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Anorexia nervosa matters because it carries the highest mortality of any psychiatric disorder, driven by the physical complications of severe self-imposed starvation. It is diagnosed as persistent restriction of food intake leading to a significantly low body weight, combined with an intense fear of gaining weight and a disturbance in how the person experiences their own body shape. For example, imagine a young woman who eats barely enough to survive yet still describes herself as overweight despite a dangerously low weight. In practice, that mismatch between actual weight and perceived body image is central to the diagnosis.

Two subtypes exist. The restricting subtype loses weight from dieting, fasting or excessive exercise alone, while the binge-purge subtype also has recurrent episodes of binge eating or purging behaviour, such as self-induced vomiting or laxative misuse. Complications include amenorrhoea (absence of menstrual periods), bradycardia (an abnormally slow heart rate), osteoporosis (weakened, brittle bones), and electrolyte disturbance, especially in the binge-purge subtype. Take two patients at the same low weight: one exercises compulsively but never binges (restricting subtype), the other binges then vomits weekly (binge-purge subtype). In practice, both subtypes share the same weight and fear criteria, but the binge-purge subtype carries extra electrolyte risk from purging.

• A severely underweight patient with anorexia nervosa begins refeeding. Which blood result most needs urgent monitoring in the first days?
• Which psychological treatment does NICE recommend first for an adult with anorexia nervosa?
• Which statement about mortality in anorexia nervosa is accurate?

• Avoidant/restrictive food intake disorder, restriction from sensory dislike, low interest, or fear of choking, unlike anorexia nervosa's restriction driven by fear of weight gain.
• Bulimia nervosa, weight is typically normal or above normal, whereas anorexia nervosa requires a significantly low body weight.
• Binge eating disorder, no compensatory behaviour and no drive for low weight, unlike anorexia nervosa's weight-loss goal.
• Anorexia nervosa, carries the highest mortality of any psychiatric disorder, rather than the comparatively lower physical-complication burden of bulimia nervosa.

• Bilirubin reflects liver and haemolytic problems rather than the refeeding shift.
• Urate rises in gout and tumour lysis rather than in refeeding syndrome.
• Eye movement desensitisation is a treatment for post-traumatic stress disorder.
• Dialectical behaviour therapy targets emotional dysregulation and self-harm rather than serving as first-line here.
• Relaxation training does not address the eating disorder psychopathology.

• Extract the defining phenomenology, duration, severity and functional-impact clues.
• Match the pattern to the most specific diagnostic or assessment construct.
• Actively test the closest look-alike against the missing or contradictory clue.
• Choose the precise term rather than a broader category that is merely compatible.