Obsessive-compulsive disorder (OCD) is a psychiatric disorder most commonly characterized by a subject's obsessive, distressing, intrusive thoughts and related compulsions (tasks or "rituals") which attempt to neutralize the obsessions. Thus it is an anxiety disorder. It is listed by the World Health Organization as one of the top 10 most disabling illnesses in terms of lost income and diminished quality of life.
The phrase "obsessive-compulsive" has worked its way into the wider English lexicon, and is often used in an offhand manner to describe someone who is meticulous or absorbed in a cause (see also "anal-retentive"). Such casual references should not be confused with obsessive-compulsive disorder; see clinomorphism. It is also important to distinguish OCD from other types of anxiety, including the routine tension and stress that appear throughout life. Although these signs are often present in OCD, a person who shows signs of infatuation or fixation with a subject/object, or displays traits such as perfectionism, does not necessarily have OCD, a specific and well-defined condition.
To be diagnosed with obsessive-compulsive disorder, one must have either obsessions or compulsions alone, or obsessions and compulsions, according to the DSM-IV-TR diagnostic criteria. The Quick Reference to the diagnostic criteria from DSM-IV-TR (2000) describes these obsessions and compulsions:
In addition to these criteria, at some point during the course of the disorder, the sufferer must realize that his/her obsessions or compulsions are unreasonable or excessive. Moreover, the obsessions or compulsions must be time-consuming (taking up more than one hour per day), cause distress, or cause impairment in social, occupational, or school functioning. OCD often causes feelings similar to those of depression.