As a whole, eating disorders have been characterised as having the following key features: a persistent over concern with body size and shape; and weight control behaviours such as fasting, exercise, and self-induced vomiting. However, there tends to be a blurred line between those that do and do not meet diagnostic thresholds as the level of psychological distress is comparably similar. This study examined whether psychological inflexibility (from an Acceptance and Commitment Therapy perspective) was associated with eating disorders and whether it mediated the relationship between childhood abuse and invalidation and eating disorders. This was considered to be important because high rates of abuse have consistently been found in this population, yet not everyone goes on to develop an eating disorder. In addition, the role of emotional abuse has been largely neglected. A clinical sample of 190 participants with a clinical or subclinical eating disorder were recruited from eating disorder charities and support forums; they completed a range of questionnaires measuring experiences of abuse and maternal/paternal emotional invalidation in childhood, current levels of cognitive fusion and experiential avoidance and current levels of eating pathology. The sample was split into three groups based on their Eating Disorder Risk Composite scores: elevated, typical and low clinical range. It was found that those in the elevated clinical range (most severe eating pathology) had the poorest emotional processing and significantly higher levels of psychological inflexibility, thought-shape-fusion, depression and anxiety than those in the low clinical range (least severe eating pathology). In terms of predicting current levels of eating pathology, three variables emerged as significant predictors: emotional processing, thought-shape fusion and depression. In terms of predicting current levels of psychological inflexibility, five variables emerged as significant predictors: childhood emotional abuse, emotional processing, thought-shape-fusion, depression and anxiety. The results add novel findings to the literature regarding the role of early experiences on the development of psychological inflexibility, and the role of psychological inflexibility in the maintenance of eating pathology and psychological distress. Clinical implications of these findings in relation to assessment, formulation, intervention and prevention are discussed.

L'idée que les souches de rongeurs de laboratoire ne soient pas des modèles idéaux pour la recherche sur le vieillissement n’est pas nouvelle. Pourtant, l’attitude des chercheurs face à l’introduction d’animaux de type sauvage dans leurs travaux demeure frileuse bien que ces derniers apporteraient une solution adéquate pour l’étude d’un processus aussi complexe et multifactoriel que le vieillissement et permettraient d’intégrer les traits d’histoire de vie des individus afin de rendre compte de façon pertinente des changements liés à l’âge. Chez la souris glaneuse, le report de l’âge de première reproduction des animaux juvéniles hivernants conduit à la création de deux cohortes. Ces deux groupes d’animaux devront, à un âge plus ou moins avancé, explorer des environnements anxiogènes et faire face à des compétiteurs lors de leur dispersion, se reproduire et élever leur progéniture qui devra à son tour disperser. L’objectif de cette thèse est d’étudier les conséquences émotionnelles et sociales du vieillissement qui pourraient influencer les stratégies comportementales de ce rongeur de type sauvage. Ce travail s’ouvre également sur des thématiques d’actualité dans le domaine de la biogérontologie. Notre étude montre qu’à l’instar de celles réalisées chez l’Homme, le niveau d’anxiété d’un individu peut être déterminé par son âge mais aussi par l’âge de ses parents. L’âge de mise en couple va quant à lui influencer certaines stratégies liées à la reproduction comme la latence d’accouplement ou l’effort parental fourni par les mères et les pères et va conditionner l’apparition des premiers signes de sénescence reproductive. Enfin, cette étude dévoile que la durée de vie reproductive d’un couple monogame pourrait être un facteur renforçateur des liens qui unissent un mâle à sa partenaire. / The idea that standard laboratory rodents may not be an ideal model for aging research is not new. Nonetheless, the researcher's attitude toward using wild-type species remains cautious although these animals would make a suitable solution to study a process as complex and multifaceted as aging, and would allow to incorporate the life history traits of individuals to reflect appropriately age-related changes. In the mound-building mouse, the delay of the age of first reproduction of over wintering juvenile animals leads to the establishment of two cohorts. These two groups of animals have to, at more or less advanced ages, explore anxiogenic environnements and face competitors during dispersal, reproduce and raise their offspring wich will in turn disperse. The aim of this thesis is to study the emotional and social consequences of aging that could influence the behavioral strategies in this wild-type rodent focusing on current issues in the biogerontogical field. Our study shows that, like in humans, the anxiety level of an individual can be determined by its own age but also by the age of its parents at conception. For its part, the age at pairing influences reproduction-related strategies as the latency of first reproduction or parental effort provided by mothers and fathers and affects the appearence of the first signs of reproductive senescence. Finally, this work reveals that the duration of pairing could strengthen the social bond between a male and its partner in a monogamous species.