Write a short note on obsessive-compulsive disorder.

Definition

OCD is a chronic disorder characterised by obsessions and/or compulsions that are time-consuming (conventionally more than 1 hour per day) or cause marked distress and functional impairment. Lifetime prevalence is 2–3%, with onset typically in adolescence or early adulthood; earlier onset is commoner in males.

Obsessions are recurrent, intrusive, unwanted thoughts, images or impulses that are recognised by the patient as their own (unlike thought insertion in schizophrenia), are resisted, and cause anxiety. Common themes: contamination, doubt, symmetry, aggressive or blasphemous thoughts.

Compulsions are repetitive behaviours or mental acts performed to reduce the anxiety generated by obsessions — washing, checking, counting, ordering, repeating, seeking reassurance. Relief is temporary, which reinforces the cycle.

Key Diagnostic Features

• The thoughts are ego-dystonic — unwanted and inconsistent with the patient's own values, which is why they cause distress.
• Insight is usually preserved — patients know the thoughts are irrational, which distinguishes OCD from delusional disorder. Insight may be poor in a minority.
• Attempts at resistance cause rising anxiety; performing the compulsion relieves it.

Aetiology

• Neuroanatomical: hyperactivity of the cortico-striato-thalamo-cortical circuit, particularly the orbitofrontal cortex, anterior cingulate and caudate nucleus.
• Neurochemical: serotonergic dysfunction — supported by the specific response to serotonergic drugs.
• Genetic: higher concordance in monozygotic twins; increased family risk.
• Post-infectious: PANDAS — paediatric autoimmune neuropsychiatric disorder associated with group A streptococcal infection, causing abrupt-onset OCD and tics in children.
• Associations: Tourette syndrome, Sydenham's chorea, head injury, and the postpartum period.

Assessment

Severity is measured with the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), which rates time occupied, interference, distress, resistance and control for both obsessions and compulsions. Screen for comorbid depression (present in up to two-thirds), anxiety disorders and tics.

Differential Diagnosis

Management

• Cognitive behavioural therapy with exposure and response prevention (ERP) — the psychological treatment of choice and first-line for mild to moderate disease. The patient is exposed to the feared stimulus while being prevented from performing the ritual, allowing anxiety to extinguish naturally.
• SSRIs — first-line pharmacotherapy. OCD characteristically requires higher doses and a longer trial (10–12 weeks) than depression, a point examiners often test.
• Clomipramine — the most effective tricyclic, reserved for SSRI failure because of anticholinergic and cardiac effects.
• Augmentation with a low-dose atypical antipsychotic (risperidone, aripiprazole) for partial response, particularly with comorbid tics.
• Deep brain stimulation or stereotactic surgery (cingulotomy, capsulotomy) — reserved for severe, refractory, disabling disease.
• Treat comorbid depression; involve family, discouraging their participation in reassurance rituals, which perpetuates the disorder.

Prognosis

Typically chronic with a fluctuating course; symptoms worsen with stress. With adequate treatment, most achieve substantial improvement, though complete remission is less common. Poor prognostic factors: early onset, poor insight, comorbid tics, and hoarding symptoms.