SSRI Therapeutic Response — MRCPsych Paper B MCQ

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EasyMood DisordersSSRI Therapeutic ResponseMRCPsych Paper B

A 40-year-old man with a depressive episode has taken citalopram 20 mg daily as prescribed for 6 weeks. His mood, sleep and energy have improved, and his PHQ-9 score has fallen from 18 to 8. He has no new agitation, autonomic disturbance, neuromuscular abnormalities, rash or airway symptoms. Which term best describes his current treatment outcome?

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Correct answer: B — Clinical response without remission

The best answer is B. His PHQ-9 has fallen by 10 points, representing a 55.6% improvement. NICE evidence reviews usually define response as at least a 50% reduction from baseline. However, a PHQ-9 of 8 indicates residual depressive symptoms, so this is response without remission rather than a “full therapeutic response.” Activation would involve new anxiety, agitation or restlessness. Serotonin toxicity requires a compatible combination of mental-state change, autonomic disturbance and neuromuscular findings. A hypersensitivity reaction would involve features such as rash, angioedema or airway compromise. Non-response is contradicted by both the symptom improvement and rating-scale reduction. NICE advises continuing effective antidepressant treatment for at least 6 months after remission, with regular review.

Reference: NICE, Depression in adults: treatment and management (NG222), Evidence review B: Treatment of a new episode of depression, updated 2024. https://www.nice.org.uk/guidance/ng222/evidence/b-treatment-of-a-new-episode-of-depression-pdf-11131004415