Eating Disorders - Clinical Case Series #7
Adapted/Edited by Dr Gurjot Brar from "Evolution and Psychiatry: Clinical Cases" by Prof. Henry O'Connell
Welcome to the seventh in our clinical case series, exploring common mental disorders through the lens of evolutionary psychiatry. A ‘problem-based learning’ (PBL) approach is taken with learning outcomes defined at the outset, followed by several clinical encounters with fictional scenarios, interspersed with theory responding to the learning objectives. This method has emerged globally in medical curricula and has a good evidence base in medical education promoting self-directed learning. We hope you enjoy this format and look forward to your feedback.
This case series will often refer to key principles defined in the following article published in July 2023 which serves as a primer:
Evolution – basic principles & applications to health and illness
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Eating Disorders
Learning Objectives
Outline briefly the key facts about eating disorders relating to clinical features and diagnostic criteria, epidemiology, aetiology, pathophysiology and management.
List the main evolutionary theories relating to eating disorders.
Outline the main evolutionary theories for eating disorders in males.
Outline how the evolutionary perspective can help inform treatment and prevention strategies for eating disorders.
‘Whatever has been going on for her, I think she’s developed an eating disorder.’
Denise Smith was always top of her class in both primary school and secondary school. She excelled in all of her subjects and she was also the captain of the hockey team and Year Head. She was always meticulous in her schoolwork and only once failed to get an A grade in her examinations. She reveled in getting good results and positive feedback from her teachers and parents. From the age of just twelve she was determined to get top grades in her examinations every year and go on to study Medicine. While she was never entirely happy with her weight or body shape, she also enjoyed receiving occasional compliments about her slim physique, although there were always parts of her body that she did not like.
Her schedule became busier in her penultimate year of secondary school, when she turned seventeen. Her hockey commitments increased with more competitions, as did her studies, with her final secondary school examination (the Leaving Certificate) fast approaching. Denise had always been a very healthy eater, in order to optimize her performance on the hockey field and to keep slim. As the various pressures mounted in her last two years of secondary school, she started to become gradually more restrictive in her eating practices and she started to lose weight. She also started to monitor her weight on a daily basis and decided that if she could get to a target weight of 40 kg that she would feel better about her body shape and perform better on the hockey field.
As the pressures mounted, she found that closely monitoring her food intake, weight and her body shape gave her a sense of control in a time when she felt she was starting to fall somewhat behind in her studies and underperforming on the hockey field. She also started to do extra exercise, running 5 kilometres every evening after hockey training. She did not at first realise the significance of her periods stopping. When her mother asked if they could have a talk, Denise politely agreed but minimised any problems, saying that she was under some pressure but doing well.
Problems came to a head when Denise collapsed on the field during a hockey training session. John Moloney was the team doctor. He had known Denise for five years and had been aware that she had been losing weight and struggling in recent months. He had tried to talk to her on a few occasions but she always kept him at a distance. He examined her after her collapse and drove her home. Her parents were shocked to see the doctor’s car pull up at their house. They got Denise to bed and then Dr Moloney asked to speak to them. ‘It looks like Denise may have been struggling for quite some time and I’m quite worried about her now. Whatever has been going on for her, I think she’s developed an eating disorder.’
Denise’s parents were shocked but relieved that they had some acknowledgement that Denise was unwell, thus acknowledging their own concerns. Dr Moloney then went on to outline some of the key clinical features of eating disorders.
Learning Objective 1:
Outline briefly the key facts about eating disorders relating to clinical features and diagnostic criteria, epidemiology, aetiology, pathophysiology and management.
The term eating disorders refers to both Anorexia Nervosa (AN) and Bulimia Nervosa (BN) although obesity has arguably become a more significant public health problem in many western countries in recent decades. For the purposes of this case, the emphasis is on AN and BN. Both conditions involve a morbid fear of fatness, distorted body image and abnormal associated behaviours including restriction of food intake, purging and excessive exercise. Amenorrhoea is frequently seen in AN, with abnormally low body weight. In contrast, weight is often normal in BN but a more prominent feature of this condition is binge eating and associated purging.
In practice, there is much overlap between the conditions and individuals may move between the diagnoses at different life stages. Traditionally, eating disorders have been far commoner in women than in men (ratios of e.g., 10:1) although relatively more men now experience eating disorders than before. The skewed sex ratio is even more evident in severe cases of AN that require life-saving, tube feeding in hospital where over 98% are female (Fuller et al, 2023). Aetiology may include genetic factors, personality type and adverse childhood experiences and eating disorders are found primarily in the western world although prevalence rates are increasing in the developing world, possibly related to increasing affluence and urbanization.
Management strategies are tailored to the particular pattern of problems and may include an initial emphasis on weight restoration through inpatient care and supervised feeding, psychotropic medication (generally high dose serotonergic antidepressant medications) and both individual and group psychotherapy.
