Residency · Residency · Psychiatry

Obsessive-Compulsive Disorder: Pharmacotherapy and ERP

Diagnosis

DSM-5-TR Criteria

Presence of obsessions, compulsions, or both: Obsessions: recurrent, persistent, intrusive, unwanted thoughts, urges, or images that cause marked anxiety or distress; the individual attempts to ignore, suppress, or neutralize them. Compulsions: repetitive behaviors (hand washing, ordering, checking) or mental acts (praying, counting, repeating words silently) performed in response to an obsession or according to rigid rules; aimed at preventing anxiety or a dreaded event, but not connected in a realistic way or clearly excessive. Obsessions/compulsions are time-consuming (>=1 hour/day) or cause significant distress or functional impairment. Not attributable to substance use or another medical condition. Not better explained by another mental disorder.

Insight Specifier

Good or fair insight: recognizes OCD beliefs are definitely or probably not true. Poor insight: thinks OCD beliefs are probably true. Absent insight/delusional beliefs: completely convinced OCD beliefs are true. Poor insight is associated with worse treatment response and may be confused with psychotic disorders.

Common Obsession Themes

Contamination (most common) Symmetry/ordering/exactness. Forbidden/taboo thoughts (aggressive, sexual, religious -- "pure O") Harm (fear of causing harm to self or others) Need for certainty/doubt ("did I lock the door?")

Common Compulsion Types

Washing/cleaning. Checking. Ordering/arranging. Mental rituals (counting, praying, repeating) Reassurance-seeking. Avoidance (while not technically a compulsion, avoidance is a functionally equivalent behavior)

Yale-Brown Obsessive Compulsive Scale (Y-BOCS)

Gold standard clinician-rated severity measure. 10 items: 5 for obsessions, 5 for compulsions (time, interference, distress, resistance, control) Scores: 0-7 subclinical, 8-15 mild, 16-23 moderate, 24-31 severe, 32-40 extreme. Used to track treatment response; >=35% reduction = responder.

OCD Presenting as Depression

Many patients with OCD present to psychiatry with depression as their chief complaint. OCD is frequently comorbid with MDD (~67% lifetime comorbidity) Patients may not volunteer obsessions/compulsions due to shame, poor insight, or egodystonic nature of symptoms. Screen for OCD in all patients presenting with depression -- especially if depression is treatment-resistant. Clues: excessive hand washing, lengthy bedtime rituals, difficulty leaving the house on time, avoidance of specific triggers, intrusive thoughts causing distress. Appropriate screening question: "Do you have thoughts that keep coming into your mind that you find upsetting or hard to get rid of?" or "Are there things you feel you have to do over and over?".

Pharmacotherapy

Serotonin Reuptake Inhibitors (SRIs)

SRIs are the first-line pharmacotherapy for OCD. Key difference from depression dosing: OCD typically requires HIGHER doses and LONGER trials. | SRI Agent | OCD Dose Range | MDD Dose Range | FDA-Approved for OCD | Notes |

Adequate trial duration: 8-12 weeks at maximum tolerated dose (longer than for depression) Response rates: approximately 40-60% with adequate SRI trial. Clomipramine may be the most effective single agent but is usually second-line due to side effects (anticholinergic, cardiac, seizure risk at high doses)

Augmentation with Low-Dose Antipsychotics

For SRI non-responders or partial responders. Evidence-based augmentation: low-dose risperidone (0.5-2 mg), aripiprazole (2.5-10 mg), or haloperidol. Approximately 30% of SRI non-responders will respond to antipsychotic augmentation. Limited duration trials suggest benefit; consider time-limited augmentation with reassessment. Most effective in patients with comorbid tic disorders or poor insight.

Other Augmentation Strategies

Glutamatergic agents: memantine, N-acetylcysteine, riluzole -- emerging evidence, not standard of care. IV clomipramine: used in specialized centers for refractory cases. Lithium, buspirone: limited evidence for OCD augmentation (unlike in depression)

Exposure and Response Prevention (ERP)

Principles

ERP is the first-line psychotherapy for OCD and the most effective psychological treatment. Exposure: systematic, graduated confrontation with feared obsessional stimuli. Response prevention: deliberate abstention from compulsive behaviors during and after exposure. Theoretical basis: habituation model (anxiety decreases with prolonged exposure) and inhibitory learning model (new non-threat associations are formed)

ERP Protocol

Psychoeducation: explain the OCD cycle (obsession --> anxiety --> compulsion --> temporary relief --> reinforcement) Hierarchy construction: patient and therapist collaboratively create a fear hierarchy using Subjective Units of Distress (SUDS) ratings from 0-100. Graduated exposure: begin with moderate-difficulty items; progress to more challenging exposures as habituation occurs. In vivo exposure: real-world exposure to feared stimuli (e.g., touching a "contaminated" doorknob) Imaginal exposure: mentally rehearsing feared scenarios (e.g., for harm obsessions where real exposure is not possible) Response prevention: explicit agreement not to perform compulsions during and after exposure sessions. Between-session practice: daily self-directed exposure homework is essential for generalization.

