Researchers from the Karolinska Institutet and the University of North Carolina School of Medicine have found that the eating disorder ARFID (avoidant restrictive food intake disorder) is highly heritable. The paper, published in JAMA Psychiatry, could improve our understanding of the underlying causes of the disorder and aid the development of better treatment options.
First classified as an eating disorder in 2013, ARFID is estimated to affect around 1-5% of the world’s population. It is characterised by an extremely low intake of food and is often driven by sensory aversion to certain foods or traumatic eating experiences that lead to phobias. This is very different to other eating disorders such as anorexia which are driven by factors such as body dysmorphia. Moreover, whilst other eating disorders disproportionately affect girls and women, ARFID is seen in both genders equally.
As you might imagine, the condition often leads to malnutrition and can have a serious impact on a person’s quality of life and health. Unlike many other eating disorders, the condition usually develops in childhood and can be extremely distressing to both the child and their parents. Despite the serious implications associated with ARFID, very little is actually known about the underlying causes of this disease, meaning treatments are few and far between.
To gain a better understanding of the role genetic factors play in the development of the disease, Lisa Dinkler (postdoctoral researcher at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet) and her team turned to a tried and tested method – twin studies.
As other eating disorders have already been strongly linked to genetics, the team deduced that ARFID would show a similar level of heritability. To test their theory, they used data from the Swedish Twin Registry (which includes over 34,000 twins born between 1992 and 2010) to study the influence of genetics and the environment on the onset of disease.
“We know that identical twins share all genes and that fraternal twins share about half of the genes that make people different. When we then see that a certain character trait is more common in monozygotic twin pairs than in dizygotic twin pairs, it is an indication that there is a genetic influence. We can then estimate the degree to which a character trait is influenced by the genes,” said Dr. Dinkler.
First, they identified children with ARFID by checking parental questionnaires and registered clinical diagnoses. In total, 682 children between 6-12 years of age were selected for the study.
They found that heritability was 70-85%. This means ARFID shows a higher heritability than that of anorexia nervosa (48-74%), bulimia nervosa (55-61%), and binge-eating disorder (39-57%), suggesting that ARFID might be the most heritable eating disorder.
“This study suggests that ARFID is highly heritable. The genetic component is higher than that of other eating disorders and on par with that of neuropsychiatric disorders such as autism and ADHD,” added Dr. Dinkler. In comparison, the heritability of autism is estimated to be 79-84%, and that of ADHD is 76-89%. This means ARFID is one of the most heritable mental health conditions.
There are a lot of potentially beneficial future implications for this research. Firstly, research such as this helps to greatly reduce the stigma around mental health disorders like ARFID and can aid parents in better coping with this challenging disease. On the other hand, the study highlights that the condition is not 100% down to your genetics – traumatic experiences with food can certainly trigger the disorder and it can only help parents to be aware of this.
The team aims to conduct more research in the future to aid the development of treatments that tackle not just the symptoms, but the underlying causes of ARFID. They also want to understand the extent to which ARFID is linked with other psychiatric diagnoses such as anxiety. “We will use twin studies to test the extent to which ARFID shares underlying genetic and environmental factors with these conditions,” added Dr. Dinkler.