Anorexia nervosa is an eating disorder characterised by restriction of energy intake resulting in low body weight and an intense fear of weight gain.
Though anorexia nervosa may occur at any age, the risk is highest in young people between the ages of 13-18 years old.
Management is typically with talking therapies and supervised weight gain. However those at-risk of significant complications may require urgent admission and inpatient management.
It follows a variable course, but less than half of patients fully recover and mortality is 5 times that of the general population.
It is estimated that the lifetime prevalence of anorexia nervosa is 2-4% in women.
Though more common in women, men are affected. Incidence rates are estimated at 4.2-12.6 per 100,000 person-years in women and 1 per 100,000 person-years in men.
Transgender adolescents are at risk of eating disorders including anorexia nervosa though accurate epidemiological data is not available, it is suspected to be higher than cisgender adolescents.
Epidemiological studies often show significant variation in the estimates of prevalence and incidence. This may be in part due to changes in diagnostic criteria and cases going unrecognised.
Though little is understood about the aetiology of anorexia nervosa, a number of risk factors have been identified.
The pathogenesis of anorexia nervosa is unknown.
Little is currently understood about the development of the condition. Genome-wide association studies (GWAS) have implicated a number of gene loci that may influence its development. Twin studies have shown inconclusive results.
Neuroimaging has shown changes in the function and structure of the brains of patients with anorexia nervosa. However, it is unknown if these are causative or result from the disease. More recently there has been interest in the role of the immune system and intestinal microbiota.
Anorexia nervosa manifestations include low body weight and fear of weight gain as well as the results of low body weight and malnutrition.
A significant amount of variation may be seen in the clinical features of anorexia nervosa. Patients may experience low libido and a loss of interest in personal relationships. In women menstrual dysfunction - predominately amenorrhoea may be seen. In those who have not undergone puberty, pubertal delay can occur. It is commonly associated with other mental health illnesses. A history of deliberate self-harm is common.
The recognition and diagnosis of anorexia requires an attentive and thorough history and examination.
Those suspected of suffering from an eating disorder should be referred from primary care to the local specialty team for further assessment. Parents and carers, particularly in younger patients, may have valuable insights.
The SCOFF questionnaire is a short and simple tool that can be used in primary care to help identify patients that may be suffering with an eating disorder.
It should not be used alone but as part of a wider assessment of a patient at risk for an eating disorder.
Two or more positive responses is considered indicative of anorexia nervosa or bulimia nervosa.
DSM-V was released in 2013 and provides diagnostic criteria to help formalise the diagnosis of anorexia nervosa. Though formal criteria can be helpful it does not replace a holistic review of an individual patients symptoms and the impact on their life and health.
The following are noted as criteria for a diagnosis of anorexia nervosa:
Each patient with suspected anorexia nervosa requires review with age-appropriate specialist teams.
Detailed information on the assessment of both adults and those under the age of 18 have been published by the Royal College of Psychiatrists:
The focus of these guidelines is the assessment and management of patients with severe disease. In this chapter, we will discuss aspects of the assessment of patients with anorexia, for more detail on this and risk stratification see the links above.
Most patients will be managed in the community with input from relevant age-appropriate services. Patients who have been diagnosed late, with severe features or have failed community management may need inpatient care at a specialist eating disorders unit or if medical input is required, a hospital.
Every patient requires a risk assessment for suicide and self-harm. Any perceived risk should be urgently discussed with specialist care.
A comprehensive physical examination should be completed with the permission of the patient. Signs of muscle wasting will normally be evident. Evaluate the patient's hydration status, dehydration can be significant, and may warrant inpatient management.
The patients height, weight and BMI should be recorded. In those under the age of 18, the BMI should be plotted on a centile chart. Both the BMI and rate of weight loss can help identify those at the greatest risk of complications.
When possible, care is based in the community, with patients receiving talking therapies and supervised weight gain.
