Gangguan Obsesif-Kompulsif

01Pathophysiology

OCD arises from dysfunction within the cortico-striato-thalamo-cortical (CSTC) loop, a neural circuit connecting the orbitofrontal cortex, caudate nucleus, globus pallidus, and thalamus. Under normal conditions, this circuit modulates behavioral responses to internal and external stimuli. In OCD, the circuit becomes hyperactive, creating a "stuck switch" phenomenon: the brain continually signals that something is wrong or incomplete, even when no real threat exists.

The neurotransmitter most strongly implicated is serotonin (5-HT). Reduced serotonergic transmission in the CSTC pathway leads to a failure of inhibitory control over intrusive thoughts. This explains why SSRIs, which increase synaptic serotonin availability, are the pharmacological cornerstone of treatment. Dopaminergic pathways also play a secondary role, which is why dopamine-blocking agents (low-dose antipsychotics) can augment treatment in refractory cases.

The obsessions are experienced as ego-dystonic, meaning the patient recognizes them as irrational products of their own mind but cannot suppress them. This is a critical distinction from psychotic disorders, where intrusive thoughts are ego-syntonic or attributed to external forces. The distress generated by obsessions drives the patient to perform compulsions, which are repetitive behaviors intended to neutralize the anxiety. However, these compulsions provide only temporary relief and reinforce the obsessive cycle, creating a self-perpetuating loop.

The PPDGJ-III emphasizes a strong bidirectional relationship between OCD and depression. Obsessive symptoms and depressive symptoms frequently coexist and tend to fluctuate in parallel. This overlap is clinically important because it affects both diagnosis and treatment sequencing.

02Classification and Clinical Manifestation

The PPDGJ-III classifies OCD into subtypes based on which component predominates:

Per the PPDGJ-III, the distinction between subtypes matters because compulsive actions respond better to behavioral therapy, while obsessive thoughts tend to require pharmacological intervention. Most patients in clinical practice present with the mixed subtype.

03Diagnostic Workup

OCD is a clinical diagnosis. There is no laboratory test or imaging study that confirms it. The diagnosis rests entirely on meeting the PPDGJ-III criteria through a structured clinical interview.

The PPDGJ-III requires the following elements to be established:

First, the obsessive or compulsive symptoms (or both) must be present almost every day for at least two consecutive weeks. This time criterion is important on exams because it differentiates OCD from transient intrusive thoughts that most people experience.

Second, four hallmark features of obsessions must be confirmed: (a) the patient recognizes the thoughts as their own (not inserted from outside), (b) there is at least one thought or act that the patient tries but fails to resist, (c) performing the compulsion is not inherently pleasurable (relief from anxiety alone does not count as pleasure), and (d) the thoughts or impulses are unpleasantly repetitive.

Third, the clinician must carefully evaluate comorbid depression. The PPDGJ-III provides a clear diagnostic hierarchy: if an acute episode occurs with both OCD and depressive symptoms, prioritize whichever symptoms appeared first. If OCD symptoms are present without concurrent depressive disorder, diagnose OCD. If both are present and neither predominates, depression takes diagnostic priority. For chronic courses, prioritize the symptom cluster that persists when the other is fading.

Fourth, obsessive symptoms occurring in the context of schizophrenia, Tourette syndrome, or organic mental disorders should be classified as part of those primary conditions, not as independent OCD.

The Y-BOCS is the standard tool for quantifying severity. It assesses five dimensions of obsessions and five dimensions of compulsions (time occupied, interference, distress, resistance, control), each scored 0-4, yielding a total score of 0-40.

04Management and Treatment

Acute management begins with establishing the diagnosis and assessing severity using the Y-BOCS. For mild cases (Y-BOCS less than 16), CBT with ERP alone may be sufficient. For moderate-to-severe cases, an SSRI should be started concurrently with psychotherapy referral.

