An investigation of the bodily self in eating disorders
The overall objective of this thesis was to examine whether individuals affected with an eating disorder (ED) have an altered experience of the bodily self in comparison to healthy control (HC) individuals. The secondary objective was to assess whether this hypothesised disturbance could be a state or trait phenomenon. This thesis proposes a transdiagnostic biopsychosocial model of the bodily self in EDs. The first three studies of the thesis used the rubber hand illusion (RHI) paradigm, which involves the illusion of ownership of a fake hand, to examine the proposed model. In the first study, it was found that individuals with an ED (n = 78) experienced the RHI (both perceptually and cognitively) significantly more strongly than the HC participants (n = 61). Individual differences in the experience of the RHI were significantly related to ED psychopathology, and the experience of the RHI was significantly predicted by interoceptive deficits and self-objectification after controlling for other ED and general psychopathology constructs. The second study extended on this study to examine whether these findings indicate a state or trait disturbance, by examining the RHI in individuals who had recovered from an ED (n = 28). Recovered individuals were intermediate to the acutely ill and HC group in the perceptual domain, whereas the recovered individuals were similar to acutely ill individuals in the cognitive domain, suggestive of a trait disturbance. The third study examined the effect of emotional distress on the experience of the bodily self as indexed by a modified version of the RHI task including an emotion induction component (e-RHI task). Emotional distress (whether in the form of body dissatisfaction or general distress) was not found to significantly alter the experience of the bodily self in those with an ED relative to HC individuals. The fourth study took a different methodological approach from the previous three studies and used a heartbeat detection task (HBDT) to focus specifically on interoception. The findings did not demonstrate significant differences between the ED and HC groups on interoceptive sensitivity as indexed by the HBDT. However, the HBDT did not appear to be a valid measure in this sample as floor effects were demonstrated. Overall, these findings provided preliminary support for the proposed model of an altered experience of the bodily self in individuals with an ED and the correlates of this disturbed bodily self. The findings from using the RHI task indicated an increased malleability of the bodily self in acutely affected individuals, with some evidence that this is a trait phenomenon also present in individuals recovered from an ED. More specifically, these studies provide evidence that heightened sensitivity to visual information about the body and reduced somatosensory information processing of the body are present in individuals with an ED as well as in recovered individuals, and are suggestive of a trait phenomenon. This thesis identifies the need for further research in this area, with the ultimate aim of translating these findings into clinical approaches for addressing body disturbances.
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