Mirror, mirror, on the wall: During pandemics, how can self-perception research in people with eating disorders happen at all?

Background: 'Classic' embodiment illusions (e.g., the feeling of owning another person's hand) involves a three-way interaction between visual, proprioceptive, and tactile stimuli. These illusions have been studied in eating disorder (ED) populations given the potential implications for better understanding and improving body image concerns. Recently, several studies have employed 'tactile-reduced' methods mainly relying on the integration of visual and proprioceptive information to induce embodiment illusions in non-ED populations. To date, there has been no substantial review of these tactile-reduced approaches to consider their potential research and clinical utility in ED populations. Method: This review sought to examine and integrate studies across three areas. Firstly, those that employed tactile-reduced embodiment techniques in non-ED populations. Secondly, those that used classic embodiment techniques to compare whether ED and non-ED populations differ in their susceptibility to embodiment. Thirdly, studies that investigated whether experiencing classic or tactile-reduced embodiment techniques can improve image-related concerns. Results: For the first aim five studies were identified, all of which found that tactile-reduced methods consistently induced embodiment illusions in non-ED individuals. For the second aim, seven studies comparing ED and non-ED samples were found. ED patients were more susceptible to embodiment than non-ED samples in four studies, less susceptible in one study, and equally susceptible in two studies. Finally, for aim three, amongst the seven studies that used classic or tactile-reduced embodiment methods in ED populations, six reported improvements in self-perception (i.e., reduced body size overestimation, decreased body dissatisfaction and fear of gaining weight). Conclusions: Along with the classic approach, tactile-reduced embodiment approaches have implications for ED research and clinical practice, particularly for situations when face-to-face contact with people are restricted. Suggestions are provided for future researchers who wish to ensure best practice for planning embodiment research involving classic and tactile-reduced approaches. Plain English summary: Embodiment illusions involve the temporary experience of owning another person's body or body parts. These illusions have been studied in people with eating disorders (EDs) as a means for (i) better understanding their self-perception issues (e.g., they tend to see their own appearance as being too big), and (ii) improving these self-perception issues (i.e., does experiencing embodiment reduce distortions involving body size?). 'Classic' embodiment illusions typically require participants to simultaneously experience visual, proprioceptive, and tactile sensory stimulation. However, COVID -19 pandemic restrictions have limited research in face-to-face settings which poses a challenge for the classic approach, mainly in relation to tactile input which would usually be provided by a researcher. A 'tactile-reduced' approach for eliciting embodiment illusions would, therefore, enable this field of research to continue, which in turn may benefit people with EDs. While several studies in non-clinical populations have demonstrated the effectiveness of a tactile-reduced approach, understanding surrounding this approach in ED populations is lacking. In this review, we offer a prospective set of suggestions regarding how tactile-reduced embodiment may be conducted with ED populations, both in terms of better understanding their (problematic) self-perception, and how such concerns may be improved. [ABSTRACT FROM AUTHOR]