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OCD vs OCPD - Complete Clinical Reference

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PART 1: OCD vs OCPD - Key Differences

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PART 2: Classification of OCD

DSM-IV (1994)

• Chapter: Anxiety Disorders
• Code: 300.3
• Diagnostic Criteria:
  • (A) Either obsessions OR compulsions:
    • Obsessions: Recurrent, persistent thoughts/impulses/images that are intrusive, causing marked anxiety; not simply excessive worry; person tries to ignore, suppress, or neutralize them; recognized as products of their own mind (not thought insertion)
    • Compulsions: Repetitive behaviors (hand washing, ordering, checking) or mental acts (praying, counting, silently repeating words) performed in response to an obsession or according to rigid rules; aimed at preventing distress or a dreaded event; clearly excessive or not realistically connected to what they are meant to prevent
  • (B) At some point, the person has recognized that the obsessions or compulsions are excessive or unreasonable (this was removed in DSM-5)
  • (C) Causes marked distress, is time-consuming (>1 hour/day), or significantly interferes with normal routines, occupational/academic functioning, or social activities/relationships
  • (D) Not restricted to another Axis I disorder (if present, content not restricted to that disorder)
  • (E) Not due to direct physiological effects of a substance or GMC
• Specifier: "With poor insight" - if most of the time during current episode, person does not recognize obsessions/compulsions as excessive or unreasonable

DSM-5 (2013) - Major Differences from DSM-IV

• Chapter: NEW standalone chapter - "Obsessive-Compulsive and Related Disorders" (removed from Anxiety Disorders)
• Code: 300.3 (F42.2)
• Changes from DSM-IV:
  1. Removed requirement that patient recognize symptoms as "excessive or unreasonable" - now covers full spectrum including delusional conviction
  2. Obsessions redefined to include thoughts, urges, or images (not impulses)
  3. Explicitly states compulsions can be behavioral or mental acts
  4. Emphasizes functional relationship between obsessions and compulsions
  5. Added more specific exclusion criteria to differentiate OCD from other disorders
• Specifiers (new):
  • Insight level: Good or fair insight | Poor insight | Absent insight/delusional beliefs (when OCD beliefs are held with delusional intensity)
  • Tic-related specifier: With/without current or past history of tic disorder
• OCD-Related Disorders in same chapter:
  1. Body dysmorphic disorder
  2. Hoarding disorder (new in DSM-5)
  3. Trichotillomania (hair-pulling disorder)
  4. Excoriation (skin-picking) disorder (new in DSM-5)
  5. Substance/medication-induced OCRD
  6. OCRD due to another medical condition
  7. Other specified / unspecified OCRD

ICD-10 (WHO, in use until 2022)

• Chapter: F4 - "Neurotic, Stress-related and Somatoform Disorders"
• Code: F42 with subtypes:
  • F42.0 - Predominantly obsessional thoughts or ruminations
  • F42.1 - Predominantly compulsive acts (obsessional rituals)
  • F42.2 - Mixed obsessional thoughts and acts
  • F42.8 - Other obsessive-compulsive disorders
  • F42.9 - OCD, unspecified
• Key features:
  • Remains grouped with neurotic/anxiety disorders under F40-F48
  • Does NOT require a functional relationship between obsessions and compulsions
  • Does NOT mention mental rituals - only behavioral compulsions recognized
  • Uses descriptive guidelines rather than strict operationalized criteria
  • Specifiers are content-based (obsessions vs compulsions vs mixed)
  • No insight specifier
  • OCD and anxiety disorders are in the same grouping

ICD-11 (WHO, 2022 - current)

• Chapter: NEW separate chapter - "Obsessive-Compulsive or Related Disorders" (convergence with DSM-5 approach)
• Code: 6B20 - Obsessive-Compulsive Disorder
• Key changes from ICD-10:
  1. OCD given its own separate chapter - removed from anxiety/neurotic group
  2. Insight specifier added (converging with DSM-5)
  3. Mental rituals now recognized as compulsions
  4. Functional link between obsessions and compulsions now emphasized
  5. ICD-11 includes additional disorders not in DSM-5 OCRDs:
• Related disorders in the ICD-11 OCD chapter:

Comparison Table: All 4 Systems

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PART 3: Treatment-Resistant OCD - Criteria

Operational Definitions

• At least 12 weeks of treatment at the highest tolerated dose of an SSRI or clomipramine
• PLUS at least 30 hours of CBT/ERP

• 3-6 months of at least 3 antidepressants including clomipramine
• PLUS at least 2 augmentation trials with atypical antipsychotics

• Full response = ≥35% Y-BOCS reduction
• Partial response = 25-35% reduction
• Non-response = <25% reduction
• Severe OCD (threshold for surgical consideration) = Y-BOCS ≥28

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PART 4: Maximum Drug Doses in OCD

First-Line: SSRIs (FDA-Approved for OCD)

First-Line / Gold Standard: Clomipramine (TCA)

Second-Line Augmentation: Antipsychotics (Atypical)

Glutamatergic Augmentation (Severely Resistant Cases)

Other Adjunctive Agents

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PART 5: Treatment Flow Algorithm

