Theme: Health issues and Disease
Disclaimer: Here at Under the Microscope we aim to educate our readers and raise awareness about issues in healthcare that we believe are pertinent to society. Whilst this article does take a scientific approach, it discusses themes that may be sensitive for some of our readers. If matters on eating disorders are triggering to you, please feel free to skip this article.
Anorexia Nervosa is an eating disorder characterised by an unhealthily low body weight, often sustained by restrictive eating and excessive exercise, which stems from an intense fear of weight gain. Over the last few years, there has been much debate over the true etiology of this condition, and whether psychological or neurological factors play a more significant role. Scientists have questioned whether obsessive dieting leads to neurobiological changes which fuel these obsessive behaviours, or whether someone’s inherent neurological function makes them more vulnerable from the start. Whilst the real answer is unclear, researchers have been able to conclude that the answer is a messy mixture of the two.
Interestingly, there is a lot of evidence to suggest that childhood temperament and intrinsic personality traits influence how likely someone is to develop an eating disorder during adolescence.  Some of these traits are characterised as inhibition, negative emotionality, drive for thinness and perfectionism, which will be explained in more depth in the bibliography below. It is believed that children who display these traits are more vulnerable to developing anorexia as a teenager when hormonal changes occur during puberty, and they begin to experience stress from cultural factors and societal pressures. Combine these factors, and an individual may begin to diet obsessively, heavily monitoring calorie intake and exercising multiple times a day, which instinctively would lead to weight loss. As a consequence, one may experience starvation-induced metabolic and neurochemical changes which sustain AN behaviours, thus pulling them into the AN downward spiral. For example, when someone is malnourished, the brain begins to produce higher concentrations of a chemical called corticotropin-releasing-hormone or CRH. When this hormone was administered in rats, they began to demonstrate behavioural changes which are associated with AN, such as decreased sexual activity, altered emotionality, and a diminished appetite. Furthermore, these neurochemical changes that occur during starvation also intensify emotional dysfunctions that may lead to the development of Depression or Obsessive Compulsive Disorder, which fuel the vicious cycle of excessive dieting and exercise. This cycle is illustrated in the diagram below. 
Alongside all of this, researchers have begun to explore how neural circuits play a role in the development of eating disorders, leading them to question whether certain neurotransmitters may be responsible for increasing the risk of developing anorexia. One example of this is serotonin, which you may have heard being referred to as the ‘happy chemical’. In reality, serotonin is responsible for a wide variety of sensations, and studies have shown that excess amounts of this neurotransmitter can actually contribute to feelings of irritability and anxiety. According to a study, people who are more vulnerable to eating disorders have higher levels of serotonin in the brain and an imbalance in receptor activity, which leads for them to experience emotions that amplify restrictive eating habits. This may explain why even after recovery, individuals with a history of anorexia demonstrate much higher levels of serotonin in the brain than the average healthy human. However, when individuals begin dieting and restricting their intake of food, serotonin levels begin to drop drastically, because this chemical is synthesised from the macromolecules we consume from food. As these individuals had an excess amount initially, the drop in serotonin concentration actually decreases stress and agitation, which associates starvation with improved mood. As serotonin levels continue to drop, our brains adapt by creating more serotonin receptors, so there is more opportunity for serotonin to bind to a receptor and transmit information. As a consequence, this sends the brain into a serotonin overdrive, spiking levels of anxiety once more, so individuals are inclined to restrict their diet further. This makes it very difficult for individuals to overcome their eating disorder without support from a mental health specialist - as food is no longer perceived as a reward but programmed to induce stress and anxiety. 
Whilst the science above is a significant simplification of reality, I hope it does outline just how complex an eating disorder can be. Given the stigma and prejudice that exists surrounding conditions like anorexia, it is important to challenge our biases and strive to be more empathetic to others’ experiences. You’d be surprised to know that a lot of the misconceptions we have about eating disorders, turn out to be quite far from the truth: for example, most people would assume that those suffering from eating disorders can be identifiable by a thin physique when in reality only 6% of ED patients are underweight.
As outlined above, eating disorders can be influenced by a variety of factors including social pressures, personality traits and one’s inherent neurobiology. Whilst there are many steps we can take to look after our mental health and minimise the risks of developing mental health conditions, a lot of the time there are genetic factors working behind the scenes, that make part of the process out of our control. So the next time you hear someone say eating disorders are just another ‘cry for attention’, I urge you to challenge their biases, because no two of us are built in the exact same way.
Kaye, W., Fudge, J. and Paulus, M., 2009. New insights into symptoms and neurocircuit function of anorexia nervosa. Nature Reviews Neuroscience, 10(8), pp.573-584.
Ely, A., Berner, L., Wierenga, C. and Kaye, W., 2016. Neurobiology Of Eating Disorders: Clinical Implications. [online] Psychiatric Times. Available at: < https://www.psychiatrictimes.com/view/neurobiology-eating-disorders-clinical-implications > [Accessed 21 September 2020].
National Association of Anorexia Nervosa and Associated Disorders. 2020. Eating Disorder Statistics • National Association Of Anorexia Nervosa And Associated Disorders. [online] Available at: < https://anad.org/education-and-awareness/about-eating-disorders/eating-disorders-statistics/ > [Accessed 21 September 2020].
Etiology: the cause of a medical condition
Inhibition: the ability to control one’s desires and restrict themselves from acting upon impulses
Perfectionism: the need or desire to be perceived as perfect according to a particular standard
Drive for thinness: the desire to achieve a ‘thin’ physique
Negative emotionality: the tendency for someone to experience negative feelings associated with mental health conditions ie someone easily stressed or agitated
Corticotropin releasing hormone: a hormone involved in stress response that stimulates the release of another hormone
Neurotransmitters: a kind of chemical produced by the brain that acts as a ‘messenger’ by passing on pieces of information from one part of the brain to another.
Receptor: the site at which neurotransmitters bind and ‘pass on’ the information/message