Obsessive-Compulsive and Related Disorders (OCRDs)

Introduction to OCRDs for MCCQE1

Obsessive-Compulsive and Related Disorders (OCRDs) represent a cluster of conditions characterized by repetitive thoughts and/or behaviors. For the MCCQE1, candidates must demonstrate the ability to distinguish these disorders from anxiety disorders, psychotic disorders, and personality disorders (specifically OCPD).

Understanding the CanMEDS roles is vital here:

Medical Expert: Correctly diagnosing based on DSM-5-TR criteria and selecting evidence-based treatments (CBT-ERP and Pharmacotherapy).
Communicator: Establishing a therapeutic alliance, as patients often hide symptoms due to shame or stigma.

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Canadian Context: In Canada, access to specialized psychotherapy (CBT) can be limited by geography and cost. Family physicians often manage the initial pharmacological treatment while navigating waitlists for psychiatric services.

Etiology and Pathophysiology

While the exact etiology is unknown, current evidence suggests a multifactorial origin involving genetic, environmental, and neurobiological factors.

Neurobiology: Dysregulation of the Cortico-Striato-Thalamo-Cortical (CSTC) loop.
Neurotransmitters: Serotonin (5-HT), Dopamine, and Glutamate.
Genetics: Higher concordance in monozygotic twins.
PANDAS/PANS: Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (rare but high-yield for pediatric presentations).

Obsessive-Compulsive Disorder (OCD)

OCD is defined by the presence of obsessions, compulsions, or both.

Clinical Features

Obsessions

Obsessions are recurrent, persistent thoughts, urges, or images that are intrusive and unwanted. They cause marked anxiety or distress. Common themes include contamination, pathological doubt, need for symmetry, and aggressive/sexual thoughts.

Diagnosis (DSM-5-TR Criteria)

To diagnose OCD for MCCQE1 purposes, look for:

Presence of Obsessions, Compulsions, or both.
They are time-consuming (e.g., take > 1 hour per day) OR cause clinically significant distress/impairment.
Not attributable to a substance or another medical condition.

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Key Concept: In OCD, the obsessions are typically Ego-Dystonic (inconsistent with the patient’s self-image), causing distress. In Obsessive-Compulsive Personality Disorder (OCPD), the behaviors are Ego-Syntonic (viewed as correct or desirable).

Differential Diagnosis: OCD vs. OCPD

This is a classic MCCQE1 distinction.

Feature	Obsessive-Compulsive Disorder (OCD)	Obsessive-Compulsive Personality Disorder (OCPD)
Nature of Symptoms	Intrusive thoughts/rituals	Pervasive pattern of perfectionism/control
Patient Attitude	Ego-dystonic (distressed by them)	Ego-syntonic (believes they are “right”)
Time Course	Waxing and waning	Chronic, stable trait
Functionality	Often impairs efficiency due to rituals	Impairs efficiency due to perfectionism
Treatment Response	Responds to SSRIs & ERP	Responds poorly to meds; requires long-term therapy

Body Dysmorphic Disorder (BDD)

Preoccupation with one or more perceived defects or flaws in physical appearance that are not observable or appear slight to others.
High suicide risk (must assess safety).
Canadian Practice Tip: These patients often present to dermatologists or plastic surgeons first. Surgery is generally contraindicated as it rarely satisfies the patient.

Hoarding Disorder

Persistent difficulty discarding or parting with possessions, regardless of actual value.
Results in accumulation that congests and creates unsafe living areas.
Differs from normal collecting (which is organized and pleasurable).

Trichotillomania (Hair-Pulling Disorder)

Recurrent pulling out of one’s hair, resulting in hair loss.
Repeated attempts to decrease or stop.

Excoriation (Skin-Picking) Disorder

Recurrent skin picking resulting in skin lesions.

Management and Canadian Guidelines

The Canadian Anxiety Disorders Treatment Guidelines (managed by CANMAT) recommend a stepped-care approach.

