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# Obsessive-compulsive disorder (OCD)

OCD causes unwanted, repeated thoughts (obsessions) and urges to perform rituals (compulsions) that take time and disrupt daily life.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Caudate nucleus](https://durgical.com/en/anatomy/caudate-nucleus/)
- [Cingulate gyrus](https://durgical.com/en/anatomy/cingulate-gyrus/)
- [Frontal lobe](https://durgical.com/en/anatomy/superior-frontal-gyrus/)
- [Thalamus](https://durgical.com/en/anatomy/thalamus/)
- [Putamen](https://durgical.com/en/anatomy/putamen/)
- [Globus pallidus](https://durgical.com/en/anatomy/globus-pallidus/)

## Why it happens

- [Basal ganglia and movement control](https://durgical.com/en/physiology/basal-ganglia-and-movement-control/)

## What it is

A chronic mental disorder defined by obsessions (intrusive, unwanted thoughts, images or urges that cause anxiety) and/or compulsions (repetitive acts or mental rituals done to reduce that anxiety). The person usually recognises them as excessive, and they take up time or cause real distress.

## Who gets it

Affects roughly 1–3% of people over a lifetime worldwide, with similar figures reported in Latin America. It usually begins in adolescence or early adulthood; boys tend to start earlier. Diagnosis is often delayed for years because people hide their symptoms.

## Causes

- Genetic predisposition: higher risk in first-degree relatives
- Dysfunction of the cortico-striato-thalamo-cortical circuit (orbitofrontal cortex, anterior cingulate, caudate)
- Altered serotonin (and glutamate, dopamine) signalling
- In some children, sudden onset after streptococcal infection (PANDAS, debated)

## Risk factors

- Family history of OCD or tic disorders
- Childhood trauma or highly stressful life events
- Tourette syndrome or other tic disorders
- Pregnancy and the postpartum period (new onset or worsening)

## Pathophysiology

Imaging studies show overactivity in a loop linking the orbitofrontal cortex, anterior [cingulate gyrus](https://durgical.com/en/anatomy/cingulate-gyrus/), [caudate nucleus](https://durgical.com/en/anatomy/caudate-nucleus/) and [thalamus](https://durgical.com/en/anatomy/thalamus/). This loop normally flags a worry and then lets it go; in OCD the 'something is wrong' signal persists, and the compulsion brings only brief relief, which reinforces it. Good response to serotonergic drugs supports a role for serotonin.

## Classification

- Insight specifier: good or fair, poor, or absent insight/delusional beliefs
- Tic-related OCD
- Related disorders: body dysmorphic disorder, hoarding disorder, trichotillomania, excoriation ([skin](https://durgical.com/en/anatomy/skin/) -picking) disorder

## Symptoms and signs

- Contamination fears with excessive washing or cleaning
- Doubts with repeated checking (locks, stove, mistakes)
- Need for symmetry, order or exactness; arranging and counting
- Unwanted aggressive, sexual or religious thoughts, with mental rituals or reassurance seeking
- Rituals taking more than an hour a day, avoidance of triggers, and skin damage from washing

## Red flags

- Suicidal thoughts, often linked to coexisting depression
- Inability to eat, sleep or leave home because of rituals
- Sudden onset of OCD symptoms or tics in a child, especially after an infection
- Obsessions about harming a baby in the postpartum period (needs assessment, though usually ego-dystonic and not acted on)

## Diagnosis

**Clinical**
Clinical interview using DSM-5-TR criteria: obsessions and/or compulsions that are time-consuming (over an hour a day) or cause clinically significant distress or impairment, not explained by a substance or another disorder. Severity is often rated with the Y-BOCS scale (CY-BOCS in children).

**Tests**
No laboratory test confirms OCD. Screening for depression, suicide risk and substance use; thyroid tests or infection workup only when the picture suggests them.

**Imaging**
Not needed for diagnosis. Brain imaging is reserved for atypical late onset or neurological signs.

## Differential diagnosis

- Obsessive-compulsive personality disorder (traits are ego-syntonic, no true obsessions)
- Generalised anxiety disorder (real-life worries rather than intrusive, senseless thoughts)
- Psychotic disorders with delusions
- Tic disorders and the restricted, repetitive behaviours of autism
- Depression with ruminations

## Goal of treatment

Reduce the time and distress caused by obsessions and rituals, restore daily functioning, and treat coexisting depression or tics; full remission is possible but many people keep milder symptoms.

## Treatment

**Conservative**
Cognitive behavioural therapy with exposure and response prevention (ERP) is first-line: gradual facing of the feared trigger without performing the ritual.

**Medical**
Selective serotonin reuptake inhibitors (SSRIs) are the first-line drugs, usually at higher doses and for longer trials than in depression; clomipramine is an alternative. Augmentation with low-dose antipsychotics in resistant cases or with tics.

**Procedure**
For severe, treatment-resistant OCD: deep transcranial magnetic stimulation and, in specialised centres, deep brain stimulation or ablative neurosurgery.

**Follow-up**
Follow-up of Y-BOCS scores, suicide risk (especially in adolescents starting SSRIs) and adverse effects.

## Complications

- Major depression and suicide risk
- Loss of school, work and family functioning
- Dermatitis from excessive hand washing
- Substance use as self-treatment

## Prognosis

Usually chronic with waxing and waning symptoms. Most people improve substantially with ERP and/or SSRIs; earlier onset, poor insight, hoarding and comorbidity predict a worse course.

## Test yourself

Think of the answer, then tap the question to see it.

## Which brain circuit is overactive in OCD?

The cortico-striato-thalamo-cortical loop: orbitofrontal cortex, anterior cingulate, caudate nucleus and thalamus.

## What is the first-line psychotherapy for OCD?

Cognitive behavioural therapy with exposure and response prevention (ERP).

## Which drug class is first-line for OCD, and which tricyclic is an alternative?

SSRIs, usually at higher doses than for depression; clomipramine is the tricyclic alternative.

## How does OCD differ from obsessive-compulsive personality disorder?

In OCD the obsessions are ego-dystonic (unwanted, distressing); in OCPD perfectionism and rigidity are ego-syntonic and there are no true obsessions or compulsions.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/conditions/obsessive-compulsive-disorder/)

## Related conditions

- [Personality disorders (clusters A, B and C)](https://durgical.com/en/conditions/personality-disorders/)
- [Autism spectrum disorder (ASD)](https://durgical.com/en/conditions/autism-spectrum-disorder/)
- [Serotonin syndrome](https://durgical.com/en/conditions/serotonin-syndrome/)
- [Attention-deficit/hyperactivity disorder (ADHD)](https://durgical.com/en/conditions/attention-deficit-hyperactivity-disorder/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Obsessive-Compulsive Disorder](https://medlineplus.gov/obsessivecompulsivedisorder.html) (MedlinePlus, US National Library of Medicine, 2026).

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Source: https://durgical.com/en/conditions/obsessive-compulsive-disorder/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/obsessive-compulsive-disorder/