An international team has studied the genomes of more than 20,000 individuals, shedding light on the genetic links between eating disorders, mental illnesses and body weight regulation.
Eating disorders are highly complex, heritable psychiatric conditions. Estimates indicate that 4 in 10 people in Western Europe will experience one of these disorders at some point in their lives. Among them, the most well studied is anorexia nervosa. It is characterised by dangerously low body weight and extreme fear of gaining weight. In contrast, individuals with bulimia nervosa and binge-eating disorder have episodes of excessive overeating accompanied by a sense of loss of control. These individuals often in engage in compensatory behaviours to counteract the effects of binge eating.
Various twin and family studies over the past 30 years have shown that eating disorders are in fact heritable. The largest GWAS to date found eight genomic regions associated with anorexia nervosa. The study also found genetic correlations with OCD, schizophrenia, anxiety and major depressive disorder. This indicates that anorexia shares genetic risk variants with these phenotypes. Studies have also demonstrated a positive genetic correlation between anorexia and bulimia, indicating shared genetics. However, GWASs of bulimia have lacked sufficient sample sizes.
Exploring the genetic patterns
To explore the genetic similarities and differences between eating disorders, the team analysed the genomes of over 20,000 people. These genomes were taken from two large population-based studies in the UK: the UK Biobank and the Avon Longitudinal Study of Parents and Children. They conducted polygenic score analyses for 269 trait and disease outcomes to identify traits that are genetically associated with either anorexia, bulimia or binge-eating disorder.
Their results, published in the International Journal of Eating Disorders, showed that while there are great genetic similarities between these three disorders, there are also notable differences. For example, similarities were found in the association with psychiatric risk. All three disorders were found to share genetic risk with certain psychiatric disorders, particularly schizophrenia and depression. However, differences were also found in the association of body weight regulation. Their findings reveal that bulimia and binge-eating disorder had strong positive association with overweight and obesity variants. Whereas the direction of these associations in anorexia were reversed. This indicates that BMI-associated genomic variants are relevant for eating disorders but may act in opposite directions in anorexia compared to bulimia and binge-eating disorder.
These findings provide opportunity for translational research relevant to eating disorder phenotypes. They motivate a deeper investigation into the shared and unique genomic factors across the three primary eating disorders.
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