Step 1: Assessment and Psychoeducation

Confirm diagnosis, assess severity (e.g., using the Yale-Brown Obsessive Compulsive Scale - Y-BOCS), and assess for comorbidities (Depression, Tics). Educate the patient that the goal is symptom reduction, not necessarily complete elimination.

Step 2: First-Line Treatments

For mild to moderate OCD, Cognitive Behavioral Therapy (CBT) with Exposure and Response Prevention (ERP) is the gold standard.

For moderate to severe OCD, or if CBT is unavailable or declined:

SSRIs (Fluoxetine, Fluvoxamine, Sertraline, Paroxetine).
Note: OCD typically requires higher doses of SSRIs compared to depression and a longer trial duration (8-12 weeks) to see response.

Step 3: Combination Therapy

For severe symptoms or partial response to monotherapy, combine SSRI + CBT (ERP).

Step 4: Refractory Cases

If first-line SSRIs fail:

Switch to a different SSRI.
Switch to Clomipramine (TCA). Note: More side effects (anticholinergic, cardiac).
Augmentation with an antipsychotic (e.g., Risperidone, Aripiprazole) - specifically for OCD with tic disorders or partial insight.

Pharmacology Cheat Sheet for OCD

First-line: SSRIs (e.g., Sertraline, Fluoxetine).
Dosing: Often requires maximum tolerated doses (e.g., Sertraline 200mg+).
Second-line: Clomipramine (most serotonergic TCA).
Augmentation: Atypical antipsychotics (Risperidone) are useful, especially if tics are present.

Key Points to Remember for MCCQE1

PANDAS: Consider in a child with abrupt onset OCD + urinary frequency + neurological signs following a sore throat.
Suicide Risk: Always assess in BDD and severe OCD.
Ego-Dystonic: The hallmark that separates OCD from OCPD and psychotic disorders (usually).
ERP: Exposure and Response Prevention is the specific type of CBT required. General “supportive counseling” is ineffective.
Benzodiazepines: Generally not indicated for OCD treatment as they do not treat the core symptoms and may interfere with ERP.

Sample Question

Clinical Scenario

A 26-year-old male presents to his family physician complaining that his hands are raw and bleeding. He reports washing his hands 30 to 40 times a day because he is terrified of contracting a deadly illness from doorknobs. He spends approximately 3 hours daily on this ritual, which has resulted in him being late for work multiple times. He recognizes that his fear is excessive and irrational but feels intense anxiety if he tries to stop. He has no other significant medical history.

Which of the following is the most appropriate initial pharmacologic treatment?

Options

Explanation

The correct answer is:

C. Sertraline

Explanation: This patient presents with classic symptoms of Obsessive-Compulsive Disorder (OCD): obsessions (fear of contamination), compulsions (washing), time-consuming rituals (>1 hour/day), and ego-dystonic insight (recognizes it is excessive).

Sertraline (Option C) is a Selective Serotonin Reuptake Inhibitor (SSRI). SSRIs are the first-line pharmacologic treatment for OCD according to Canadian guidelines (CANMAT).
Clonazepam (Option A) is a benzodiazepine. While it may reduce acute anxiety, it does not treat the core symptoms of OCD and is not a first-line maintenance therapy.
Venlafaxine (Option B) is an SNRI. While SNRIs can be used in OCD, they are typically considered second-line after SSRIs have been tried.
Risperidone (Option D) is an atypical antipsychotic. It is used as an augmentation strategy for refractory OCD but is not a monotherapy for initial treatment.
Bupropion (Option E) acts on norepinephrine and dopamine. It is generally ineffective for OCD and can potentially exacerbate anxiety or obsessive symptoms.

References

American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders (5th ed., text rev.).
Katzman, M. A., et al. (2014). Canadian clinical practice guidelines for the management of anxiety, posttraumatic stress and obsessive-compulsive disorders. BMC Psychiatry, 14(1). [CANMAT Guidelines]
Swinson, R. P., et al. (2006). Clinical Practice Guidelines: Management of Anxiety Disorders. Canadian Journal of Psychiatry.
Medical Council of Canada. (2024). MCCQE Part I Clinical Decision-Making and Multiple-Choice Question Objectives.