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OCD — Diagnosis & Treatment

ERP plus high-dose SSRIs together outperform either alone

Field: Mental HealthCode: MH-03BUpdated: June 2026Reference: RANZCP / Aust Prescr 2015
ERP combined with an SSRI outperforms either alone. Higher-than-antidepressant SSRI doses are usually needed, and response is slower than for depression — counsel patience over 8–12 weeks.

Diagnostic features

  • Obsessions (intrusive, distressing thoughts, images or impulses) plus compulsions (repetitive behaviours to reduce the distress) — ranked among the most disabling conditions globally.
  • Often mistaken for anxiety alone, or kept secret for years through embarrassment — ask directly about checking, contamination, symmetry or intrusive thoughts if suspected.

Treatment approach

  • ERP (exposure and response prevention): specialised CBT, the best-evidenced psychotherapy — graded exposure with the compulsive response prevented.
  • Combine where possible: ERP plus an SSRI is more effective than either alone, particularly for moderate–severe symptoms.
  • Continue successful treatment ≥12 months: relapse rates exceed 50% within weeks of early discontinuation; taper slowly with specialist input.

SSRI dosing

  • Higher doses than for depression are usually needed — e.g. fluoxetine up to 80mg, sertraline up to 200mg; increase roughly every 2 weeks as tolerated.
  • Full effect may take up to 12 weeks at the therapeutic dose — counsel patience before concluding a trial has failed.
  • ECG is recommended following dose escalation with a high-dose SSRI or clomipramine — both can prolong the QT interval.
  • Clomipramine is an option after 2 failed SSRI trials, usually with specialist input given its tolerability profile.
Practical resources & share-care. Annual physical health review — cardiometabolic risk is higher in chronic mental illness. Coordinate care under a mental health treatment plan; confirm current item numbers at mbsonline.gov.au. Resources: Phoenix Australia (phoenixaustralia.org), Open Arms 1800 011 046 (veterans), SANE Australia (sane.org), Black Dog Institute (blackdoginstitute.org.au), mood-charting apps (DBSA, eMoods).

Safety

  • ECG before and after dose escalation with a high-dose SSRI or clomipramine — both can prolong the QT interval.
  • Warn about serotonin syndrome with St John's wort or tramadol alongside a high-dose SSRI.
  • Don't withdraw a successful SSRI abruptly — taper slowly; relapse rates exceed 50% within weeks of early discontinuation.

Red flags / refer

  • Severe or treatment-resistant OCD (failed 2 SSRI trials at maximum tolerated dose) → psychiatry referral; consider clomipramine or augmentation.
  • ERP unavailable locally or inaccessible → consider an internet-based ERP/CBT program as an interim option.
  • Diagnostic uncertainty, or a comorbid severe mental health condition → specialist co-assessment.

MH-03B v1.0 · Reviewed Jun 2026 · Review Jun 2027

For health-professional use. Framework: RANZCP; OCD management, Brakoulias, Aust Prescr 2015;38:121-3. Companion sheet: MH-03A PTSD — Diagnosis & Trauma-Focused Care.