Obsessive-compulsive disorder is an anxiety disorder characterized by recurrent thoughts, feelings, ideas or sensations (obsessions) or behaviors that makes a person feel driven to perform (compulsions). A person may have both obsessions and compulsions. 

An example of obsessive-compulsive disorder is excessive, repeated handwashing to ward off infection.

Obsessive-compulsive disorder (OCD) was previously believed to be rare. However, recent data shows that about 7 million Americans have the condition.

OCD usually is noticed between the ages of 20 and 30. The majority of those who will develop it show symptoms by age 30.

There are several psychological theories about the cause of OCD, but none have been confirmed. Some reports have linked OCD to head injury and infections. Several studies have shown that there are brain abnormalities in patients with OCD, but more research is needed.

About 20% of those with OCD have motor tics, suggesting the condition may be related to Tourette syndrome.   However, this link is not clear.

• Obsessions or compulsions that cause significant distress or interfere with everyday life
• Obsessions or compulsions are not due to medical illness or drug use

The person usually recognizes that the behavior is excessive or unreasonable.

The person's own description of the behavior usually leads to diagnosis of the disorder. A physical exam is performed to rule out physical causes, and a psychiatric evaluation is given to rule out other psychiatric disorders. Questionnaires, such as the Yale-Brown Obsessive Compulsive Scale, can help diagnosis OCD and track the progress of treatment.