Can the brain’s reward circuits fight anorexia?
Mental Health Anorexia Nervosa Eating Disorders

Can the brain’s reward circuits fight anorexia?

Dr. Clare Foldi
Dr. Clare Foldi

In 10 seconds? Although researchers are still hunting for a cure, scientists are discovering how one of the most lethal psychiatric conditions, anorexia nervosa, develops. It seems that targeting the brain’s reward pathways can kick off the survival instinct.

What’s the story? Anorexia is just the term for the inability to eat whereas anorexia nervosa (AN) is a dangerous psychological disorder pushing sufferers to lose weight by starving themselves... sometimes to death. In the US approximately 0.5-1% of younger women between 13-20 years suffer from AN. An estimated 1 in 5 patients develop a long-term, severe illness and the same proportion dies from the condition – which, along with other eating disorders cost the US over $65 to treat annually.

So, it happens in the brain? There is no clear answer yet and scientists are still trying to understand what makes AN set in. But a recent paper has found that it definitely happens “to the brain” – it affects it so much that it reduces volumes, practically shrinking the brain. And this reduction is more prominent – 2-4 times bigger – than in other psychological disorders, such as ADHD and depression. The researchers did not address it but they came up with a hypothesis that the reduction of the body mass index (BMI) may be a cause behind this shrinkage. On a positive note, they observed that this process can be reversed.

Do we know what causes AN? Unfortunately, we don’t. There seem to be some risk factors, though. Research showed that childhood immune diseases boost the risk of its development by 36%. However, hopes were raised a few years ago when researchers found that tweaking the brain’s reward system can turn on the drive to eat.

But why don’t patients with anorexia nervosa crave food? Part of the answer lies in how the brain circuitry controlling energy levels interacts with the sense of reward that comes with eating. AN sufferers don’t feel this “reward” and their nervous system suppresses their urge to survive, which can explain the lack of hunger.

Schematic representation of the hypothetical chronic stimulation of orexigenic neuropeptides on the reward circuitry in anorexia nervosa. Source: Gorwood, Blanchet-Collet, Epelbaum et al, 2016.
Schematic representation of the hypothetical chronic stimulation of orexigenic neuropeptides on the reward circuitry in anorexia nervosa. Source: Gorwood, Blanchet-Collet, Epelbaum et al, 2016.

How come we have such a vague understanding of it? Ethical concerns limit the use of live human subjects to study the brain circuits where AN is formed. (Scientists note that research in humans would need to involve a large number of people, including children – an obvious ethical barrier). As an alternative, scientists are studying the brain’s reward system underpinning anorexia using an activity-based anorexia model in rodents.

You mentioned hope… anything promising came out of these studies? We have to be careful and let me explain why. We know that the release of dopamine, a neurotransmitter in the brain, is responsible for the sense of pleasure. Addictive drugs, for example, hijack this function. Anorexia nervosa sufferers, on the other hand, become unable to derive pleasure from eating. Researchers are now able to selectively switch neural circuits on or off and activate the pathway that boosts the feeling of reward. This suppresses anorexia and prevents extreme weight loss in rodents.

Will this lead to a cure for humans? Hopefully but, again, because of the above-mentioned ethical concerns we need to find some other ways to find a human cure. Currently, there is no effective treatment for this life-threatening condition – there is no FDA-approved drug, for example. Societal pressure about body image, a lack of understanding from large sections of the public and the proliferation of online communities encouraging starvation and extreme weight loss poses an additional danger.

So, how is anorexia nervosa treated?

It's a notoriously difficult and complex task involving doctors, mental health professionals and dietitians. New approaches focus on the positive involvement of families to help teenage sufferers.

Previously professionals blamed controlling parents for the development of anorexia, but lately, they have been empowering them to help with the treatment of their children, by helping them to understand the impact of brain circuit dysfunction. For example, a study and a follow-up study in the UK have found that this approach cut hospital readmissions and saved the UK’s health service, the NHS around £10,000-14,500 per patient per year.

Anorexia nervosa is treated by talking therapies and a recent randomized controlled trial found that a method, called MANTRA lead to an average weight gain of 6kg over 2 years and tended to be more trusted by patients than other interventions.

If you are in the US and need support, contact the National Eating Disorders Association (NEDA) helpline

Dr. Clare Foldi has distilled 9 research papers, saving you 31,5 hours of reading time

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