The key pharmacological principle in OCD is that SSRIs must be dosed higher and tried longer than in depression. While depression may respond to fluoxetine 20 mg within 4-6 weeks, OCD typically requires 40-80 mg for 8-12 weeks before improvement is seen. This is a frequently tested concept. If a patient has been on fluoxetine 20 mg for 4 weeks with no improvement, the next best step is to increase the dose, not switch medications.

If two adequate SSRI trials fail, clomipramine (a tricyclic antidepressant with potent serotonin reuptake inhibition) is the next option. It is the most effective single agent for OCD but is positioned as second-line because of its side effect profile: anticholinergic effects (dry mouth, constipation, urinary retention), weight gain, sedation, orthostatic hypotension, and risk of QT prolongation and seizures at higher doses.

For patients who show partial response to SSRIs, augmentation with a low-dose atypical antipsychotic (risperidone or aripiprazole) is preferred over switching. This strategy leverages the dopaminergic contribution to OCD pathophysiology.

CBT with Exposure and Response Prevention (ERP) is the most evidence-supported psychotherapy. In ERP, the patient is systematically exposed to obsession-triggering stimuli (e.g., touching a "contaminated" surface) and then prevented from performing the compulsive ritual (e.g., handwashing). Over repeated sessions, habituation occurs and the obsessive-compulsive cycle weakens. The PPDGJ-III notes that compulsive actions are particularly responsive to behavioral therapy, supporting ERP as the preferred modality when rituals predominate.

Long-term management involves continuing the effective SSRI for at least 1-2 years after symptom control is achieved. Discontinuation should be gradual (taper over 1-2 months) and accompanied by ongoing CBT to prevent relapse. Relapse rates are high (up to 50%) when medication is stopped without concurrent psychotherapy.

Contraindications and cautions:

• Clomipramine is contraindicated with MAOIs (risk of serotonin syndrome) and in patients with cardiac conduction abnormalities.

• SSRIs in pregnancy: sertraline and fluoxetine are generally considered safer options, but paroxetine is avoided due to cardiac teratogenicity.

• In pediatric OCD, CBT alone is first-line for mild cases. If pharmacotherapy is needed, only SSRIs with pediatric approval (fluoxetine, fluvoxamine, sertraline) should be used, with careful monitoring for suicidality.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students lose points on OCD questions involves the OCD-depression diagnostic hierarchy outlined in the PPDGJ-III. When a vignette presents a patient with both obsessive-compulsive and depressive symptoms, students instinctively reach for OCD as the diagnosis because the rituals are dramatic and memorable. However, the PPDGJ-III explicitly states that when both symptom clusters are present and equally prominent, depression takes diagnostic priority. The correct answer in that scenario is depressive disorder, not OCD. The only time OCD is diagnosed in the presence of depression is when the obsessive-compulsive symptoms clearly appeared first or persist while depressive symptoms remit.

A second common trap involves ego-dystonicity. Students sometimes confuse OCD with OCPD because both involve orderliness and perfectionism. The critical distinction is insight: the OCD patient is distressed by their thoughts and wishes they could stop, while the OCPD patient views their behavior as reasonable and desirable. If a vignette describes someone who is proud of their meticulousness and sees nothing wrong with rechecking their work five times, that is OCPD, not OCD.

A third pitfall involves treatment dosing. Students may select "start fluoxetine 20 mg" as first-line management for OCD. While fluoxetine is correct, 20 mg is a subtherapeutic dose for OCD. The tested principle is that OCD requires higher SSRI doses and longer treatment trials than depression. Similarly, declaring treatment failure before completing a full 8-12 week trial at an adequate dose is a commonly tested error.

Finally, watch for the "secondary obsessions" trap. If a vignette describes obsessive-compulsive symptoms in a patient with established schizophrenia, Tourette syndrome, or an organic brain disorder, the PPDGJ-III instructs you to attribute those symptoms to the primary condition. The answer is never a separate OCD diagnosis in that context.

The core competency being tested across all OCD questions is the ability to recognize ego-dystonic intrusive thoughts, apply the correct diagnostic hierarchy when comorbidities exist, and sequence treatment appropriately with attention to dosing and duration.