Rosiel Elwyn

Eating disorders (EDs) are complex conditions that significantly affect quality of life and often co-occur with other medical and psychiatric diagnoses. Anorexia Nervosa (AN), a severe ED, involves multiple aetiological factors—genetic, metabolic, neurocognitive, psychological, and socio-cultural—and is characterised by disturbances in eating, appetite, and food intake (including low food intake and behaviours that disrupt digestion such as purging), body image disturbance, malnutrition and low body weight, and high risks of co-occurring conditions, medical complications, and mortality. This thesis centres Lived Experience (LE) perspectives to explore ED understandings, highlighting nuances in treatment and recovery. The first two papers focus on conceptual and ethical factors in understanding of illness staging and recovery in AN, using lived experience perspectives and autoethnography. The third and fourth papers focus on the contribution of trauma to AN aetiology, and trauma as a maintaining factor. The third paper uses lived experience collective autoethnography and thematic analysis to explore comprehensive factors related to the discordant development of AN in twins, such as differing levels of early life stress and trauma exposure. The fourth paper is a poetic mediation as a lived experience method, which highlights how trauma may be unaddressed in AN treatment, and how ED treatment may be traumatic itself, compounding trauma-AN interrelationships and illness severity. Building on lived experience methods and the contributions of trauma to AN aetiology, the fifth and sixth chapters centre on AN neurobiology, with a focus on trauma, and its impact on key neurobiological functions, including the gut microbiome, and glutamatergic system. The fifth paper, a systematic review, examines shared and unique microbial taxa that may characterise or contribute to AN with or without exposure to adversity and/or PTSD. The sixth chapter is an exploratory case series of young women with AN and trauma exposure (SIGNET pilot study). The study examines the neurobiological and mental health factors related to AN, including their gut microbiome profiles, metabolic glutamatergic biosynthesis pathways, cognitive function, suicidality, interoception, levels of trauma exposure, and ED severity. The seventh and eighth papers focus on the need for personalised treatment and treatment innovation. The seventh paper explores the need for trauma-responsive, integrated treatment for longstanding AN and co-occurring conditions (i.e., psychosis). Using a lived experience-authored case study, this article emphasises how PTSD and complex PTSD can interact with AN symptoms and symptoms of co-occurring conditions. The final paper is a narrative review that presents the theory for a novel, neurobiologically informed treatment for AN involving ketamine and zinc. This treatment is proposed for individuals with trauma-associated AN who may not have responded to first-line treatments and may have a longstanding illness duration, with implications for the gut microbiome as a key factor in treatment response. Together, this thesis addresses multiple gaps in ED research, particularly in conceptualisation and understanding of longstanding AN, its aetiology and phenomenology, and the contributions of trauma. It integrates lived experience phenomenology and methods to advance conceptual understanding of AN (i.e., illness staging and recovery) and neurobiology (i.e., trauma, treatment non-response). Using multiple approaches, this work examines several key constructs important to longstanding AN phenomenology and neurobiology, including conceptualisations and ethics of prognosis, treatment non-response, and terminality, the
impact of trauma on AN aetiology and treatment non-response, the contribution of iatrogenic harm to compounded trauma and treatment experiences, the role of the gut microbiome as a mechanism in AN and trauma symptoms, the critical need for lived experience knowledge to advance ED research, and the need for integrated, trauma-responsive, personalised treatment.