Deep brain stimulation holds promise as a treatment for anorexia nervosa, which has the highest mortality rate of any psychiatric disorder, a new Toronto-led study has found.

Researchers implanted electrodes deep in the brains of 16 women ages 21 to 57 who had battled anorexia for an average of 18 years and were dangerously underweight.

Those electrodes provided constant pulses of electricity to circuits of the brain linked with the eating disorder and with the emotions that are believed to drive it.

Over the course of a year, doctors studied the brain scans of the patients, finding changes in brain activity, and improved mental and physical health in the majority of the women.

Dr. Nir Lipsman, lead author of the study published in the U.K.-based journal The Lancet Psychiatry, said researchers chose only the most severe, treatment-resistant anorexia patients to include in the study. The patients had an average body mass index of 13.8.

The normal range is 18.5 to 24.9.

"There has to be a very longstanding, established history of what we call non-response. These are patients who have tried everything and nothing has worked and the average person in our study was sick upwards of 18 years, which was more than half of their life. These are really and truly the patients who have been sick the longest and are the most susceptible to the long-term effects of anorexia," Lipsman, a scientist and neurosurgeon at Sunnybrook Health Sciences Centre in Toronto told CTV News Channel.

He said anorexia is a complex, multi-symptom, multi-causal disease but research has shown that some of the symptoms that drive it and make it so difficult to treat are “actually emotion-related symptoms, things like depression, things like anxiety.” Deep brain stimulation is a tool to access the areas of the brain that trigger those emotions and hopefully, can help patients overcome the symptoms that block effective treatment.

About 0.5 per cent of people worldwide have anorexia, with teenage girls accounting for the majority of cases. The eating disorder is characterized by persistent concerns about bodyweight, shape and size, and many patients experience mood and anxiety disorders, deny the illness and avoid seeking medical help.

Chronic anorexia leads to malnutrition and a range of severe health problems such as weak bones and muscles, infertility, heart problems and seizures. The condition can be fatal.

The Toronto researchers caution that their study was small and had no control group.

There were also some complications. One patient developed an infection and needed to have the electrodes removed and then implanted again. During the course of the study, two patients asked to have the electrodes removed. Researchers believe that’s possibly because the women were uncomfortable with their weight gain.

For the remaining 14, mood and anxiety symptoms reduced in five patients and depression fell in 10 of them. The average BMI of the group increased to 17.3 and six patients achieved a normal BMI of 18.5 or more.

"Anorexia remains the psychiatric disorder with the highest mortality rate, and there is an urgent need to develop safe, effective, evidence-driven treatments that are informed by a growing understanding of brain circuitry," study author, Dr. Andres Lozano, a professor at the University of Toronto, said in a press release.

"While our results show some early promise, more research will be needed before this becomes available for patients with anorexia."

Commenting on the study, Dr. Carrie McAdams at the University of Texas said conventional treatments of behavioural modifications and psychological therapy to address self-esteem, eating and body dissatisfaction disorders result in nearly half of adult women relapsing within a year.

"This work shows how modern neuroscience can lead to a new treatment and simultaneously improve understanding of perpetuating factors in a complex, multifactorial disease."

Deep brain stimulation has also been shown to be highly effective in treating Parkinson’s disease, dystonia and tremors.