Efficacy

ERP response rates: 60-70% (higher than pharmacotherapy alone) Combination ERP + SRI may be superior to either alone, especially for moderate-severe OCD. ERP has better long-term durability than pharmacotherapy (lower relapse after discontinuation) Attrition rate: approximately 25% (exposure is anxiety-provoking by design)

Barriers and Adaptations

Therapist shortage: ERP requires specialized training; many CBT therapists are not trained in ERP. Technology-assisted ERP: teletherapy, app-based tools, and virtual reality are expanding access. Intensive ERP programs: daily sessions over 2-3 weeks for severe or treatment-resistant cases. Family involvement: reducing family accommodation (performing compulsions on behalf of or participating in rituals with the patient) is critical.

<image> A diagram of the OCD cycle and how ERP breaks it. Show a circular cycle: obsessive thought (intrusive image/urge) --> anxiety/distress --> compulsive behavior --> temporary relief --> reinforcement of obsession. Then show how ERP interrupts the cycle: exposure maintains contact with the obsessional trigger while response prevention blocks the compulsion, allowing anxiety to habituate naturally over time. Include a graph showing the anxiety curve during exposure (rises initially, then decreases with prolonged exposure -- habituation) vs. the anxiety curve with compulsion (brief reduction followed by return). Clinical psychotherapy education style. </image>

<image> A sample ERP hierarchy chart for a patient with contamination OCD. Show a vertical ladder or thermometer with SUDS ratings from 0-100. List example exposure tasks at each level: touching a light switch without washing (SUDS 30), shaking hands (SUDS 45), touching a public doorknob (SUDS 60), touching a bathroom faucet (SUDS 75), touching a toilet seat and eating food without washing (SUDS 90). Include annotations showing the progression through the hierarchy and the therapist's role at each step. Clean clinical format. </image>

<image> A treatment algorithm for OCD. Start with "OCD diagnosed (Y-BOCS >=16)." Branch into mild-moderate (ERP first-line) and moderate-severe (ERP + SRI combination). Show SRI titration to maximum tolerated dose with 8-12 week trial. If inadequate response: augment SRI with low-dose antipsychotic, consider switching SRI or trying clomipramine. For treatment-resistant cases: intensive ERP programs, neurosurgical approaches (DBS, gamma knife capsulotomy). Include Y-BOCS response thresholds at each decision point. Color-coded by treatment modality. </image>

Clinical Pearls

OCD requires higher SRI doses and longer trial durations than depression -- do not declare treatment failure without reaching maximum tolerated doses for 8-12 weeks. ERP is the most effective treatment for OCD and should be offered to every patient; medication alone is insufficient for many patients. Always screen for OCD in treatment-resistant depression -- OCD may be the primary undiagnosed condition driving the depressive symptoms. Patients with "pure O" (obsessions without visible compulsions) are doing mental rituals -- they still benefit from ERP targeting these covert compulsions. Family accommodation (participating in or facilitating the patient's rituals) maintains OCD -- family psychoeducation and reducing accommodation are essential components of treatment. Low-dose antipsychotic augmentation is the strongest evidence-based pharmacologic augmentation strategy for SRI-resistant OCD. Clomipramine may be the most potent single agent for OCD but is typically second-line due to TCA side effects; it can be used as augmentation of an SSRI (monitor levels and cardiac effects)

References

• APA Practice Guidelines for the Treatment of OCD. Am J Psychiatry. 2007;164(7 Suppl):5-53.
• Foa EB, et al. Exposure and Response (Ritual) Prevention for Obsessive-Compulsive Disorder: Therapist Guide. 2nd ed. Oxford University Press; 2012.
• Skapinakis P, et al. Pharmacological and psychotherapeutic interventions for management of OCD in adults: a systematic review and network meta-analysis. Lancet Psychiatry. 2016;3(8):730-739.
• Bloch MH, et al. Meta-analysis of the dose-response relationship of SSRI in obsessive-compulsive disorder. Mol Psychiatry. 2010;15(8):850-855.
• Veale D, et al. Atypical antipsychotic augmentation in SSRI treatment refractory OCD: a systematic review and meta-analysis. BMC Psychiatry. 2014;14:317.

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