Merck Manual

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Obsessive-Compulsive Disorder (OCD)


Katharine Anne Phillips

, MD, Weill Cornell Medical College;

Dan J. Stein

, MD, PhD, University of Cape Town

Reviewed/Revised Jul 2023
Topic Resources

Obsessive-compulsive disorder is characterized by obsessions, compulsions, or both. Obsessions are recurring, persistent, unwanted, anxiety-provoking, intrusive ideas, images, or urges. Compulsions (also called rituals) are certain actions or mental acts that people feel driven to repeatedly perform to try to lessen or prevent the anxiety caused by the obsessions.

  • Many obsessive-compulsive thoughts and behaviors are related to concerns about harm or risk.

  • Doctors diagnose the disorder when a person has obsessions, compulsions, or both.

  • Treatment may include exposure therapy (with prevention of compulsive rituals) and certain antidepressants (selective serotonin reuptake inhibitors or clomipramine).

OCD differs from psychotic disorders, which are characterized by loss of contact with reality, although in a very small minority of OCD cases there is no insight. OCD also differs from obsessive-compulsive personality disorder Obsessive-Compulsive Personality Disorder Obsessive-compulsive personality disorder (which is different from obsessive-compulsive disorder) is a mental health condition that is characterized by a pervasive preoccupation with orderliness... read more , although people with these disorders may have some of the same characteristics, such as being orderly, reliable, or perfectionistic.

Overview of Obsessive-Compulsive Disorder (OCD)

Symptoms of OCD

People with obsessive-compulsive disorder (OCD) have obsessions—thoughts, images, or urges that occur over and over even though people do not want them to. These obsessions intrude even when people are thinking about and doing other things. Also, obsessions usually cause great distress or anxiety. The themes of the obsessions include harm (to self or others), cleaning or contamination, forbidden or taboo thoughts (for example, aggressive or sexual obsessions), and the need for symmetry.

Common obsessions include the following:

  • Concerns about contamination (for example, worrying that touching doorknobs will cause disease)

  • Doubts (for example, worrying that the front door was not locked)

  • Concern that items are not perfectly lined up or even

Because the obsessions are not pleasurable, people often try to ignore and/or control them.

Compulsions (also called rituals) are one way people respond to their obsessions. For example, they may feel driven to do something—repetitive, purposeful, and intentional—to try to prevent or relieve the anxiety caused by their obsessions.

Common compulsions include the following:

  • Washing or cleaning to be rid of contamination

  • Checking to allay doubt (for example, checking many times to make sure a door is locked)

  • Counting (for example, repeating an action a certain number of times)

  • Ordering (for example, arranging tableware or workspace items in a specific pattern)

Most rituals, such as excessive handwashing or repeated checking to make sure a door has been locked, can be observed. Other rituals, such as repetitive counting in one's mind or quietly mumbling statements intended to diminish danger, cannot be observed.

Rituals may have to be done in a precise way according to rigid rules. The rituals may or may not be logically connected to the obsession. When compulsions are logically connected to the obsession (for example, showering to avoid being dirty or checking the stove to prevent fire), they are clearly excessive. For example, people may shower for hours each day or always check the stove 30 times before they leave the house. All obsessions and rituals are time-consuming. People may spend hours each day on them. They may cause so much distress or interfere with functioning so much that people are incapacitated.

Most people with OCD have both obsessions and compulsions.

Most people with OCD are at least somewhat aware that their obsessive thoughts do not reflect actual risks or reality and that their compulsive behaviors are excessive. However, a few people are convinced that their obsessions are well-founded and that their compulsions are reasonable.

Most people with OCD are aware that their compulsive behaviors are excessive. Thus, they may perform their rituals secretly, even though the rituals may occupy several hours each day.

As a result of OCD symptoms, relationships may deteriorate, and people with OCD may do less well in school, at work, or in other aspects of daily functioning.

Did You Know...

  • Most people with obsessive-compulsive disorder know that their obsessions and compulsions are irrational.

Diagnosis of OCD

  • A doctor's evaluation based on specific psychiatric diagnostic criteria

Doctors diagnose obsessive-compulsive disorder based on symptoms: the presence of obsessions, compulsions, or both. The obsessions or compulsions must be at least one of the following:

  • Time-consuming

  • Cause significant distress or interfere with the person's ability to function

Treatment of OCD

  • Exposure and ritual prevention therapy; cognitive therapy is often added

  • Certain antidepressants

Exposure and ritual (response) prevention therapy, a type of cognitive-behavioral therapy Psychotherapy Extraordinary advances have been made in the treatment of mental illness. As a result, many mental health disorders can now be treated nearly as successfully as physical disorders. Most treatment... read more , is often effective in treating obsessive-compulsive disorder. Exposure therapy involves gradually and repeatedly exposing people to whatever situations or people triggers obsessions, rituals, or discomfort while asking them not to perform the compulsive ritual (ritual prevention therapy). Discomfort or anxiety gradually diminishes during repeated exposure as people learn that rituals are unnecessary for decreasing discomfort. The improvement usually persists for years, perhaps because people who have mastered this approach are able to continue to practice it after formal treatment has ended. Cognitive therapy is often added to exposure and ritual prevention therapy.

Selective serotonin reuptake inhibitors Selective serotonin reuptake inhibitors (SSRIs) Several types of medications can be used to treat depression: Selective serotonin reuptake inhibitors (SSRIs) Norepinephrine-dopamine reuptake inhibitors, serotonin modulators, and serotonin-norepinephrine... read more (such as fluoxetine), a type of antidepressant, and clomipramine, a tricyclic antidepressant, are often effective. Higher doses than are commonly used for the treatment of depression may be needed. Many experts believe that a combination of exposure and ritual prevention therapy along with medication is the best treatment, especially for more severe symptoms.

Psychodynamic psychotherapy (which emphasizes the identification of unconscious patterns in current thoughts, feelings, and behaviors) and psychoanalysis have generally not been effective for people with obsessive-compulsive disorder.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Prozac, Prozac Weekly, Sarafem, Selfemra
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