Obsessive–compulsive disorder (OCD) is a mental health condition characterized by unwanted, intrusive thoughts (obsessions) and repetitive behaviors or mental acts (compulsions) performed to reduce the distress those thoughts cause. The obsessions are often experienced as intrusive and senseless, and compulsions provide only temporary relief but can become time-consuming and disruptive. OCD varies in severity: for some people symptoms are mild and manageable, while for others they significantly interfere with daily life, work, schooling and relationships. For basic information and guidance, see further resources.

Core features and common presentations

Two defining components of OCD are obsessions and compulsions. Obsessions are persistent ideas, impulses or images that recur and are distressing. Compulsions are actions—either visible behaviors or covert mental rituals—performed to neutralize or prevent the feared outcome. Common themes include:

  • Contamination and excessive washing or avoidance.
  • Checking (doors, appliances, locks) driven by fear of harm or mistake.
  • Symmetry, ordering and arranging to feel "just right."
  • Intrusive aggressive, sexual or blasphemous thoughts that are ego-dystonic.
  • Counting, repeating, or mental rituals.

Course, onset and associated features

OCD can begin in childhood, adolescence or adulthood. Many people first notice symptoms in late childhood to early adulthood. Co-occurring conditions are common, especially anxiety disorders, depressive disorders and tic disorders. The disorder often follows a fluctuating course: symptoms may wax and wane and can worsen during times of stress. Clinically significant OCD typically consumes substantial time (for example, an hour or more each day), causes marked distress, and impairs functioning.

Causes and biological perspectives

There is no single cause of OCD; a combination of genetic, neurobiological and environmental factors contributes to risk. Research implicates circuitry connecting frontal cortex and basal ganglia structures as well as neurotransmitter systems such as serotonin. Life events, infections in a minority of childhood-onset cases, and learned behavioral responses to intrusive thoughts can also play roles. For an introduction to evidence-based explanations, consult trusted clinical summaries.

Assessment and treatment

Accurate diagnosis typically involves a clinical interview that distinguishes OCD from normal worry, from obsessive–compulsive personality traits, and from related disorders. Effective treatments are available and commonly include psychological and pharmacological approaches. The most established psychotherapy is cognitive behavioral therapy (CBT) with exposure and response prevention (ERP), which gradually and safely exposes individuals to feared stimuli while preventing the ritualized response. Medications that affect serotonin—selective serotonin reuptake inhibitors (SSRIs)—are often helpful, sometimes at higher doses and for longer periods than used for other conditions. In severe, treatment-resistant cases, augmentation strategies and neuromodulation or surgical options may be considered in specialized settings. More detailed guidance can be found at professional treatment resources.

Social impact and distinctions

OCD can profoundly affect relationships, education and employment when symptoms are persistent and untreated. It is distinct from obsessive–compulsive personality disorder (OCPD): OCD involves unwanted intrusive thoughts and behaviors the person seeks to resist, whereas OCPD reflects enduring personality traits that are ego-syntonic. Many people experience mild obsessive or ritual behaviors at times without meeting criteria for the disorder; diagnosis depends on the level of distress and impairment. For information aimed at people supporting someone with OCD, see support and advocacy resources.

In sum, OCD is a treatable but potentially chronic condition. Early recognition, evidence-based therapy, appropriate medication when indicated, and family or workplace support improve outcomes. Ongoing research continues to refine understanding of its causes and to develop new interventions.