Author: Madeleine Curtis
Curtis, Madeleine, 2024 Disordered Eating, Beyond Diagnoses: Classification, and Polygenic and Epigenetic Associations in the General Population, Flinders University, College of Education, Psychology and Social Work
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Disordered eating, encompassing both clinical eating disorders and disordered eating-related behaviours and cognitions, is associated with significant physical and psychological impairment and poor long-term health outcomes. There is a lack of research, however, on disordered eating as a broad phenotype, beyond clinical diagnoses. Thus, the overarching aim of this thesis was to advance current knowledge of disordered eating through investigating disordered eating classification, genomic risk, and epigenetic associations in the general population.
Chapter 2 consolidated research on physical and psychological impairments experienced by individuals with DSM-5 eating disorders. The meta-analyses demonstrated for the first time that the revisions made to eating disorder criteria in the DSM-5 still do not result in improved differentiation between other/unspecified eating disorders and full criteria eating disorders in terms of symptom severity. Findings highlight the clinical severity of other/unspecified eating disorders and support the critical need for research on the broader spectrum of disordered eating, which was the focus of the remaining studies in this thesis.
Molecular genetic research on eating disorders is progressing rapidly, however disordered eating as a broad phenotype has received little attention. With a shared genetic basis across different eating disorder presentations likely, Chapter 3 investigated whether polygenic risk scores (PRS) for AN predicted overall levels of disordered eating in the general population, or specific lifetime behaviours (avoidance of eating, objective bulimic episodes, self-induced vomiting, driven exercise). The AN PRS predicted all disordered eating outcomes, supporting potential future integration of AN PRS in early disordered eating risk identification, prevention, and intervention strategies.
Chapter 4 extended findings from Chapter 3 to investigate if parental expectations, criticism, conflict, or care, or weight-related peer teasing, moderated the relationship between AN PRS and disordered eating. Higher parental expectations and criticism, lower parental care, and increased weight-related peer teasing were associated with disordered eating. All environmental factors moderated the association between AN PRS and disordered eating by either further increasing risk (parental expectations, parental criticism, parental conflict, weight-related peer teasing) or lowering risk (parental care, parental criticism) for disordered eating phenotypes. This demonstrates the importance of both genetic and environmental influences and should inform personalised disordered eating interventions and strategies in the future.
Finally, Chapter 5 explored the relationship between disordered eating and epigenetic age acceleration, and the mediating role of BMI. Both global EDE-Q scores and restriction at age 14 were longitudinally associated with pace of ageing at age 17. The relationship between restriction and pace of ageing was partially mediated, and the relationship between global EDE-Q scores and pace of ageing was fully mediated through BMI. Findings indicated that third-generation epigenetic clocks may be useful in assessing the biological impact of disordered eating and underscore the potential importance of BMI in understanding the long-term health outcomes of disordered eating.
Together, findings of this thesis support the need for broader disordered eating classification and research to enable, in the long-term, potential integration of PRS and epigenetic variation with environmental influences for risk identification and early intervention, all aimed at improving prevention and health outcomes.
Keywords: disordered eating, eating disorder, polygenic risk, interaction, genetics, epigenetics
Subject: Psychology thesis
Thesis type: Doctor of Philosophy
Completed: 2024
School: College of Education, Psychology and Social Work
Supervisor: Sarah Cohen-Woods