By Katie Lau
Eating disorders cause painful emotional, physical, and mental stress and harm to those who suffer from them, involving disturbed perception of body image, weight, and food (Treasure et al., 2020). Perhaps this COVID-19 pandemic has even worsened the symptoms of such patients or brought about higher rates of eating disorders than before; triggers range from lots of time alone and an increased use of social media, a lack of social interaction and professional support, or boredom which can lead to overeating. This article focuses on the neural mechanisms and susceptibility behind such psychiatric disorders, including anorexia nervosa, bulimia nervosa, binge-eating disorder, avoidant-restrictive food intake disorder, and pica and rumination disorder, and the challenges faced by these patients in a COVID-19 world.
Anorexia nervosa (AN) patients severely restrict their food intake and/or undertake other behaviours with the motivation of weight loss – this can include overexercising, self-induced vomiting, and the overuse of laxatives. Concerns about weight and shape make AN different from avoidant-restrictive food intake disorder (ARFID). ARFID patients are not concerned about weight and body shape but suffer weight loss due to lacking interest in food/eating or avoiding it. This can be due to the fear of vomiting or choking, based on past traumatic experiences. Bulimia nervosa (BN) is characterised by episodes of binge-eating (eating excessively without control), followed by certain behaviours to compensate. Most notably, this includes self-induced vomiting, alongside excessive exercise, misuse of medicines, and fasting. These symptoms are also triggered by a negative perception of physical appearance and fear of weight gain. Binge eating disorder (BED) also involves distressing episodes of excessive eating, but with less compensatory behaviours than those of BN patients. Those with pica disorder tend to eat non-food substances – such as dirt, clay, ice, glue and flaking paint. This is commonly out of boredom, curiosity, or for taste. Rumination disorder (RD) is characterised by regurgitating food after swallowing it – without having felt disgust or nausea or having vomited involuntarily (Treasure et al., 2020).
Microbiota and reward learning
The human microbiota is comprised of 100 trillion microbes, mainly of which are bacteria. Collectively their genomes form the microbiome. Neural connections between the gut and brain are not unheard of – the microbiota may therefore potentially impact eating disorders. Studies have found that patients suffering from AN have altered microbial composition compared to controls, and such composition and diversity could be correlated with BMI and blood insulin levels (Frank et al., 2019). Descriptive studies have found AN patients possess lower faecal microbial diversity than average. Anomalies in attention and impulsiveness are present in BN patients – this may underpin its association with attention deficit hyperactivity disorder (ADHD). Furthermore, anomalies in reward learning may lead to the maintenance of eating disorder behaviours. AN patients have delayed responses to rewards, the opposite of BED patient responses. AN patients also show avoidance to food cues, while those with BED demonstrate increased attention to them. The behavioural susceptibility theory proposes there is a genetic predisposal to such contrasting relationships with food; these observed behaviours serve as evidence to support this (Treasure et al., 2020). Investigations into whether those with eating disorders found food as rewarding/pleasurable as healthy controls revealed that those with AN take less pleasure in food, especially high-calorie foods, potentially leading to less of its intake. BN individuals have self-reported high levels of pleasure and sensation-seeking behaviour. Their self-reported desire to eat for pleasure when not losing weight has been predicted to trigger out-of-control eating; there is also an association between this desire and the frequency of binge eating episodes. However, compared to healthy controls, both AN and BN individuals consume large amounts of artificial sweetener, through gum, diet drinks and sweetener packets. These observations have led to the use of behavioural and neuroimaging studies to further investigate these reward systems (Steinglass et al., 2019).
COVID-19 and implications for eating disorders
The effect of COVID-19 on those with eating disorders has not been fully established, but such individuals are at high risk of harm, physically – the fraility of AN patients, electrolyte disturbance in BN patients, and cardiovascular risk possessed by those with BED, and mentally – the stress of confinement at home and inability to access normal treatment. The severity of symptoms is speculated to increase, due to less accessibility to treatment according to evidence-based guidelines – as well as the burden on carers. Worries surrounding health and fitness during isolation can trigger development of eating disorders in those who are vulnerable. Other risk factors also include longer periods of time spent on social media as a result of confinement, inducing further exposure to the idealisation of specific body sizes. Isolation may also worsen loneliness, one of the consequences of AN. Struggles with emotional regulation in confinement may lead to greater occurrences of binge eating or purging. The pandemic reveals the importance of connection and pain of loneliness – an often-forgotten symptom of those with existing mental health problems. Furthermore, patients with eating disorders often lack insight into their illness and struggle with communication – as a result, they may be unwilling to seek help (Fernández‐Aranda et al., 2020).
References:
Fernández‐Aranda, F., Casas, M., Claes, L., Bryan, D. C., Favaro, A., Granero, R., Gudiol, C., Jiménez‐Murcia, S., Karwautz, A., Le Grange, D., Menchón, J. M., Tchanturia, K. & Treasure, J. (2020) COVID‐19 and implications for eating disorders. European Eating Disorders Review. 28 (3), 239-245. Available from: https://onlinelibrary.wiley.com/doi/abs/10.1002/erv.2738. Available from: doi: 10.1002/erv.2738.
Frank, G. K. W., Shott, M. E. & DeGuzman, M. C. (2019) The Neurobiology of Eating Disorders. Child and Adolescent Psychiatric Clinics of North America. 28 (4), 629-640. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6709695/. Available from: doi: 10.1016/j.chc.2019.05.007.
Steinglass, J. E., Berner, L. A. & Attia, E. (2019) Cognitive Neuroscience of Eating Disorders. The Psychiatric Clinics of North America. 42 (1), 75-91. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6601331/. Available from: doi: 10.1016/j.psc.2018.10.008.
Treasure, J., Duarte, T. A. & Schmidt, U. (2020) Eating disorders. The Lancet (British Edition). 395 (10227), 899-911. Available from: http://dx.doi.org/10.1016/S0140-6736(20)30059-3. Available from: doi: 10.1016/S0140-6736(20)30059-3.
Imperial Bioscience Review 