ICD-116B20	OBSESSIVE-COMPULSIVE DISORDER (OCD) Obsessive-compulsive disorder
ICD-10F42	Obsessive-compulsive disorder
DSM-5-TRF42.2	Obsessive-Compulsive Disorder

1. Definition and nosology

Obsessive-Compulsive Disorder (OCD; ICD-11: 6B20; DSM-5-TR: F42.2) — a disorder characterized by recurrent, ego-dystonic obsessions (unwanted, intrusive thoughts, images, impulses) or compulsions (repetitive behaviors or mental acts). Usually both are present. The patient performs the compulsion to reduce anxiety or prevent a feared outcome.

DSM-5 (2013) — OCD removed from anxiety disorders distinct Moved to the “Obsessive-Compulsive and Related Disorders” category; ICD-11 parallel step.

2. History

• Esquirol J.E.D. (1838) — “monomanie raisonnante”.
• Janet P. (1903) — ‘psychasthénie’.
• Freud (1909) — “Rat Man” case.
• Skinner B.F. and Mowrer O.H. (1947) — two-factor learning theory (classical conditioning + operant avoidance); basis of ERP.
• Meyer V. (1966) — first clinical application of Exposure and Response Prevention (ERP).
• DSM-5 (2013) and ICD-11 (2019) — OCD separated from anxiety disorders.

3. Epidemiology

• Lifetime prevalence: 1.6–2.3% (Ruscio A.M. et al. Mol Psychiatry 2010).
• Gender: approximately equal; relatively more common in women in adulthood, early onset in childhood in men.
• Onset: bimodal — prepubertal (10–12 years, males) and early adulthood (20–25 years).
• Comorbidity: MDD ~60%, anxiety disorders, tic disorders, autism, hoarding, BDD.

4. Aetiology and pathogenesis

• Heritability 40–50% (Mataix-Cols D. et al. JAMA Psychiatry 2013).
• Neurobiological — hyperactivity of the cortico-striato-thalamo-cortical (CSTC) circuit (orbitofrontal, cingulate, caudate); serotonergic dysregulation (SSRI effect); glutamatergic dysregulation.
• Genetic research — SLC1A1 (glutamate transporter), serotonin genes.
• PANDAS — rare onset of OCD following streptococcal infection (NIMH 2017).
• Trauma, stress triggering factors.

5. Clinical features

Typical symptom domains

• Contamination / cleanliness — most frequent; hand washing, disinfection compulsions.
• Doubting / checking — lock, plate, electrical devices.
• Symmetry / precision / ‘just right’ — related to orderliness.
• Aggressive / sexual / religious obsessions — ego-dystonic, causing distress.
• Hoarding — Separate category in ICD-11 (6B24).

Ego-dystonia

The patient accepts that obsessions are their own thoughts, but unwanted, irrational, or unacceptable (insight varies — DSM-5-TR insight qualifiers: good / poor / absent).

6. Diagnosis

6.1 Unified diagnostic criteria

A. Presence of obsession, compulsion, or both.

• Obsessions: repeated, persistent, unwanted thoughts/images/impulses; creates distress; patient attempts to suppress or neutralize with other thoughts/actions.
• Compulsions: Repetitive behavior (hand washing, checking, ordering) or mental act (counting, praying) performed as a response to an obsession or according to rigid rules; aimed at reducing anxiety, but either unrealistic or excessive.

B. Obsession/compulsions take >1 hour per day or cause significant distress/functional impairment.

C. Exclusion of substance or medical condition.

D. Not better explained by another mental disorder.

6.2 Source-specific clarifications

• DSM-5-TR — insight specifiers (good/fair — poor — absent/delusional); tic-related subtype.
• ICD-11 — parallel; hoarding (6B24), BDD (6B21), olfactory reference (6B22) separate categories.
• NICE CG31 (2005, 2019 surveillance) — diagnostics via clinical interview + Y-BOCS.

6.3 Diagnostic algorithm

1. Clinical interview.
2. SCID-5, Y-BOCS (Yale-Brown Obsessive Compulsive Scale) — the gold standard severity scale; CY-BOCS for children.
3. OCI-R (Obsessive Compulsive Inventory-Revised) — self-assessment.
4. Comorbidity (depression, anxiety, tic, autism, BDD, hoarding).

6.4 Differential diagnosis

7. Examination and assessment

• Y-BOCS / CY-BOCS — gold standard.
• OCI-R — self-assessment.
• Comorbidity (depression, anxiety).

8. Treatment

8.1 General Principles (NICE CG31 · APA · WFSBP)

1. First-line psychotherapy: ERP (Exposure and Response Prevention) — patient is exposed to feared object/situation and does not perform compulsion. 12–20 sessions. Evidence: Foa E.B. et al. RCTs; effect substantial.
2. First-line pharmacotherapy: SSRIs at high dose — fluoxetine (40–80 mg), sertraline (200 mg), paroxetine (40–60 mg), fluvoxamine (200–300 mg), escitalopram (20–40 mg). In OCD a higher dose than the standard depression dose is required; effect 8–12 weeks (slower than in depression).
3. Combination CBT/ERP + SSRI — superior to monotherapy in moderate-to-severe OCD (Foa E.B. et al. Am J Psychiatry 2005).
4. Clomipramine (TCA) — first-line alternative; in case of non-response to SSRI; anticholinergic and cardiac side effects.
5. Augmentation (SSRI + low-dose atypical antipsychotic) — risperidone, aripiprazole; in refractory cases.
6. Refractory severe OCD: Deep Brain Stimulation (DBS — ventral capsule/ventral striatum), neurosurgery (capsulotomy, cingulotomy); ECT ineffective; ketamine/esketamine rapid effect studies ongoing.
7. Duration of treatment — long-term; ≥ 1–2 years after remission, lifelong in case of multiple relapses.

