Obsessive-compulsive disorder (OCD) is an anxiety disorder in which a person becomes trapped in a pattern of intrusive and unwanted thoughts and repeatedly performs tasks or rituals to get rid of the thoughts. Fear of contamination is one of the most common obsessions, and hand-washing and checking that something has been done are the most common compulsions.

• Obsessions are thoughts and worries that will not go away. These thoughts are usually irrational and cause anxiety. For instance, the person may constantly worry, "My hands are dirty. I will get a disease." Obsessions usually lead to irrational behaviors (compulsions).
• Compulsions are recurring behaviors that a person feels a strong urge to do in response to obsessive thoughts or worries. For example, a person who has an obsession with dirty hands and disease may wash his or her hands over and over again.

In a person with obsessive-compulsive disorder, attempts to control his or her obsessions and resist the urge to perform certain compulsive behaviors may cause extreme anxiety or panic attacks.

Treatment includes medicines and counseling.