Out of body illusion in anorexia nervosa

Anorexia nervosa (AN) is one of the most invasive psychosomatic disorders with
a relatively high mortality rate. In order to ensure successful treatment it is
crucial to understand the underlying mechanisms of AN. One of the central
symptoms of AN is a disturbed experience of the own body. To date, not all
aspects of body image disturbance have been investigated fully. Nevertheless,
research shows that body image disturbances appear to be the key to full
recovery of AN. Therefore the current study wil focus on bodily illusions and
body size experience.
In two of our previous studies we found that AN patients overestimate their
body size compared to healthy controls. However, after inducing a bodily
illusion (rubber hand illusion, body swap illusion) the amount of
overestimation in the AN group was reduced.
In our previous studies we focused on presenting another body (part) to
participants during bodily illusions. in the current study we want to
investigate whether giving participants a different view on their body in
virtual reality (Out of Body Illusion, OBI) reduces overestimation of body size
in the AN group as well. We expect that changing the perspective from which the
patients sees her own body will result in changes in body size experience.

The primary objective of this study is investigating whether AN patients and
healthy controls differ in how they estimate the size of their shoulders,
waist, and hips before and after induction of the OBI. We will specifically
investigate whether the percentage of misestimation at pre and post OBI differs
between AN patients and controls.

The secondary objective of the study is investigating whether the OBI does not
only affect visual estimates of body size, but also other measures of body
image.

Quasi-experimental research

It is not expected, but it is theoretically possible that participants
experience negative emotions during the study, for example in response to
induction of the OBI in which the participants has the illusonary experience of
looking at her body from a distance. However, the chance of experiencing
negative emotions is thought to be minimal, as before the experiment takes
place the participants will be informed about the procedures and what they can
expect during the experiment. From previous experience with (AN) studies we
learned that participants understand why certain methods are important for the
study, and that explaining these methods to participants reduces concerns. In
addition, this study will result in valuable insights in body image disturbance
in AN.