Eating disorders
There are two well-defined eating disorders, anorexia nervosa (AN) and
bulimia nervosa (BN); they share some overlapping features.
Ninety per cent of people affected are female.
There is a much higher prevalence of abnormal eating behaviour in the
population that does not meet diagnostic criteria for AN or BN but may
attract a diagnostic label such as ‘binge eating disorder’.
In developed societies, obesity is arguably a much greater problem but is
usually considered to be more a disorder of lifestyle or physiology than a
psychiatric disorder.
Anorexia nervosa
The lifetime risk of anorexia nervosa for women living in Europe is
approximately 1–2% (for men it is < 0.5%) with a peak age of onset of
15–19 years.
Predisposing factors include familiality (both genetic and shared
environmental factors appear to play a role) and ‘neurotic’ personality
traits.
Clinical features
There is marked weight loss, arising from food avoidance, often in
combination with bingeing, purging, excessive exercise and/ or the use of
diuretics and laxatives. Body image is profoundly disturbed so that,
despite emaciation, patients still feel overweight and are terrified of
weight gain.
These preoccupations are intense and pervasive, and the false beliefs may
be held with a conviction approaching the delusional.
Anxiety and depressive symptoms are common accompaniments. Downy
hair (lanugo) may develop on the back, forearms and cheeks. Extreme
starvation is associated with a wide range of physiological and
pathological bodily changes. All organ systems may be affected, although
the most serious problems are cardiac and skeletal.
Pathogenesis
The underlying cause is unclear but probably includes personality (high
neuroticism), genetic (twin studies indicate heritability of 0.3–0.5) and
environmental factors, including, in many societies, the social pressure on
women to be thin.
Diagnosis
Differential diagnosis is from other causes of weight loss, including
psychiatric disorders such as
depression,
inflammatory bowel disease
malabsorption
hypopituitarism
Cancer.
although it is important to remember that AN can coexist with any of
these. The diagnosis is based on a pronounced fear of fatness despite
being thin, and on the absence of an adequate alternative explanation for
weight loss.
Management
The aims of management are to ensure patients’ physical wellbeing while
helping them to gain weight by addressing the beliefs and behaviours that
maintain the low weight.
Treatment is usually given on an outpatient basis. Inpatient treatment
should be reserved for those at risk of death from medical complications
or from suicide. There is a limited evidence base for CBT-based
psychological treatments.
Family behavior therapy (FBT) has efficacy among adolescent but not
adult patients. Psychotropic drugs are of no proven benefit in AN but
antidepressant medication may be indicated in those with clear-cut
comorbid depressive disorder.
Weight gain is best achieved in a collaborative fashion.
Compulsory admission and refeeding (including tube feeding) are very
occasionally resorted to when patients are at risk of death and other
measures have failed. While this may produce a short-term improvement
in weight, it rarely changes long-term prognosis.
Prognosis
Two-thirds of patients with AN no longer meet diagnostic criteria at 5-
year follow-up. However, long-term follow-up studies suggest that many
sufferers continue to have a relatively low body mass index (BMI),
suggesting that the symptoms do not completely resolve. Approximately
20% of patients develop a chronic, intractable disorder. Long-term
follow-up studies demonstrate that minimum lifetime BMI is the
strongest prognostic indicator (BMI < 11.5 is associated with an
standardised mortality ratio of 4–5). Other indicators of poor prognosis
are comorbid BN and atypical demographics (very early or relatively late
onset, male gender). Forty per cent of additional deaths are due to suicide,
the remainder being due to complications of starvation.
Bulimia nervosa
The prevalence of BN is difficult to determine with precision, as only a
small proportion of sufferers come to medical attention. It is believed to
be more common than AN, with a similar gender ratio. Peak age of onset
is slightly later than for AN, typically late adolescence or early adult life.
Clinical features
Patients with BN are usually at or near normal weight (unlike in AN), but
display a morbid fear of fatness associated with disordered eating
behaviour. They recurrently embark on eating binges, often followed by
corrective measures such as self-induced vomiting.
Diagnosis
Physical signs of repeated self-induced vomiting include pitted teeth
(from gastric acid), calluses on knuckles (‘Russell’s sign’) and parotid
gland enlargement. There are many associated physical complications,
including the dental and oesophageal consequences of repeated vomiting,
as well as electrolyte abnormalities, cardiac arrhythmias and renal
problems .
Diagnostic criteria for eating disorder
Anorexia nervosa
•
Weight loss of at least 15% of total body weight (or body mass index ≤
17.5)
•
Avoidance of high-calorie foods
•
Distortion of body image so that patients regard themselves as fat even
when grossly underweight
•
Amenorrhoea for at least 3 months
Bulimia nervosa
•
Recurrent bouts of binge eating
•
Lack of self-control over eating during binges
•
Self-induced vomiting, purgation or dieting after binges
•
Weight maintained within normal limits
medical consequence of eating disorder
Cardiac
•
ECG abnormalities: T-wave inversion, ST depression and prolonged
QTc interval
•
Arrhythmias, including profound sinus bradycardia and ventricular
tachycardia
Haematological
•
Anaemia, thrombocytopenia and leucopenia
Endocrine
•
Pubertal delay or arrest
•
Growth retardation and short stature
•
Amenorrhoea
•
Sick euthyroid state
Metabolic
•
Uraemia
•
Renal calculi
•
Osteoporosis
Gastrointestinal
•
Constipation
•
Abnormal liver function tests
Investigations
Self-induced vomiting and/or abuse of laxatives and diuretics can lead to
clinically significant electrolyte disturbances, including hypokalaemia
leading to cardiac arrhythmias. Hence it is good practice to measure urea
and electrolytes and obtain an ECG whenever these behaviours are
prominent in any patient and when BN is suspected in any medical
inpatient.
Repeated vomiting can also give rise to Mallory–Weiss tears and even
oesophageal rupture; if symptoms are suggestive of these, an endoscopy
should be performed.
Management
Treatment of bulimia with CBT achieves both short-term and long-term
improvements.
There is also evidence for benefit from the SSRI fluoxetine, but high
doses of up to 60 mg daily may be required for a prolonged period of up
to 1 year; this appears to be independent of the antidepressant effect.
Prognosis
Bulimia is not associated with increased mortality but a proportion of
sufferers go on to develop anorexia. At 10-year follow-up, approximately
10% are still unwell, 20% have a subclinical degree of bulimia, and the
remainder have recovered