A 32-year-old man with OCD presents with contamination obsessions and washing compulsions. Which feature most reliably distinguishes his condition from Body Dysmorphic Disorder (BDD) also presenting with intrusive thoughts about appearance?

## Distinguishing OCD from Body Dysmorphic Disorder (BDD) ### Overlapping Phenomenology and Key Discriminator **Key Point:** Both OCD and BDD feature ego-dystonic intrusive thoughts, poor insight, and repetitive behaviors. The critical discriminator is the **functional purpose of the compulsions/repetitive behaviors**. ### Feature Comparison Table | Feature | OCD | BDD | | --- | --- | --- | | **Obsession content** | Contamination, harm, symmetry, intrusive thoughts | Perceived defects in appearance (minor or imagined) | | **Insight** | Recognizes obsessions are irrational | Poor insight; often believes defect is real and noticeable | | **Compulsions** | Ritualistic acts to neutralize anxiety (washing, checking, arranging) | Appearance-focused repetitive behaviors (mirror checking, grooming, comparing) | | **Purpose of repetitions** | Reduce anxiety/distress from obsession | Verify or improve appearance; seek reassurance about looks | | **Distress source** | Anxiety from obsession itself | Distress from perceived appearance defect | | **Relationship to body focus** | May have OCD about contamination of body, but not about appearance per se | Preoccupation with appearance is the core obsession | ### Why Option 2 is Correct **High-Yield:** In OCD, compulsions are **anxiety-reduction rituals** (e.g., washing to neutralize contamination fear, checking to prevent harm). In BDD, repetitive behaviors are **appearance-verification or improvement rituals** (e.g., mirror checking, skin picking, comparing appearance to others). **Clinical Pearl:** A patient with OCD who washes hands due to contamination fear is performing a compulsion to reduce anxiety. A patient with BDD who checks the mirror 50 times daily is seeking reassurance about appearance; the behavior is driven by appearance preoccupation, not anxiety reduction from an unrelated obsession. ### Diagnostic Anchor **Mnemonic: OCDBDD** - **OCD:** Obsessions (unwanted thoughts) → Compulsions (anxiety-reducing rituals) - **BDD:** Body preoccupation → Appearance-focused repetitive behaviors (mirror checking, grooming, camouflaging) BDD is now classified in the "Obsessive-Compulsive and Related Disorders" category in DSM-5, but it is distinct from OCD because: 1. The obsession is about appearance, not contamination/harm/symmetry 2. The repetitive behaviors serve appearance verification, not anxiety neutralization 3. Insight is typically poorer in BDD [cite:DSM-5 Diagnostic and Statistical Manual of Mental Disorders]