Genetics of anorexia nervosa: an overview of genome-wide association studies and emerging biological links

Two identical twin pairs discordant for longstanding anorexia nervosa and OSFED: lived experience accounts of eating disorder and recovery processes

Research into the risk of anorexia nervosa (AN) has examined twin pairs to further the understanding of the contributions of genetics, trait inheritance, and environmental factors to eating disorder (ED) development. Investigations of twin experiences of EDs have been biologically-based and have not considered the qualitative, phenomenological aspects of twin experiences. A gap in the literature exists regarding understanding of discordant twins with EDs. This research was developed in response, with the aim to deepen understanding of AN in discordant twins and to create novel ideas for further research and testing. The case studies presented in this article provide lived experience insights of two identical discordant twin pairs: one twin pair discordant for longstanding AN and one twin pair discordant for 'atypical' AN (the twin with AN has recovered). The perspectives and experiences of each co-twin (one with AN and one without) explore a number of factors that may have contributed to twin discordance in these cases, and how each twin has responded to the impact of AN in their lives. Through use of first-person accounts in case study presentation, this article centres social justice values of lived experience leadership and involvement in research. This article aims to extend current knowledge and understanding of EDs in discordant twins, particularly regarding risk for ED development, ED duration, diagnosis and treatment, and recovery processes.

Inclusion of the severe and enduring anorexia nervosa phenotype in genetics research: a scoping review

BACKGROUND

Anorexia nervosa has one of the highest mortality rates of all mental illnesses. For those who survive, less than 70% fully recover, with many going on to develop a more severe and enduring phenotype. Research now suggests that genetics plays a role in the development and persistence of anorexia nervosa. Inclusion of participants with more severe and enduring illness in genetics studies of anorexia nervosa is critical.

OBJECTIVE

The primary goal of this review was to assess the inclusion of participants meeting the criteria for the severe enduring anorexia nervosa phenotype in genetics research by (1) identifying the most widely used defining criteria for severe enduring anorexia nervosa and (2) performing a review of the genetics literature to assess the inclusion of participants meeting the identified criteria.

METHODS

Searches of the genetics literature from 2012 to 2023 were performed in the PubMed, PsycINFO, and Web of Science databases. Publications were selected per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). The criteria used to define the severe and enduring anorexia nervosa phenotype were derived by how often they were used in the literature since 2017. The publications identified through the literature search were then assessed for inclusion of participants meeting these criteria.

RESULTS

most prevalent criteria used to define severe enduring anorexia nervosa in the literature were an illness duration of ≥ 7 years, lack of positive response to at least two previous evidence-based treatments, a body mass index meeting the Diagnostic and Statistical Manual of Mental Disorders-5 for extreme anorexia nervosa, and an assessment of psychological and/or behavioral severity indicating a significant impact on quality of life. There was a lack of consistent identification and inclusion of those meeting the criteria for severe enduring anorexia nervosa in the genetics literature.

DISCUSSION

This lack of consistent identification and inclusion of patients with severe enduring anorexia nervosa in genetics research has the potential to hamper the isolation of risk loci and the development of new, more effective treatment options for patients with anorexia nervosa.

Eating disorder psychopathology, psychiatric impairment, and symptom frequency of atypical anorexia nervosa versus anorexia nervosa: A systematic review and meta-analysis

OBJECTIVES

Restrictive eating disorders (EDs) occur across the weight spectrum, but historically more focus has been given to anorexia nervosa (AN) than atypical anorexia nervosa (atypAN). AtypAN's relegation to a diagnosis in the "other specified feeding and eating disorder" (OSFED) category and paucity of research surrounding atypAN invariably implies a less clinically severe ED. However, a growing body of research has begun to question the assumption that atypAN is less severe than AN. The current review and meta-analysis aimed to provide a comprehensive review to compare atypAN and AN on measures of eating disorder psychopathology, impairment, and symptom frequency to test whether atypAN is truly less clinically severe than AN.

METHODS

Twenty articles that reported on atypAN and AN for at least one of the variables of interest were retrieved from PsycInfo, PubMed, and ProQuest.

RESULTS

For eating-disorder psychopathology, results indicated that differences were nonsignificant for most indicators; however, atypAN was associated with significantly higher shape concern, weight concern, drive for thinness, body dissatisfaction, and overall eating-disorder psychopathology than AN. Results indicated that atypAN and AN did not significantly differ on clinical impairment or the frequency of inappropriate compensatory behaviors, whereas there was a significantly higher frequency of objective binge episodes in AN (vs. atypAN).

DISCUSSION

Overall, findings indicated that, in contrast to the current classification system, atypAN and AN were not clinically distinct. Results underscore the need for equal access to treatment and equal insurance coverage for restrictive EDs across the weight spectrum.

PUBLIC SIGNIFICANCE

The current meta-analysis found that atypAN was associated with higher drive for thinness, body dissatisfaction, shape concern, weight concern, and overall eating-disorder psychopathology than AN; whereas AN was associated with higher frequency of objective binge eating. Individuals with AN and atypAN did not differ on psychiatric impairment, quality-of-life, or frequency of compensatory behaviors, highlighting the need for equal access to care for restrictive EDs across the weight spectrum.

Polyunsaturated fatty acids and risk of anorexia nervosa: A Mendelian randomization study

PURPOSE

Observational studies have suggested that polyunsaturated fatty acids (PUFAs) decrease the risk of anorexia nervosa (AN). In the present study, we examined this hypothesis using a Mendelian randomization analysis.

METHODS

We used summary statistics for single-nucleotide polymorphisms associated with plasma levels of n-6 (linoleic acid and arachidonic acid) and n-3 PUFAs (alpha-linolenic acid, eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid) and the corresponding data for AN from a genome-wide association meta-analysis of 72,517 individuals (16,992 diagnosed AN cases and 55,525 controls).

RESULTS

None of the genetically predicted PUFAs were significantly associated with the risk of AN; odds ratios (95 % confidence interval) per 1 standard deviation increase in PUFA levels were 1.03 (0.98, 1.08) for linoleic acid, 0.99 (0.96, 1.03) for arachidonic acid, 1.03 (0.94, 1.12) for alpha-linolenic acid, 0.98 (0.90, 1.08) for eicosapentaenoic acid, 0.96 (0.91, 1.02) for docosapentaenoic acid, and 1.01 (0.90, 1.36) for docosahexaenoic acid.

LIMITATION

Only two types of fatty acids (LA and DPA) can be used for pleiotropy tests using the MR-Egger intercept test.

CONCLUSION

This study does not support the hypothesis that PUFAs decrease the risk of AN.

Anorexia nervosa and autoimmune comorbidities: A bidirectional route?

Immunological dysfunctions in eating disorders have recently gained increasing scientific attention. Furthermore, the reciprocal association between anorexia and autoimmune diseases is of particular interest and suggests a role of autoimmunity in the pathogenesis of eating disorders. Anorexia nervosa (AN) and autoimmune diseases are linked by a bidirectional relationship based on common immunopathological mechanisms. In this review, in addition to reporting the numerous cases described in which autoimmune disorders are associated with anorexia or vice versa, we summarize the many aspects of this relationship between the immune system (IS) and AN. We describe how the microbiota affects the IS, disrupts gut-brain communication, and possibly triggers eating disorders. We also describe the shared immunological pathways of autoimmune and eating disorders and in particular the occurrence of disrupted T cell tolerance and autoantibodies in AN. The described observations represent the starting point for possible, future research directions.