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Antidepressant Selection — MRCPsych Paper B MCQ

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ModerateMood DisordersAntidepressant SelectionMRCPsych Paper B

A 30-year-old woman has a major depressive episode with anhedonia, psychomotor retardation, early-morning wakening, reduced appetite and clinically significant weight loss. The diagnosis has been reviewed, and no comorbid condition or adherence problem explains the poor response. She has had no meaningful improvement after two different SSRIs, each taken at a therapeutic dose for 6 weeks with good adherence. She would prefer an antidepressant likely to improve sleep and appetite and accepts the possibility of sedation and weight gain. Which antidepressant is most appropriate?

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Correct answer: E — Mirtazapine

Mirtazapine is the best choice. After two adequate SSRI trials, NICE supports switching antidepressants, including switching to a different class, according to clinical needs and patient preferences. Mirtazapine is particularly well matched here because H1 antagonism produces sedation, while increased appetite and weight gain are very common effects; these may be advantageous in depression with marked insomnia and weight loss. Fluoxetine, sertraline and citalopram are SSRIs, so a third SSRI is less compelling after two adequate failures. Venlafaxine is a reasonable further-line SNRI and is the strongest distractor, but insomnia is a very common adverse effect and reduced appetite is common, making it less suitable for this patient's stated priorities. The melancholic symptoms establish severity but do not alone mandate a specific antidepressant.

Reference: Electronic Medicines Compendium, Mirtazapine 30 mg tablets, SmPC sections 4.1, 4.2, 4.8 and 5.1, updated 2025: https://www.medicines.org.uk/emc/product/100083/smpc