Most patients will be managed in the community. Talking therapy and supervised weight gain form the cornerstone of care. Patients who do not respond to outpatient management or present with high-risk features or those that cause immediate concern should be considered for inpatient care.
In those at risk of significant risk of complication or with severe disease (e.g. bradycardia, ECG changes, electrolyte abnormalities, very low BMI, rapid weight loss, dehydration, organ failure, suicide risk), admission to hospital is required. It may also be considered if patients fail to respond to community management.
Specialist eating disorders units are able to provide most care including (from MARSIPAN): 'nasogastric insertion and feeding, daily biochemical tests, frequent nursing observations, prevention of symptomatic behaviours (water drinking, absconding, exercising, etc.), daily ECG, sedation of a resisting patient, use and management of mental health legislation, treatment of pressure sores, immediate cardiac resuscitation without presence of ‘crash’ team'.
They are typically unable to provide 'intravenous fluids, artificial ventilation, cardiac monitoring, central venous pressure lines, total parenteral nutrition, cardiac resuscitation (‘crash’) team, treatment of serious medical complications'. These patients need admission to a hospital under the care of a medical team with ongoing psychiatric input.
The management of severely ill patients with anorexia nervosa is covered in detail in the MARSIPAN and Junior MARSIPAN guidelines. A full re-wording or that is beyond the scope of this note. Input for these patients needs to come from psychiatrists, medics and dieticians. Use of the Children Act 1989 or Section 3 of the Mental Health Act may be required, though this is used as a last resort.
Refeeding syndrome is a potentially fatal complication and is covered in some detail in the MARSIPAN & Junior MARSIPAN guidelines. It occurs in malnourished patients who then receive a sudden increase in their calorific intake resulting in electrolyte abnormalities and fluid retention. We cover the pathophysiology in our Refeeding Syndrome note.
The aim is to avoid refeeding syndrome and undernutrition. Some factors that increase the risk of refeeding syndrome are:
There is some debate around the optimal nutritional intake to advise initially which is reflected in the MARSIPAN guidance. However, in simple terms consideration must be given to the initial calorie intake and either inpatient or outpatient monitoring of electrolytes and ECG’s may be warranted.
NICE guidance 69 (updated 2020) advises considering CBT-ED, MANTRA or SSCM:
CBT-ED (individual Eating-Disorder-focused Cognitive Behavioural Therapy): this is a specialised form of CBT, consisting of 40 sessions over 40 weeks - with twice-weekly sessions initially. Together with a therapist, the patient forms a personalised plan to help them understand and cope with their feelings and disease.
MANTRA (Maudsley Anorexia Nervosa Treatment for Adults): consists of 20 sessions, weekly for the first ten weeks, then tailored to the patient. Guided by a therapist who helps the patient evaluate what is important to them and what causes their eating disorder. Aims to help patients develop a non-anorexic identity.
SSCM (Specialist Supportive Clinical Management): consists of 20 sessions, a therapist helps the patient understand the relationship between their feelings, eating behaviour and disorder. Looks to establish a weight goal and encourage healthy eating.
Where one technique has failed, another may be trialled. If ineffective or contraindicated, FPT (eating-disorder-focused focal psychodynamic therapy) can be offered. Consisting of 40 sessions over 40 weeks, it is split into three phases:
NICE guidelines 69 (updated 2020) advise anorexia-nervosa-focused family therapy (FT-AN) is considered first-line. It typically consists of 18-20 sessions over a 1-year period. Sessions separate from family or carers may also be facilitated. It is divided into three phases:
The alternatives are CBT-ED or adolescent-focused psychotherapy for those who do not want FT-AN or in those in whom it has been ineffective.
Anorexia nervosa follows a highly varied course.
It is thought that just under half (46%) of patients will recover whilst 20% will develop chronic disease. The remainder show partial improvement.
Anorexia nervosa has the highest mortality of any mental health illness. Mortality rates are estimated to be 5 times higher than the general population. Causes of death include cardiovascular complications, infections and suicide.
Figures from NICE CKS.
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