What is the most appropriate diagnostic approach for a patient with suspected obsessive-compulsive disorder (OCD), considering their age, medical history, including any history of trauma, anxiety, or depression?

How to Diagnose OCD

Diagnose OCD when a patient presents with obsessions and/or compulsions consuming more than 1 hour per day AND causing clinically significant distress or functional impairment, after ruling out that symptoms are better explained by another mental disorder, substance use, or medical condition. 1

Step 1: Conduct a Detailed Psychiatric History and Mental Status Examination

The foundation of OCD diagnosis is a comprehensive psychiatric history and mental status examination. 2 This is your primary diagnostic tool before using any structured instruments.

Key Elements to Assess:

Obsessions - Look for recurrent, persistent, intrusive thoughts, urges, images, or impulses that are:

• Ego-dystonic (experienced as unwanted and inconsistent with self) 1
• Recognized by the patient as excessive or unreasonable 1
• Anxiety-provoking 1
• Typically involving themes of contamination, harm, symmetry, or forbidden thoughts 1

Compulsions - Look for repetitive, purposeful, intentional behaviors or mental acts that are:

• Performed in response to an obsession or in a stereotyped fashion 1
• Done to reduce anxiety or prevent dreaded outcomes 1
• Recognized by the patient as excessive or unreasonable 1
• Examples include checking, washing, counting, ordering, or mental rituals 3

Step 2: Apply the Critical Time and Impairment Criteria

Both of these must be present:

• Symptoms consume more than 1 hour per day 1
• Symptoms cause substantial distress or functional impairment in work, family, or social domains 1

This threshold is essential because intrusive thoughts and repetitive behaviors are common in the general population, and rituals are normal parts of development. 1

Step 3: Rule Out Differential Diagnoses

Generalized Anxiety Disorder/Depression:

• GAD worries are about real-life concerns and are more ego-syntonic (acceptable to self) 2
• GAD lacks the compulsive rituals seen in OCD 4
• Depression ruminations are less irrational than OCD obsessions 2

Autism Spectrum Disorder:

• ASD rumination is ego-syntonic and comfortable, whereas OCD rumination is ego-dystonic and distressing 1

Schizotypal Personality Disorder:

• Look for pervasive pattern of referential ideas and magical thinking across situations, not just limited to OCD rituals 5
• Schizotypal features include social/interpersonal deficits and odd beliefs beyond OCD symptoms 5

Substance Use or Medical Conditions:

• Rule out that symptoms are substance-induced or due to another medical condition 1

History of Trauma:

• Childhood trauma in OCD patients is associated with more severe anxiety, higher impulsivity, and higher prevalence of comorbid ADHD 6
• Trauma history predicts comorbidities but has indirect effects on OCD severity 6

Step 4: Use Structured Diagnostic Instruments

For Adults:

• Structured Clinical Interview for DSM-5 (SCID-5) - Clinician or Research version 2, 1
• Anxiety Disorders Interview Schedule for DSM-5 (ADIS-5) - Adult version 2, 1
• Mini International Neuropsychiatric Interview (MINI 7.0) - Shorter alternative 2

For Children/Adolescents:

• ADIS-5 Child or Parent version 2, 1
• MINI for children/adolescents 2

Step 5: Quantify Symptom Severity

Yale-Brown Obsessive-Compulsive Scale (Y-BOCS):

• Use Y-BOCS for adults or Children's Y-BOCS (CY-BOCS) for youth 2, 1
• Scores ≥14 indicate clinically significant OCD requiring treatment 1
• Includes both a symptom checklist and severity scale 2
• Available in self-report format 2

Alternative Severity Measures:

• Dimensional Y-BOCS (DY-BOCS) - Allows more detailed assessment of OCD symptom dimensions 2
• Florida Obsessive-Compulsive Inventory (FOCI) - Shorter option with symptom checklist and 5 severity items 2

Step 6: Document Important Specifiers

Insight Level (required by DSM-5):

• Good or fair insight 1
• Poor insight 1
• Absent insight/delusional beliefs 1

Tic Specifier:

• Document current or past tic disorder 1

Comorbid Conditions:

• Depression co-occurs commonly with OCD 1, 7
• Anxiety disorders co-occur in approximately 90% of individuals with lifetime OCD 4
• Both diagnoses can be made when obsessions/compulsions are distinct from anxiety symptoms and each causes independent functional impairment 4

Step 7: Assess Family Accommodation

Evaluate family behaviors that facilitate OCD symptoms:

• Providing reassurance in response to obsessive doubts 2
• Assisting with avoidance behaviors 2
• Participating in rituals 2

Family accommodation measures can be useful for comprehensive assessment and treatment planning. 2

Common Pitfalls to Avoid

Don't dismiss symptoms because patients conceal them - OCD patients often attempt to hide their symptoms, so screen for OCD in every mental status examination. 7

Don't confuse normal intrusive thoughts with OCD - The key differentiators are the >1 hour/day threshold and substantial distress/impairment. 1

Don't overlook the ego-dystonic nature - This distinguishes OCD from substance use disorders, addictive disorders, and paraphilias, which have ego-syntonic, gratifying components. 2

Don't miss comorbid depression - Depression is the most common complication of OCD and requires assessment. 7