A global study involving Kiwi researchers has found the origins of anorexia may lie in some people's genes and the disorder is not simply a psychological illness.
The findings were released on Tuesday, showing that some people are born with a biological predisposition to developing anorexia nervosa "that affects the function of the brain as well as the metabolic system".
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According to EDANZ, people suffering from anorexia reduce their food intake, which causes dramatic weight loss.
The DNA of almost 17,000 patients was sampled by the Anorexia Nervosa Genetics Initiative (ANGI). The lead researcher was Professor Cynthia Bulik from the University of North Carolina and Sweden's Karolinska Institute, who worked with more than 100 scientists, including researchers from New Zealand - Dr Jenny Jordan and Professor Martin Kennedy.
This data was then compared with more than 55,000 control cases (people without anorexia) and found that there were eight genetic variants associated with anorexia.
It was also found that the genetic basis of anorexia "overlaps with traits associated with people's ability to metabolise fats and sugars, and body mass index" as well as other disorders like obsessive-compulsive disorder, depression and anxiety. Genetic factors associated with anorexia also influence physical activity.
The scientists concluded this showed the origins of the disorder were not only psychological but metabolic and say the new study will help clinicians looking for better ways of treating the disease, which has the highest mortality rate of any psychiatric disorder.
Dr Jordan said currently most treatments are psychological therapies that help patients with regaining weight and re-establishing normal eating, without any specific medication.
She said this would help provide a different way of looking at the disease.
"Many people diet but only a few develop anorexia nervosa with very low levels of weight and sometimes extreme levels of exercise," Dr Jordan said in a statement.
"The findings that there are genetic differences relating to metabolism in people with anorexia in our study helps make sense of that. It may also help explain in part why recovery is such a struggle. These findings, that it is not just a psychiatric condition, will be hugely validating for many with anorexia nervosa and their families."
A Christchurch woman who had anorexia and participated in the study, Samantha, whose last name Newshub has agreed not to publish online, said it was emotional reading the results.
"So much of mental illness and anorexia, you can't actually see it, it's all in your head. So I was hoping to get some sort of answer for what we are going through," she told Newshub.
"I was actually quite emotional reading the results and realising there is actually some reason why people suffer from anorexia."
Prof Kennedy said while those with the identified genetic predispositions are more likely to develop anorexia, not everyone with those patterns of DNA will do so.
"Nobody chooses to succumb to this awful disease, and we need these kinds of new insights to help people survive and move on with their lives."
Participants came from 17 countries across North America, Europe and Australasia. The findings were published in the journal Nature Genetics.