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Clinical Scenario
A 24-year-old university student presents to her GP with a 6-month history of increasingly distressing intrusive thoughts about contamination. She believes her hands are "covered in germs" after touching any surface and washes them over 30 times per day, each wash lasting 5 to 10 minutes. Her hands are red, cracked and bleeding. She acknowledges the thoughts are "irrational" but says she feels "overwhelming anxiety" if she tries to resist washing. She has started avoiding public transport and skipping lectures. She scores 23 on the Y-BOCS. She has no psychiatric history but her aunt has OCD.
Questions
a) What is the diagnosis and what two DSM-5-TR criteria support it? (2 marks)
Diagnosis: Obsessive-compulsive disorder (OCD).
DSM-5-TR criteria:
- Presence of obsessions (intrusive, recurrent, unwanted thoughts/images causing marked anxiety — contamination fears) and/or compulsions (repetitive behaviours aimed at reducing anxiety — hand washing)
- Time-consuming (over 1 hour per day) or causing clinically significant distress/impairment (avoiding public transport, skipping lectures)
Additional: insight present (recognises as irrational) — distinguishes from psychosis/delusional disorder.
b) Outline the first-line management plan. (3 marks)
- ERP (Exposure and Response Prevention) — first-line psychological therapy; expose to contamination triggers (e.g., touching doorknobs) and prevent the compulsive wash; 13-20 weekly sessions; 60-80% improvement
- SSRI at HIGH dose — fluoxetine 60 mg OD or sertraline 200 mg OD (higher than depression doses); onset of action 8-12 weeks; combine with ERP for moderate-to-severe cases
- Psychoeducation — explain the CSTC circuit model, ego-dystonic nature, that OCD is a neurobiological disorder (not a character flaw), expected timeline for SSRI response
c) Name two pharmacological options if first-line SSRI fails after 12 weeks. (2 marks)
- Switch to another SSRI (e.g., fluvoxamine up to 300 mg) or clomipramine 100-250 mg (TCA; monitor ECG and LFTs)
- Antipsychotic augmentation — aripiprazole 5-15 mg or risperidone 0.5-2 mg added to ongoing SSRI (evidence: 30-50% partial response)
d) What is the significance of the family history? (1 mark)
First-degree relatives of OCD patients have a 3-5x higher risk of OCD. Heritability is approximately 45-65% in twin studies. Genes implicated include SLC1A1 (glutamate transporter) and SLC6A4 (serotonin transporter). This supports the neurobiological model and informs genetic counselling.
e) What referral pathway should the GP initiate? (2 marks)
- Urgent referral to community mental health team (CMHT) for specialist ERP (IAPT Step 3/4) and psychiatric medication review
- Dermatology referral for the hand dermatitis (contact irritant dermatitis from excessive washing) — treat with emollients and topical steroids
- Consider university disability support for academic accommodations during treatment
Examiner Notes
- Common error: prescribing benzodiazepines — not recommended for OCD (no evidence, addiction risk)
- Common error: using depression-dose SSRIs — OCD requires higher doses (fluoxetine 60 mg, not 20 mg)
- Key discriminator tested: ego-dystonic (OCD) vs ego-syntonic (OCPD)
- Y-BOCS score of 23 = severe OCD (thresholds: 0-7 subclinical, 8-15 mild, 16-23 moderate, 24-31 severe, 32-40 extreme)