Anorexia nervosa, bulimia nervosa, and binge-eating disorder are the most common among eating disorders. Even though it affects 4 out of 10 people in Western Europe, the question about how these disorders develop had been neglected until recent years when researchers examined the genetic basis of anorexia nervosa. These studies focused on identifying the predisposing genetic markers for anorexia nervosa, which are shared with other psychiatric disorders as well. They have found a genetic association between a high risk of anorexia nervosa and a low risk of obesity. However, there had been next to no genome studies of other eating disorders, such as bulimia nervosa and binge-eating disorder. Thus, a study was conducted with the goal of understanding similarities and differences between genetic bases of anorexia nervosa, bulimia nervosa, and binge-eating disorder, and other psychiatric disorders. This study has been published in the International Journal of Eating Disorders and it analyzed the genomes of more than 20,000 people in the UK.
The researchers in this study used the participants’ basic health data, such as weight, age, etc. as well as responses to health questionnaires that gathered information about their eating disorder history and possible psychiatric disorders. They analyzed and calculated more than 250 polygenic scores for each person including scores for psychiatric disorders (such as schizophrenia and obsessive-compulsive disorder) and metabolic and physical traits (such as insulin sensitivity, obesity, and BMI). The research team then proceeded to examine the associations between the polygenic scores (represented as genetic liability to psychiatric disorders, metabolic and physical traits) and eating disorders.
What does the research show?
The researches showed that there are great genetic similarities between the three eating disorders, but that there are also some notable differences to be considered.
The main similarities between eating disorders are the ones regarding their association with psychiatric risk. That implies that anorexia nervosa, bulimia nervosa, and binge-eating disorder have a strong psychiatric component. They all share genetic risk with psychiatric disorders, particularly ones for schizophrenia and depression. Going even more in-depth, psychiatric polygenic scores were associated with particular disordered-eating behaviors and cognitions. Weight and shape concerns, as well as body dissatisfaction, were associated with the major depressive polygenic score. This suggests that individuals with a genetic propensity for depressive symptoms may perceive their bodies more negatively.
When it comes to differences, the main one considers the associated genetics of body weight regulation. Research shows that bulima nervosa and binge-eating disorder are linked to a high risk of obesity and high BMI, whereas that is not true when it comes to anorexia nervosa. Thus, the determining factor that pushes people who have similar psychiatric genetic risk towards different eating disorders might be a genetic predisposition to being a heavy weight versus a light weight. Nadia Micali, who has directed this study, explains that the metabolic and physical component is what might direct a person towards either anorexia nervosa or bulimia nervosa and binge-eating disorder. Other than that, this study confirmed the genetic relationship between binge-eating disorder and ADHD (attention deficit hyperactivity disorder) that has been observed in previous studies. A common trait linked to this relationship is high impulsivity, shared by the two disorders.
This study highlighted genetic patterns in body weight regulation that provides a new understanding of the genetics underlying eating disorders and their differences regarding genetic marking. This is a big step leading toward a better understanding of the development of eating disorders.