Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is characterized by obsessions - recurrent, intrusive, unwanted thoughts, images, or urges that cause marked anxiety - and compulsions - repetitive behaviors or mental acts performed to reduce that anxiety or to prevent a feared event. The behaviors are typically recognized as excessive or unreasonable yet feel difficult to resist, and they consume time and impair functioning. In DSM-5 OCD heads a distinct chapter of obsessive-compulsive and related disorders, set apart from the anxiety disorders.

Definition

Obsessive-compulsive disorder is a condition defined by the presence of obsessions, compulsions, or both, that are time-consuming or cause clinically significant distress or impairment, where obsessions are recurrent intrusive thoughts, urges, or images and compulsions are repetitive behaviors or mental acts the person feels driven to perform in response to an obsession or rigid rules.

Scope

This entry covers the clinical features of obsessions and compulsions, the cortico-striato-thalamo-cortical circuitry and learning processes implicated in OCD, its epidemiology and common symptom dimensions, and the evidence base for treatment. It is reference-educational and does not provide individual diagnostic or treatment guidance.

Core questions

• How do obsessions and compulsions relate to one another functionally?
• Why are compulsions so resistant to change despite being recognized as excessive?
• What brain circuits and learning processes are implicated in OCD?
• What treatments have the strongest evidence in OCD?

Key concepts

• Obsessions
• Compulsions and rituals
• Exposure and response prevention
• Inflated responsibility and threat appraisal
• Cortico-striato-thalamo-cortical circuitry
• Symptom dimensions (contamination, harm, symmetry, taboo thoughts)

Key theories

Negative reinforcement of compulsions

Learning accounts hold that compulsions are maintained because they temporarily reduce the distress evoked by obsessions; this immediate relief negatively reinforces the ritual while preventing the person from learning that the feared outcome does not occur, providing the rationale for exposure and response prevention.

Mechanisms

OCD is associated with dysfunction in cortico-striato-thalamo-cortical circuits, including the orbitofrontal cortex, anterior cingulate, and striatum, and with serotonergic involvement reflected in the disorder's response to serotonin reuptake inhibitors. Cognitive-behavioral accounts emphasize maladaptive appraisals of intrusive thoughts - such as inflated responsibility and overestimation of threat - and the negative reinforcement of compulsions, which relieve distress momentarily while preventing corrective learning. Symptoms cluster into recognizable dimensions such as contamination/washing, harm/checking, and symmetry/ordering.

Clinical relevance

OCD is often chronic and can be severely disabling, and it is frequently underrecognized because affected individuals may conceal symptoms. This entry describes how the disorder is defined and studied to support understanding and evidence appraisal; it is not a basis for diagnosing or treating an individual.

Epidemiology

OCD has a lifetime prevalence on the order of a few percent of the population, with onset commonly in childhood, adolescence, or early adulthood, a roughly equal sex distribution overall, and frequent comorbidity with depression, other anxiety disorders, and tic disorders. The course is often chronic and fluctuating.

Evidence & guidelines

Cognitive behavioral therapy centred on exposure and response prevention, and serotonergic medication (SSRIs and clomipramine), are the best-supported treatments, with meta-analytic evidence for CBT in OCD and related disorders. DSM-5-TR places OCD in the obsessive-compulsive and related disorders chapter, and ICD-11 codes it 6B20; this entry summarizes the evidence base rather than recommending a regimen.

History

Obsessive-compulsive phenomena have been described for centuries and were long classified among the neuroses and, in DSM-III and DSM-IV, among the anxiety disorders. Behavioral work in the 1960s-1980s established exposure and response prevention as an effective treatment, and Foa and Kozak's emotional-processing theory provided a mechanistic framework. DSM-5 (2013) reclassified OCD into a dedicated chapter of obsessive-compulsive and related disorders.

Debates

Should OCD be classified as an anxiety disorder or in its own category?

DSM-5 moved OCD out of the anxiety disorders into a separate chapter on grounds of distinct neurocircuitry and relations to disorders such as body dysmorphic and hoarding disorder, but its prominent anxiety component and shared treatments keep the placement debated.

Key figures

• Edna Foa
• Dan J. Stein
• Jonathan Abramowitz
• Paul Salkovskis

Seminal works

• foa-kozak-1986
• abramowitz-2009
• stein-2019

Frequently asked questions

What is the difference between an obsession and a compulsion?

An obsession is a recurrent, intrusive, unwanted thought, image, or urge that causes anxiety; a compulsion is a repetitive behavior or mental act performed to reduce that anxiety or prevent a feared outcome. In OCD they typically occur together, with compulsions aimed at neutralizing obsessions.

Why is OCD no longer grouped with the anxiety disorders in DSM-5?

DSM-5 placed OCD in a separate chapter of obsessive-compulsive and related disorders, citing distinct brain circuitry and links to conditions such as body dysmorphic and hoarding disorder, although OCD still shares features and treatments with the anxiety disorders. This entry presents the classification without advising on individual care.