Or between autism and bulimia? And what does the connection look like between eating disorders and neuropsychiatric symptoms in general? And how much of these connections can then be explained by the social factors we have focused on in this study? And, what other factors are important for these relationships, and how do the various factors interact? And how do genetic aspects come into play?
Another area that is important for future studies is the sex similarities and differences that the project discovered. The project was initially focused only on girls because diagnosed anorexia in boys is rare, but in the added community sample we found the same association between symptoms of autism and symptoms of eating disorders in men as well. In addition, we saw substantial sex differences in the brain, which raises a number of questions that future research can hopefully clear up.
Dissemination of results
The research has been disseminated in popular science formats in several productions of the interactive exhibition "Gissa hjärnan " and the workshop "Skär-i-hjärna", among others at the Science Festival in Gothenburg and at Universeum. In collaboration with Universeum, we are now also planning a larger exhibition about the brain with an estimated start in April 2023. Each participant in the study also received a small 3D-printed model of their own brain as well as images of cross-sections through the brain.
Research results have also been shared with treating clinics in the Västra Götaland region, including through a training day at Sahlgrenska University Hospital themed Autism and co-morbidity/differential diagnostics. Unfortunately, due to covid-19, planned information meetings for patients and relatives had to be cancelled.
The project has a website: www.nexa.nu. It will be updated with research results as they are published.
The project's results have also been disseminated in presentations at scientific conferences (see list below) and in the form of scientific manuscripts, prepared for publication in international scientifically assessed journals with Open Access. All articles will also be shared in pdf format in the open database Researchgate and on the study's website.
Conference presentations
S Cully & M Björnsdotter (2022) Does social cognitive brain volume mediate the link between autistic traits and eating pathology? Annual meeting for the Organization for Human Brain Mapping, Glasgow, UK
S Cully & M Björnsdotter (2022) Social cognitive brain volume indirectly predicts eating pathology via autistic traits, The XXVIIIth Annual Meeting of the Eating Disorders Research Society, Philadelphia, USA
M Björnsdotter (2020) Associations between eating disorder symptoms and autistic traits, 29th European Congress of Psychiatry, Madrid, Spain
Journal papers
S Cully et al., Social brain brain morphology mediates the link between and symptoms of anorexia (2023) (in preparation)
M Björnsdotter et al., Autistic traits in women recovered from anorexia nervosa - a 4 year follow-up study (2023) (in preparation)
S Cully et al., Associations between symptoms of anorexia nervosa and autistic traits in a large community sample (2023) (in preparation)
M Björnsdotter et al., Shared and distinct structural and functional brain alterations in autism spectrum disorder and anorexia nervosa (2024) (in preparation)
Alla artiklar publiceras i Open Access, och kommer delas fritt på Researchgate samt på studiens hemsida.