Obsessive–compulsive disorder (OCD) is an anxiety mental disorder characterized by involuntary intrusive thoughts and compulsive behaviors. When a sufferer begins to acknowledge these intrusive thoughts instead of dismissing them, which is voluntary, the sufferer then develops a great degree of anxiety based on the doubt that something has happened or will happen. The sufferer feels compelled to voluntarily perform irrational, time-consuming, and distressing physical behaviors.
Sufferers often try to keep their compulsive behaviors hidden from others, often to avoid embarrassment, humiliation or to avoid being seen as strikingly odd or different from others. If the condition is not realized by an undiagnosed sufferer, they may scold themselves in frustration as to why they are thinking or acting the way they are. Although the acts of those who have OCD may appear paranoid and come across to others as psychotic, this could not be farther from the truth. An OCD sufferer is able to recognize their thoughts and subsequent actions as irrational; they do not believe that they are in any way more rational than anyone else, which is what makes the illness so distressing, as the psychological self-awareness of the irrationality of the disorder may be extremely painful. They are plagued by doubt and uncertainty, hence the condition is also referred to as the "doubting disease". The biggest challenge OCD sufferers face is learning to live in doubt, without constant reassurance.
OCD is the fourth most common mental disorder and is diagnosed nearly as often as the physiological ailments asthma and diabetes mellitus. In the United States, one in 50 adults has OCD. The phrase "obsessive–compulsive" has become part of the English lexicon, and is often used in an informal or caricatured manner to describe someone who is meticulous, perfectionistic, absorbed in a cause, or otherwise fixated on something or someone. Although these signs are often present in OCD, a person who exhibits them does not necessarily have OCD, and may instead have obsessive–compulsive personality disorder (OCPD) or some other condition.