What is obsessive-compulsive disorder?

Obsessive-compulsive disorder (OCD), one of the anxiety disorders, is a potentially disabling illness that traps people in endless cycles of repetitive thoughts and behaviors. People with OCD are plagued by recurring and distressing thoughts, fears, or images (obsessions) they cannot control. The anxiety (nervousness) produced by these thoughts leads to an urgent need to perform certain repetitive behaviors, rituals, or routines (compulsions). The compulsions are performed in an attempt to prevent the obsessive thoughts or make them go away; not performing the rituals increases the anxiety.

Performing the compulsions may lessen or relieve the anxiety temporarily; however, the person is “compelled” to perform the behaviors again when the obsessions return. This OCD cycle may progress to the point of taking up hours of the person’s day and significantly interfering with normal activities. People with OCD are often aware that their obsessions and compulsions are senseless or unrealistic, but they cannot stop themselves.

How common is obsessive-compulsive disorder?

OCD afflicts about 2.2 million adults in the United States. The disorder usually first appears in childhood, adolescence or early adulthood. It occurs about equally in men and women, and affects people of all races and socioeconomic backgrounds.

What causes obsessive-compulsive disorder?

Although the exact cause of OCD is not fully understood, studies have shown that a combination of biological and environmental factors may be involved.

Biological factors

The brain is a very complex structure. It contains billions of nerve cells — called neurons — that must communicate and work together for the body to function normally. The neurons communicate via electrical signals. Special chemicals, called neurotransmitters, help move these electrical messages from neuron to neuron. Research has found that patients with OCD have over activity in specific portions of their brain circuits. These circuits become even more active when the patient is experiencing their OCD symptoms. Effective treatment with either medication or behavior therapy can normalize this over activity.

Environmental factors

People with a tendency toward developing OCD may be impacted by environmental stressors. Certain environmental factors also might cause a worsening of symptoms. These factors include:

  • Abuse.
  • Changes in living situation.
  • Illness.
  • Death of a loved one.
  • Work- or school-related changes or problems.
  • Relationship concerns.

What are the symptoms of obsessive-compulsive disorder?

The symptoms of OCD may vary. Common obsessions include:

  • Fear of dirt or contamination by germs.
  • Fear of causing harm to another.
  • Fear of making a mistake.
  • Fear of being embarrassed or behaving in a socially unacceptable manner.
  • Fear of thinking evil or sinful thoughts.
  • Need for order, symmetry, or exactness.
  • Excessive doubt/the need for constant reassurance.

Common compulsions include:

  • Repeatedly bathing, showering, or washing hands.
  • Refusing to shake hands or touch doorknobs.
  • Repeatedly checking things, such as locks or stoves.
  • Constant counting, mentally or aloud, while performing routine tasks.
  • Constantly arranging things in a certain way.
  • Eating foods in a specific order.
  • Being stuck on words, images, or thoughts, usually disturbing, that won’t go away.
  • Repeating specific words, phrases, or prayers.
  • Needing to perform tasks a certain number of times.
  • Collecting or hoarding items with no apparent value.

Last reviewed by a Cleveland Clinic medical professional on 06/02/2014.


  • The National Institute of Mental Health (NIMH). Obsessive-Compulsive Disorder, OCD Accessed: 6/2/2014
  • Eisendrath SJ, Lichtmacher JE. Chapter 25. Psychiatric Disorders. In: Papadakis MA, McPhee SJ, Rabow MW. eds. CURRENT Medical Diagnosis & Treatment 2014. New York, NY: McGraw-Hill; 2014.
  • Bipolar and Related Disorders. In: Diagnostic and Statistical Manual of Mental Disorders, DSM-5. American Psychiatric Publishing, Incorporated; 2013.

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