Eating disorders are associated with significant psychiatric and physical morbidity and AN is generally regarded as the most lethal of psychiatric conditions with a 10% lifetime mortality, related to adverse physical health outcomes and a substantially elevated suicide risk.
A New Start
It is now six months since Denise’s collapse on the hockey field. In the days after that she reluctantly agreed to admission to ‘New Start’, a specialist eating disorders inpatient unit in Dublin. The prospect of gradually returning to normal eating patterns and reducing her exercise levels was at first terrifying for her. However, she trusted her treating team and accepted that she had developed Anorexia Nervosa. She decided to defer her final academic year of school and to return when she was feeling better. This helped greatly in reducing her stress levels and she was supported in the decision by her parents. She also took some comfort from handing over control of her diet and exercise levels to her treating team in New Start and she developed good relationships with a number of other young women admitted for treatment.
Her weight slowly and steadily increased over the subsequent weeks, her mood improved, as did her general attitude to her body image. She was prescribed Fluoxetine and found that this also helped with her mood and anxiety symptoms. Always the diligent student, Denise read widely about eating disorders and took a leading role in her group therapy sessions.
Towards the end of her admission at New Start, Denise started to do even more in depth research and reading on eating disorders. Beyond the clinical criteria and evidence based treatment approaches, she was now starting to discover potential reasons for why eating disorders are so prevalent, especially among women in western urbanized societies. She was particularly interested in the evolutionary aspects of eating disorders and, for her final group therapy session at New Start, she decided to do a brief presentation on her findings.
Dr Maureen Browne was the group facilitator and she and the group members welcomed her warmly: ‘Denise I am so happy to see how well you’ve done. And I am really looking forward to hearing about your reading and your views. And of course I know you’re now back on track to get the grades for medical school so all this reading and research will come in handy there!’
Denise started somewhat nervously but her confidence grew as she talked to the group of twenty teenagers (mostly female) in the room: ‘I developed Anorexia Nervosa over a number of years but, thanks to the great care and support of New Start and my family, I am now recovering and starting to get ready to get home and back to school. For some of you here, you are starting out on a long and difficult journey and my heart goes out to you. But please take some hope from my story. And please try and remember that there are lots of potential reasons why everyone could at some stage develop an eating disorder. I’ve been looking at reasons why we as a species, especially younger people such as ourselves, are so at risk. Hopefully my research will help you make sense of what’s going on for you’.
Learning Objective 2:
List the main evolutionary theories relating to eating disorders.
There are a number of theories relating to eating disorders, particularly AN, which have been reviewed by Abed & Ayton (2022). The main theories are summarised below
1. Reproductive Suppression Hypothesis
This, relatively older, theory proposes that eating restriction arises in response to disadvantageous environmental conditions, thus leading to reduced body fat to a level that is incompatible with ovulation (Wasser and Barash, 1983). This supposedly allows for the ability of females to alter the timing of their reproduction and anorexia develops as a result of mismatch. The main cues that signal disadvantageous reproductive conditions are intense female competition and unwanted sexual attention from males.
2. ‘Fleeing famine’ hypothesis
Here it is proposed that features of AN such as food restriction, denial of starvation and hyperactivity arose in response to famine in our past as a species, thus facilitating movement from areas of depletion (Guisinger, 2003). However, this theory has been challenged as it was likely dangerous to maintain prolonged food restriction in the ancestral environment and does not explain why those with anorexia resist eating food when it is readily available (Del Guidice, 2018).
3. The Sexual Competition Hypothesis (SCH)
The first two theories outlined relate mainly to AN but the SCH has the advantage of potentially applying to both AN and BN. The SCH is based on the proposition that female intra-sexual competition leads to a ‘drive for thinness’ (as a visual indicator of nubility and reproductive potential) and when this becomes extreme and dysfunctional, the result is either AN or BN. The novel environment of western urbanized environments with large numbers of autonomous females of reproductive age is thus seen as a driver of ‘the pursuit of thinness’ which, when goes into ‘overdrive’, manifests as AN. Additional factors include female autonomy in mating choices (in contrast to that seen in ancestral and traditional societies), reduced fertility and the ubiquity of images of nubile and attractive young females who may be mistaken for competitors (Abed, 1998; Abed et al., 2012; Nettersheim et al., 2018).
4. Extended Mismatch Hypotheses
Reflecting on intense female intrasexual competition being a driving factor in the development of eating disorders, Ayton and Ibrahim have further developed the theory to propose that intrasexual competition driven by modern social conditions (see SCH above) is complicated by the additional mismatch of the modern diet, primarily ultra-processed foods. Rantala et al (2019) have independently proposed a multifaceted mismatch theory which includes the effects of stress, stress hormones, immune responses, proinflammatory cytokines and many other co-morbid processes. Being in conflict between food consumption and mating has led to what the authors have termed the ‘adaptive metaproblem’ (Al-Shawaf, 2016). The advantage of this theory is that it incorporates not only anorexia and bulimia nervosa, but obesity and other related eating disorders (Abed & Ayton, 2022).
