 Twin studies have found a slight instances of genetic variance when considering the different criterion of both anorexia nervosa and bulimia nervosa as endophenotypes contributing to the disorders as a whole.A genetic link has been found on chromosome 1 in multiple family members of an individual with anorexia nervosa.An individual who is a first degree relative of someone who has had or currently has an eating disorder is seven to twelve times more likely to have an eating disorder themselves.