Eating Disorders Information (EDI)

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Research

A genetic link to eating disorders?

Posted by a.marlow on October 7, 2012 at 5:00 AM Comments comments (0)

Two articles in recent editions of the International Journal of Eating Disorders paint us a very interesting, but also very puzzling, picture of the roles genes might play in the formation of eating disorders.


First, the positive role they might play: Soltenberg et al. in their study found that women who had a specific variant of the serotonin transporter gene SLC6A4 were more likely to respond to childhood trauma by developing eating problems in later life. (For those who don't know, serotonin is a brain chemical that is believed to regulate appetetite and mood, and whose abnormal functioning has been implicated in the formation and experience of eating disorders).


So far, so good- but another study by Munn-Chernoff et al. found, in contrast to the above referenced study, that there was no significant correlation between any variant of the SLC6A4 gene and either binge-eating or body weight concern.


So how can we reconcile these two seemingly conflicting studies? In reality, it is not that hard. Firstly, we need to consider that they were both looking at different things: Soltenberg et al. had a more general definition of eating problems, while Munn-Chernoff et al. were looking specifically at binge-eating and body weight concern. It is entirely possible that, had the latter group been looking for links with other kinds of disordered eating behaviour (such as the self-starvation shown by anorexics), they would have found a correlation.


Secondly, for what it's worth, both studies also looked at slightly different variants of the SLC6A4 gene. Soltenberg et al. focused their study on one particular variation of this gene (or 'allele*'), while Munn-Chernoff et al. conducted a more comprehensive study looking at seven different 'polymorphisms**' of this gene. You might expect, then, that the latter study would have more comprehensive results, and we can probably say that it did- but when saying that, it is important to remember the points made in the paragraph above about what specifically Munn-Chernoff et al. were looking for.


The picture that emerges, then, is a complicated one: which variant of the SLC6A4 gene you have can affect whether you contract an eating disorder later in life; however, this gene is not linked to either binge-eating or body image concern and only really determines how you'll react to childhood experiences, rather than completely determining the future state of your mental health.


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Flummoxed by some of the terms in this blog post? Don't worry, so am I. I had to look these terms up:


allele: the term 'allele' refers to an alternative form of a gene.


polymorphism: in genetics, "genotype" refers to the instructions passed down in the genetic code, while "phenotype" refers to the actual behaviour and traits exhibited by the creature that has those genes. Genotype is thus determined only by genes, while phenotype is determined by genetic and environmental factors. Here, a different "polymorphism" of the SLC6A4 gene would refer to a different phenotype of that gene i.e. different observable traits in different people carrying the same gene. When a polymorphism is genetic, as it seems to be here, the different behaviour results from an alteration in the gene itself.


I'll freely admit that genetics is not my speciality, so if I've got some of this wrong, please do correct me in the comments section.


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References:

Munn-Chernoff, M. A. et al., 2012. "Examining associations between disordered eating and serotonin transporter gene polymorphisms", International Journal of Eating Disorders, 45(4), 556-561

Soltenberg, S., et al., 2012. "Association between the serotonin transporter triallelic genotype and eating problems is moderated by the experience of childhood trauma in women", International Journal of Eating Disorders, 45(4), 492-500