Life History Theory (LHT) may also have relevance to the study of eating disorders, with BN a manifestation of fast life history theory and AN being more related to slow life history strategies (Abed et al, 2012; Nettersheim et al, 2018).
“…I’m obviously not a female and not subject to the same evolutionary pressures?”
Paul was also one of the teenagers present in the room where Denise gave her talk. He is a 19 year old homosexual male who has been struggling with an eating disorder also. He often wishes to be thinner than he is and goes through cycles of bingeing and purging. On two occasions he has resorted to taking laxatives in an effort to reduce his weight. Paul was overweight as a young child and was often teased by his classmates at school. He was otherwise a quiet and obedient child, but somewhat of a perfectionist. He did well at his leaving cert going on to do political science at Trinity College Dublin. He was living out during his first year in dormitories and had just gone through a break-up when his issues with eating resurfaced. He began to control his caloric intake and began to exercise more, dropping weight rapidly. He began to purge daily and began to feel faint on occasion. One day during lectures, he fainted and was rushed into hospital. His potassium levels were dangerously low and he was in metabolic acidosis. After spending a few days in hospital he was transferred to ‘New Start’ where he has been for almost two weeks, making steady progress.
Afterwards, he waits to speak to Denise as he has become interested in the evolutionary basis for their shared problems with eating. “Denise, thank you so much for giving that talk, I felt it was very brave and inspiring. I wonder however, how those theories may relate to me as I’m obviously not a female and not subject to the same evolutionary pressures?” Denise stops to consider for a moment and realises she remembered reading about one of the theories accounting for eating disorders in males. “Paul I think there is one theory that does include males, I’ll send you on what I have and I hope it helps!”.
Learning Objective 3:
Outline the main evolutionary theories for eating disorders in males.
Eating disorders in males are a relatively new phenomenon and challenge the traditional evolutionary theories relating to eating disorders based on reproductive suppression and female competition. Unlike in females, eating disorders in males present as one of two variants. The female typical ‘drive for thinness’ variant is known to be more associated with homosexuality (Abed, 1998; Calzo et al., 2018; Li et al., 2010) whereas the other variant of body dissatisfaction, is the male-typical ‘drive for muscularity’ which focuses on upper-body musculature (Karazsia et al., 2017; Pope et al., 2000).
The Sexual Competition Hypothesis (SCH) (Abed, 1998), noted above, offers a plausible explanation for both variants. In the case for the ‘drive for thinness,’ the focus is to attract men relying on visual cues of attractiveness (Abed, 1998). Intrasexual competition can account for men displaying the other variant where the pursuit for larger upper body musculature is a direct competitive signal to rival men as well as an attractor for females (Lassek & Gaulin, 2009). Also, men’s fighting prowess, over evolutionary timescales, has been largely determined by upper body strength.
New perspectives for New Start
Dr Maureen Browne is very impressed by Denise’s progress and very hopeful for her future prognosis. Denise has had intensive intervention at an early age with an excellent clinical response and she is clearly highly motivated and insightful.
Dr Browne is also very interested in the presentation that Denise gave to the group and she goes on to do further reading of her own on evolutionary aspects of eating disorders, an area that was relatively unfamiliar to her until now.
As she sees it, the evolutionary perspective has potential for use in both individual and group psychotherapy.
Learning Objective 4:
Outline how the evolutionary perspective can help inform treatment and prevention strategies for eating disorders.
Dr Browne’s research into the evolutionary theories on eating disorders leads her to reflect on how this can help inform treatment or even prevention for eating disorders. She considers how many of the theories rest on the concept of evolutionary mismatch and ponders how it may be reduced in this patient group. Since Denise’s presentation, Dr Browne feels like her eyes have suddenly been opened to the ubiquity of images of young, slim, attractive females in advertising and other media. For her next group psychotherapy session, she decides that she will ask the group to review a sample of magazines for such images and write letters to the editors outlining the potential harm that such images may cause.
The evolutionary perspective may be used to help destigmatize eating disorders for individual sufferers and their families, by highlighting that they represent a pathological and dysfunctional exaggeration of adaptive responses that arise as a result of mismatch with modern, westernized environmental conditions. This offers patients and families a powerful unifying explanation as to why that particular person is particularly vulnerable to eating disorders, rather than laying the blame entirely on proximate mechanistic pathways.
Reframing the targets of therapy to improving patient functional capacities may have more success, rather than for example a particular BMI which if you do not cross the threshold for, means in some cases you do not have access to a particular service. (Mishra & Harrop, 2023; Toppino et al., 2022). Successful therapy in this case would restore normative functioning of evolved behavioural systems (Troisi, 2022).
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