Twitching eye movement could offer objective anorexia diagnosis
A new study is describing a potential biomarker to identify a person’s risk of developing anorexia nervosa. The research proposes measuring levels of anxiety alongside a specific type of twitching eye movement can effectively identify both those with, and at risk of developing, the eating disorder.
Like most mental illness anorexia nervosa is diagnosed by a doctor who assesses a variety of symptoms before making a judgement call. So far, there is no blood test or objective measure that can be used to identify those with the condition, or those at risk of developing the condition.
This new research, led by scientists from Australia's Swinburne Anorexia Nervosa Research Group, followed on from prior studies proposing a particular kind of atypical eye movement, known as square wave jerks, could distinguish anorexia nervosa patients from others.
Square wave jerks are tiny saccadic eye movements. They are involuntary and can be detected by looking for brief flickering moments where a person’s eyes move away from a target they are focusing on.
To investigate the veracity of this potential biomarker, the researchers recruited 80 women – 20 currently experiencing anorexia nervosa, 20 recovered anorexia nervosa patients at a normal weight, 20 healthy sisters of women with anorexia nervosa, and 20 healthy controls.
When rates of square wave jerks were combined with an anxiety measure, known as the State Trait Anxiety Inventory, the researchers were able to distinguish anorexia nervosa patients from healthy controls with 92.5 percent accuracy.
Interestingly, square wave jerk rates did not differ significantly between anorexia nervosa patients, recovered anorexia nervosa patients and healthy sisters of anorexia nervosa patients. This compellingly indicates the condition shares a potential genetic link, regardless of the acute disease activity.
"Eye movements use very specific brain regions, so when we see these types of atypical eye movements, we have a pretty good idea about which brain areas are not working the way they should," says Andrea Phillipou, lead researcher on the project. "These areas are also involved in other functions related to anorexia nervosa — such as body image — so it gives us an idea of which brain areas we could target with treatments such as non-invasive brain stimulation."
Previous research has indicated anorexia nervosa is a highly heritable condition. The finding that healthy sisters of anorexia nervosa patients share this prospective biomarker affirms this potential genetic predisposition to the condition.
Phillipou says further work will hopefully validate this biomarker as a useful screening tool to help detect those most at risk of developing anorexia nervosa. This would help doctors implement preventative measures at the earliest opportunity.
"With more research, we're hoping that we'll be able to use this biomarker as a screening tool to identify people who may be at risk of developing anorexia nervosa," says Phillipou. "If we're able to do this, we'll be able to implement things to help prevent people developing the condition in the first place."
The new research was published in the Australian and New Zealand Journal of Psychiatry.