Unhappy young Caucasian woman does not want to eat vegetables and does not like the bitter taste of vegetables.
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A new twin study of the relatively new eating disorder called Avoidant/Restrictive Food Intake Disorder (ARFID) is strongly influenced by a person’s genetics according to research published recently in JAMA Psychiatry by researchers at the Karolinska Institutet.

Unlike anorexia nervosa in which the person has a distorted perception of their weight and fears gaining weight, ARFID is characterized by patients avoiding certain types of food because of the characteristics or appearance of food, sensory discomfort from consuming the food, the fear of choking, fear of food poisoning, or a lack of appetite. The eating disorder affects between one and five percent of the population and can lead to serious complications including malnutrition and nutritional deficiencies.

The specific diagnosis of ARFID is only about 10 years old. In 2013, it was included in the Diagnostic and Statistical Manual of Mental Disorders, DSM-5, and was only added this year to the World Health Organization’s diagnostic manual ICD.

To find out the role played by genetic factors in ARFID, researchers at the Karolinska Institutet collected a cohort of nearly 17,000 pairs of twins born in Sweden between 1992 and 2010 to participate in the study. From that number, the investigators identified 682 children between the ages of six and 12 years old with ARFID. The twin method was used for this study to determine the influences of genes and the environment on the onset of the diseases.

“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 trait is more common in both members of identical twin pairs than in fraternal twin pairs, it is an indication that there is a genetic influence. We can then estimate the degree to which a trait is influenced by genetic factors,” said Lisa Dinkler a post-doctoral researcher in the Centre for Eating Disorders Innovation and the Department of Medical Epidemiology and Biostatistics at Karolinska.

The research revealed that the genetic component for developing ARFID was high—79% of the risk of developing the disease can be explained by genetic factors. “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 Dinkler.

The twins study is only the first step in better understanding the nature of ARFID and its genetic basis. Dinkler’s next phase of research will be to determine if ARFID is associated with other psychiatric disorders including anxiety and depression, neurodevelopmental disorders, and gastrointestinal problems. This work will also be carried out via twin studies, Dinkler said.

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