Anorexia nervosa (AN) is a confounding, debilitating disease characterized by pathological eating, obsession with body weight and thinness, intentional and drastic caloric restriction and energy expenditure to the point of emaciation resulting in a body mass < 80% of normal weight, adjusted for the individual’s age and height. Accordingly, AN is associated with serious cardio-metabolic disease, and thus has the highest mortality of any psychiatric disease. It is one of the major women’s diseases associated with death. Of course, AN can and does occur in men too.
Anorexia Nervosa Genetic Factors
Historically, anorexia nervosa was viewed as a disorder primarily influenced by sociocultural and non-genetic familial factors. After blaming diet-obsessed Western cultures, mothers, fear of oral impregnation, diets, advertisements and other factors, the bottom line is that the etiology of AN is not well understood. But more recently this perception has been challenged. Genetic studies have consistently demonstrated that AN is a heritable trait. Twin studies have underscored the contribution of genetic factors to the observed familial aggregation.
Recent novel analysis utilizing superior specificity has allowed geneticist to sequence single nucleotide polymorphisms (SNPs), via variants in minor allele frequencies, in order to identify genome-wide locus for anorexia nervosa on chromosome 12. This procedure eliminates confounding biases that inflate distribution of test statistics in previous genome-wide association studies. Using linkage disequilibrium (LD) analysis, these findings point to a robust phenotypical heritability from common variants, many of which are associated with other psychiatric disorders and metabolic abnormalities, including schizophrenia, OCD, neuroticism, abnormalities in body weight, insulin, glucose and lipid levels. In other words, anorexia nervosa is a complex, highly heritable phenotype that shares epigenetic variants with brain diseases and cardio-metabolic disorder.
Why Does This Matter?
Over the past 30 years, psychological pedagogy has strongly asserted that psychological and non-genetic familial and emotional stressors were primary causative factors of anorexia nervosa. Yet to date, psychotherapeutic treatment outcomes for anorexia nervosa are poor at best. As a result, families suffer unnecessarily from overwhelming fear, guilt, and sadness, while hoping beyond hope, that the next doctor or the next new treatment program might save their child and restore a modicum of peace from this insidious disease.
Although genetic research into the etiology and pathophysiology of anorexia nervosa is still in its infancy, it is vitally important that we affirm that this disease is genetically complex and heritable, involving multiple psychiatric and metabolic risk factors. Hopefully, this reconceptualization of anorexia nervosa will hasten commitment to further research and embolden our resolve to develop new therapeutic agents and treatment modalities to fight this dreadful disease.