8.2 Source-specific clarifications

• NICE CG31 (2005, 2019 surveillance) — stepped approach by severity; ERP first-line; SSRIs for moderate-severe.
• APA Practice Guideline for OCD (2007) — same; clomipramine strong based on evidence, but second-line due to side effects.
• WFSBP (Bandelow B. et al. 2008) — SSRI dose ranges and titration.
• NICE CG31 PANDAS — routine antibiotic prophylaxis not recommended.

Treatment methods

1. Exposure and Response Prevention (ERP) — Meyer (Meyer V.), Foa (Foa E.B.) — The patient is exposed to feared object (e.g., “dirty” object) and does not perform compulsion (washing hands); anxiety gradually decreases (habituation). Standard course 12–20 sessions, 1–2 times per week; more intensive format (daily) is effective. Evidence: Foa E.B. et al. Am J Psychiatry 2005.
2. CBT — cognitive component — Addition to ERP; re-evaluation of thoughts about obsession; targets “thought-action fusion” (TAF) and hyper-responsibility cognitions.
3. Yale-Brown Obsessive-Compulsive Scale (Y-BOCS — Yale-Brown Obsessive Compulsive Scale) — Goodman (Goodman W.K.) — 10 items; 5 obsessions + 5 compulsions; gold standard; CY-BOCS in children.
4. SSRI High Dose — In OCD significantly higher dose than standard depression dose is required; titration over 8–12 weeks; in case of non-response dose is increased to maximum.
5. Clomipramine (TCA) — Evidence in OCD strong (CMI multicenter trial 1991); cardiac and anticholinergic side effects; second-line.
6. Deep Brain Stimulation (DBS) — Surgical intervention for refractory severe OCD; target ventral capsule/ventral striatum. Greenberg B.D. et al. Mol Psychiatry 2010.

9. Prognosis

• Chronic course, but significant improvement with adequate treatment.
• Comorbid depression, tics and autism are markers of poor prognosis.
• Early onset and poor insight — more difficult treatment.

10. Myths and misconceptions

Myth 1: “OCD is just a personality trait related to cleanliness and orderliness”

Evidence: Clinical OCD is ego-dystonic, causes distress and functional impairment; obsessive-compulsive personality disorder (OCPD) is ego-syntonic distinct disorder. Clinical diagnosis based on Y-BOCS severity and duration.

Myth 2: “The patient can ‘voluntarily stop’ obsessions”

Evidence: OCD is dysregulation of CSTC circuit; not voluntarily controlled; ERP and SSRIs affect it at a neurobiological level.

Myth 3: “SSRIs work in OCD at depression doses”

Evidence: In OCD, SSRIs require high doses (fluoxetine 60–80 mg, sertraline 200 mg); depression dose (e.g., fluoxetine 20 mg) often does not respond.

Myth 4: “ERP causes trauma because it keeps the patient in a feared situation”

Evidence: ERP is structured, stepwise, and conducted with patient consent; demonstrates long-term proven efficacy.

Myth 5: “PANDAS is the main cause of OCD, everyone should take antibiotics”

Evidence: NIMH 2017 — PANDAS is a rare event; routine antistreptolysin O tests and antibiotic prophylaxis are not recommended; only if a classic clinical picture is present.

Myth 6: “Allowing compulsions to be performed calms symptoms”

Evidence: Permission (accommodation) for compulsions strengthens OCD; reducing family accommodation is a crucial treatment component.

Myth 7: “Herbal preparations (St John's Wort, kava, omega-3) cure OCD”

Evidence: none have proven efficacy for OCD; St John's Wort carries risk of interaction with SSRIs.

11. Sources

1. WHO. ICD-11. 6B20 Obsessive-compulsive disorder. 2024.
2. APA. DSM-5-TR. 2022.
3. NICE CG31. Obsessive-compulsive disorder and body dysmorphic disorder. 2005, 2019 surveillance.
4. APA. Practice Guideline for the Treatment of Patients with Obsessive-Compulsive Disorder. 2007.
5. Bandelow B. et al. WFSBP guidelines for the pharmacological treatment of anxiety, obsessive-compulsive and post-traumatic stress disorders. World J Biol Psychiatry 2008;9(4):248–312.
6. Foa E.B., Liebowitz M.R., Kozak M.J. et al. Randomized, placebo-controlled trial of exposure and ritual prevention, clomipramine, and their combination in the treatment of obsessive-compulsive disorder. Am J Psychiatry 2005;162(1):151–161.
7. Ruscio A.M., Stein D.J., Chiu W.T., Kessler R.C. The epidemiology of obsessive-compulsive disorder in the National Comorbidity Survey Replication. Mol Psychiatry 2010;15(1):53–63.
8. Mataix-Cols D. et al. Familial risks of obsessive-compulsive disorder. JAMA Psychiatry 2013;70(7):709–717.
9. Greenberg B.D. et al. Deep brain stimulation of the ventral internal capsule/ventral striatum for obsessive-compulsive disorder. Mol Psychiatry 2010;15(1):64–79.
10. NIMH. PANDAS/PANS Information for Clinicians. 2017.
11. Goodman W.K., Price L.H., Rasmussen S.A. et al. The Yale-Brown Obsessive Compulsive Scale. I. Development, use, and reliability. Arch Gen Psychiatry 1989;46(11):1006–1011.