OCD

What is OCD?

A chronic psychiatric disorder with recurrent obsessions (intrusive, ego-dystonic thoughts/images/urges) and/or compulsions (repetitive behaviours to neutralise anxiety), time-consuming >1 hr/day, causing significant distress or functional impairment.

What does ego-dystonic mean in OCD?

The patient recognises their thoughts as irrational/excessive but cannot stop them. Insight is usually preserved — this distinguishes OCD from psychosis.

What is a compulsion?

A repetitive behaviour or mental act performed to reduce the anxiety caused by an obsession. Compulsions are negatively reinforced — they provide short-term relief, creating a habit loop.

What is the lifetime prevalence of OCD?

~2-3%. Bimodal onset: early (10-12 yrs) and late adolescence/early adulthood (~20-25 yrs). Males have earlier onset (often with tics); females have slightly higher overall adult prevalence.

What are the 4 OCD symptom dimensions?

1. Contamination / Washing 2. Symmetry / Ordering 3. Forbidden Thoughts / Checking 4. Hoarding

Name 5 common types of compulsions.

1. Washing/Cleaning rituals 2. Checking (locks, stove) 3. Counting/Repeating a fixed number of times 4. Ordering/Arranging until 'feels right' 5. Mental compulsions (silent praying, neutralising bad thoughts)

What are the 3 DSM-5 insight specifiers for OCD?

Good/fair insight: recognises beliefs are probably not true. Poor insight: thinks beliefs are probably true. Absent insight/delusional: completely convinced. WARNING: Absent insight does NOT mean psychosis.

What neurotransmitter is most implicated in OCD, and what is the evidence?

Serotonin — strongest evidence: SSRIs and clomipramine (potent serotonin reuptake inhibitors) are effective; weak/non-serotonergic antidepressants are not. Also implicated: Dopamine (tic-related OCD) and Glutamate (CSTC circuit).

Explain the CSTC circuit in OCD.

Cortico-Striato-Thalamo-Cortical circuit hyperactivity. Normally: OFC/ACC send 'something is wrong' signal; caudate filters unnecessary worry before reaching thalamus/cortex. In OCD: this gating FAILS; loop keeps re-firing; anxiety signal never switches off. This is WHY checking/reassurance doesn't help — the loop resets, not the worry.

What are the genetic findings in OCD?

MZ twin concordance ~0.65 vs DZ ~0.15. First-degree relatives have 4-8x increased risk. Associated with SLC1A1 (glutamate transporter gene) — recent research focus.

What is PANDAS?

Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections. Abrupt-onset OCD in children following strep infection — autoantibodies cross-react with basal ganglia. Needs paediatric/immunology referral.

What does Mowrer's two-factor theory say about OCD?

Factor 1 (Classical conditioning): Neutral stimulus becomes associated with fear. Factor 2 (Operant conditioning): Compulsion is negatively reinforced by anxiety relief. This is the behavioural basis for ERP therapy.

What are the DSM-5-TR criteria for OCD? (mnemonic)

Mnemonic: TIME. T = Time-consuming (>1 hr/day). I = Intrusive thoughts/images/urges. M = Marked distress or impairment. E = Ego-dystonic. Also: not due to substances/medical condition; not better explained by another mental disorder.

How does DSM-5 classify OCD vs prior classification?

OCD was MOVED OUT of anxiety disorders in DSM-5 — now in its own chapter: 'Obsessive-Compulsive and Related Disorders'. Both DSM-5 and ICD-11 agree OCD is NOT an anxiety disorder — it has its own CSTC circuit-based neurobiological identity.

How do you distinguish OCD from GAD?

GAD: Worries about real-life concerns (finances, health, relationships) — realistic, not senseless. OCD: Obsessions are intrusive, senseless, ego-dystonic — the person recognises them as irrational.

How do you distinguish OCD from psychosis?

OCD: Obsessions are ego-dystonic with PRESERVED INSIGHT — patient knows thoughts are irrational. Psychosis: Delusions = fixed false beliefs with NO insight. WARNING: OCD with absent insight does NOT equal psychosis — don't give antipsychotic monotherapy.

How do you distinguish OCD from Autism Spectrum Disorder?

OCD rituals are ego-DYSTONIC — distressing, unwanted by the patient. ASD rituals are ego-SYNTONIC — comforting, desired by the patient.

What is the gold standard rating scale for OCD severity?

Y-BOCS (Yale-Brown Obsessive Compulsive Scale). Used for severity assessment and monitoring treatment response. Neuroimaging (fMRI/PET) shows CSTC hyperactivity but is a research tool only — not routine clinical use.

What is first-line treatment for OCD?

Pharmacotherapy: SSRI at HIGH dose (Fluoxetine, Fluvoxamine, Sertraline, Paroxetine, Escitalopram). Psychotherapy: CBT with ERP (Exposure and Response Prevention). Combined SSRI + CBT = best outcome, especially in severe cases. KEY: OCD needs higher doses and longer duration (10-12 weeks) than depression.

What is ERP and why does it work?

Exposure and Response Prevention. Exposure: Gradual, planned exposure to feared stimulus (e.g. touching 'contaminated' object). Response Prevention: Not performing the compulsion (e.g. not washing hands after). Rationale: Anxiety naturally decreases over time with prolonged exposure (habituation) — breaks the negative reinforcement cycle.

What is second-line pharmacotherapy for OCD?

Clomipramine (TCA — potent serotonergic agent). Effective but more side effects: anticholinergic effects, cardiotoxicity in overdose. Used when SSRIs fail.

How is treatment-resistant OCD managed?

1. Augment SSRI with low-dose atypical antipsychotic (Risperidone, Aripiprazole) — especially if poor insight or comorbid tics. 2. Switch to Clomipramine. 3. rTMS (repetitive Transcranial Magnetic Stimulation) — FDA approved, targets SMA/OFC. 4. Deep Brain Stimulation (DBS) — targets anterior limb of internal capsule / nucleus accumbens.

What is the role of the family in OCD management?

Family must NOT participate in rituals or provide reassurance — this is called 'family accommodation' and it WORSENS OCD. Family psychoeducation is essential.

What are good prognostic factors in OCD?

Later age of onset. Good insight. Short duration before treatment. Good initial treatment response. Mild symptoms, good premorbid functioning.

What are poor prognostic factors in OCD?

Early/childhood onset. Poor insight or delusional beliefs. Hoarding symptoms (most resistant to treatment). Comorbid tic disorder / Tourette's. Comorbid personality disorder. Long duration of untreated illness. Course: Often chronic, waxing/waning.

What are the recent advances in OCD treatment?

Glutamate hypothesis: new targets — Memantine, N-acetylcysteine (under research). Ketamine: rapid but short-lived anti-obsessional effect (under research). rTMS: now FDA-approved for resistant OCD. DBS: established for severe refractory OCD. SLC1A1 gene / GWAS studies ongoing. PANDAS/PANS: growing recognition of autoimmune OCD in children.