Obsessive-compulsive disorder (OCD) is believed to be rooted in a biochemical imbalance of the brain. It is classified as an anxiety disorder that affects thoughts and actions. It is characterized by recurrent, disturbing thoughts called obsessions that produce symptoms such as repetitive, ritualized behaviors called compulsions. While most patients experience both obsessions and compulsions, some experience only obsessions (about 20%), or only compulsions (about 10%).
A person with OCD may try to get rid of obsessions by engaging in compulsions, or by avoiding situational triggers. These obsessions may present as intrusive images or unwanted impulses. Most often, compulsions are practiced by sufferers as a way to alleviate anxiety. It is also common for compulsions to trigger anxiety when they become overly demanding. A person with OCD may recognize that their thoughts and actions are pointless or excessive, but the drive can become so powerful that they have no control over the compulsion, despite knowing that it does not make sense.