Okay, so there hasn’t been a post in a while, no thanks to my dissertation – an 8,000 word essay on “Is there a neuro-cognitive basis of body dysmorphia in anorexia nervosa”. While I doubt many people would actually want to read the whole thing, this is a fascinating topic, so this post will be a (very) shortened version – hope you enjoy!
Firstly, if you’d like more information about anorexia and other eating disorders, check out my previous post, which gives a pretty good background.
So what is body dysmorphia? Basically, I was trying to find out if there was any abnormality in the brain which causes sufferers of anorexia to feel as though they are fat, when in fact they are seriously underweight. It is important to find this out, as if body dysmorphia is not treated in anorexic patients, it could prevent full recovery by maintaining restricted eating patterns (Heilbrun & Friedburg, 1990). Having body dysmorphia also makes suffering from anorexia more likely, therefore early intervention could prevent people from developing the disorder.
The Multidimensional Model of Body Dysmorphia
I focused on evaluating the multidimensional model of body dysmorphia in anorexia, which was proposed by Cash and Deagle (1997). This states that there are two main processes underlying body dysmorphia:
– Perceptive: involves deficits in perceptual processing of body stimuli, and less activation in areas of the brain involved in perceiving body image.
– Attitudinal: split into affective and cognitive components. The affective component states that anorexia sufferers show more activation of the amygdala to body stimuli, which suggests increased emotional involvement and possibly a fear response to body-related stimuli. The cognitive component states that sufferers overestimate their body size due to inaccurate body schema.
In order to find out whether anorexic patients have abnormal perceptual body processing, you first need to look at how healthy people process their body image. Downing et al (2001) found that the extrastriate body area (EBA) in the posterior and inferior temporal sulcus is active during body shape perception in the healthy population. Another area – the fusiform body area (FBA) has been identified (Taylor and Downing, 2011). These are shown in the image below:
These areas are thought to detect changes in body shape (Aleong and Paus, 2009), which could explain why anorexic patients don’t recognise their thinner body shape. The first study which showed that these areas could be dysfunction in anorexia was carried out by Uher et al (2005). They used fMRI to measure neural activity while healthy, anorexia nervosa and bulimia nervosa participants were presented with line drawings of overweight, underweight or normal female bodies. They found less activity in the EBA in anorexic women, which suggests a functional abnormality in this area.
The two key pieces of evidence for this are increased amygdala activation to body images (Seeger et al, 2002), and more anxiety in AN patients when shown body images, compared to controls (Friedrich et al, 2006). Seeger et al found that anorexic patients show a more activation of the amygdala when they are presented with distorted pictures of their own body. This suggests a higher emotional involvement in body images as the amygdala has been shown to be involved in emotion processing (e.g. Birbaumer et al, 1998).Friedrich et al found that AN patients show more anxiety than healthy controls when shown pictures of thin models, which again suggests higher levels of emotion caused by body images.
This states that AN patients have unrealistic body schema, which causes them to view themselves as being fatter than they actually are. But why do AN have larger body schema? One theory is that it could be caused by rapid weight loss, meaning the body schema is not updated. This was first shown by Guardia et al (2010), who, as body schema are involved in action, investigated how anorexic patients estimate body size in relation to actions. This study used a doorway aperture method – participants had to imagine whether or not they could walk through an doorway of varying sizes at normal speed and without turning sideways. They found that anorexic patients significantly overestimated their shoulder width compared to controls, which suggests a dysfunctional body schema.
Another study (Metral et al, 2014) found that anorexic patients act like they are fatter than they are too. This used the same method as the one described above. However, instead of just imagining whether or not they could pass through an aperture, participants had to then actually carry out that action.
Therefore, it is likely that a combination of all these factors causes patients with anorexia to view themselves as being fatter than they actually are, and continue to restrict their diet as they believe they need to lose weight. It is therefore vitally important to break this cycle by treating body dysmorphia, in order to allow anorexic patients to view their true body size, and enable them to make a full recovery.
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