CONFIRMED OCD DIAGNOSIS
        │
        ▼
STEP 1 - FIRST-LINE (Any SSRI + ERP)
├── Choose SSRI (fluvoxamine, fluoxetine, sertraline, paroxetine, or escitalopram)
├── Start low, titrate to standard maximum dose over 4-6 weeks
├── CBT with Exposure and Response Prevention (ERP): 13-20 sessions
├── Duration: 12 weeks (minimum 4-6 weeks at max tolerated dose)
├── RESPONSE (≥35% Y-BOCS reduction) → CONTINUE 1-2 years maintenance
└── PARTIAL/NO RESPONSE → STEP 2

STEP 2 - DOSE OPTIMIZATION
├── Titrate SSRI to maximum anti-obsessional dose or supratherapeutic dose
│   (e.g., sertraline to 400 mg, fluoxetine to 120 mg)
├── Intensify ERP sessions
├── Additional 4-8 weeks at higher dose
├── RESPONSE → Maintain
└── NO RESPONSE → STEP 3

STEP 3 - SWITCH AGENT
├── Option A: Switch to a different SSRI (full dose trial, 12 weeks)
├── Option B: Switch to CLOMIPRAMINE (most efficacious; titrate to max 250 mg;
│   monitor ECG and plasma levels; keep combined level <500 ng/mL)
├── Continue ERP
├── RESPONSE → Maintain
└── NO RESPONSE = TREATMENT-RESISTANT OCD CRITERIA NOW MET → STEP 4

STEP 4 - AUGMENTATION
├── 4a. Add atypical antipsychotic to SRI:
│    • Risperidone 0.5-3 mg/day (first choice - best evidence)
│      OR Aripiprazole 5-15 mg/day (preferred in young patients)
│    Duration: 8 weeks trial minimum
├── 4b. Consider adding buspirone 15-60 mg/day
├── 4c. Second full course of ERP with an INDEPENDENT therapist
│    (consensual requirement before escalating to interventional)
├── RESPONSE → Maintain
└── NO RESPONSE → STEP 5

STEP 5 - GLUTAMATERGIC / THIRD-LINE PHARMACOLOGY
├── Add memantine (up to 20 mg/day)
│   OR riluzole (up to 100 mg/day)
│   OR lamotrigine (up to 100 mg/day)
│   OR topiramate (up to 400 mg/day)
├── Each agent: 8-12 week trial
├── RESPONSE → Maintain
└── NO RESPONSE + Y-BOCS ≥28 + GAF <45 + OCD ≥5 years → STEP 6

STEP 6 - NEUROMODULATION
├── 6a. rTMS / Deep TMS (non-invasive; first neuromodulation step)
│    • Brainsway H7 coil targeting ACC/medial prefrontal cortex
│    • FDA-cleared for OCD (2018)
│    • Outpatient; well-tolerated
├── 6b. If rTMS fails → proceed to surgical evaluation
└── NO RESPONSE → STEP 7 (Neurosurgical - last resort)

STEP 7 - NEUROSURGICAL PROCEDURES
├── 7a. DEEP BRAIN STIMULATION (DBS) - PREFERRED (reversible/adjustable)
│    • Targets: ALIC/ventral striatum, subthalamic nucleus (STN)
│    • ~60% achieve ≥35% Y-BOCS reduction
│    • FDA HDE approved for severe treatment-resistant OCD
│    • Requires DBS criteria to be fully met (see above)
│
└── 7b. ABLATIVE PROCEDURES (irreversible - used if DBS unavailable/contraindicated)
     • Anterior cingulotomy (anterior cingulate cortex)
     • Anterior capsulotomy (ALIC - radiosurgery/Gamma Knife or thermal)
     • Subcaudate tractotomy (orbitofrontal-subcortical pathway)
     • Limbic leucotomy (combination of cingulotomy + subcaudate tractotomy;
       broadest intervention; highest efficacy in some series)

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Part 6: DBS Criteria Summary (Prerequisite Checklist)

• Non-response to ≥2 SSRI courses at maximum dose for ≥12 weeks each
• Non-response to ≥1 clomipramine course at maximum dose for ≥12 weeks
• Non-response to ≥1 atypical antipsychotic augmentation for ≥8 weeks
• ≥2 CBT/ERP courses (including one with an independent therapist)
• Y-BOCS score ≥28 (severe OCD at baseline)
• GAF score <45 (significant functional impairment)
• OCD duration ≥5 years
• Patient medically fit for neurosurgery
• Capacity to consent

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• Harrison's Principles of Internal Medicine 22E (2025) - OCD chapter
• Kaplan & Sadock's Synopsis of Psychiatry - OCD and Personality Disorders
• Kaplan & Sadock's Comprehensive Textbook of Psychiatry - Comparative Nosology
• Frontiers in Psychiatry 2023 (doi:10.3389/fpsyt.2023.1065812) - Therapies for OCD: Current State of the Art
• Pharmacotherapy for Treatment-Resistant OCD - J Clin Psychiatry (PMC7495343)
• OCD for ICD-11: Proposed Changes - Stein et al. (PMC5125074)
• Wolf et al. 2025 (PMID 41138314) - Neurostimulation in treatment-resistant OCD: International overview