Obsessive-Compulsive Disorder commonly called OCD is a disorder involving obsessions and compulsions. It is considered a psychiatric disorder and classified as an anxiety disorder since most people who have OCD have substantial anxiety that causes distress and interferes with their daily function. OCD is also sometimes referred to as a biobehavioral disorder or a psychobiological disorder.
These terms are meant to convey the idea that it is a disorder of that involves brain function, behavior and psychological experiences. In the US we use diagnostic criteria listed in a manual published by the American Psychiatric Association to make diagnoses of psychiatric disorders. The current version of this manual is the DSM-IV-TR. According to this manual the diagnosis is made for an individual who has obsessions and or compulsions which cause distress, are time consuming (more than an hour a day) or significantly interfere with function.
The diagnosis is made if other disorders don't explain the symptoms or the symptoms are not caused by the effects of a substance (such as a drug that is being abused) or by some medical problem. Ordinarily people with OCD recognize that their obsessions and or compulsions are unreasonable at least part of the time. In some cases this recognition does not occur, in which case the person is described as having poor insight. Poor insight may be much more common in children.
Obsessions are recurrent and persistent thoughts, images, urges or impulses that are experienced as intrusive or inappropriate and that cause significant anxiety or other distress. The thoughts are not simply excess worries about real life problems. People with OCD attempt to suppress or neutralize these intrusive thoughts. Ordinarily they recognize the thoughts as products of their own mind rather than somehow imposed from without.
Compulsions are repetitive behaviors or mental acts that the person feels driven (compelled) to do typically in a very specific way or according to a set of rules. Common compulsions include washing, checking and ordering. Common mental compulsions include praying, counting, repeating words or phrases and mentally reviewing events.
Compulsions are intended to prevent or reduce distress often by preventing or ending some threat of adverse outcome. For example a person with OCD may wash to prevent illness when they believe they may have been exposed to contamination, or a person may check on the status of appliances to prevent a fire. Compulsions are not seen (by others) as realistic efforts to prevent these adverse events or are clearly excessive.
The diagnostic criteria specify the individual has obsessions and or compulsions. This presents the possibility that an individual could be diagnosed as having OCD on the basis of having obsessions and no compulsions or compulsions and no obsessions. The former state is sometimes referred to as Pure O. This is a description of an individual who reportedly has only obsessions. Expert consensus holds that this is actually a misnomer. People described as having Pure O are routinely found to have mental activity that can be described as compulsions or neutralizations. The term neutralization applies to a broader category of behaviors some of which may not be stereotyped enough to be called compulsions but which otherwise function the same way to reduce anxiety or distress and remove the threat of an adverse outcome. There are important treatment implications associated with this understanding so individuals who describe their problem as Pure O are informed about how they are engaging in compulsions or the equivalent typically on a mental level.
There is no term to describe people who appear to have compulsions but no obsessions although one might suggest they be called Pure C. On more careful examination it becomes clear that these people have obsessions but they may not be well elaborated or articulated. Individuals who don't seem to have obsessions will typically report not feeling “right” unless the compulsion is carried out and usually report a concern that this uncomfortable feeling will persist or perhaps worsen unless the compulsion is carried out. This can be understood as the feared adverse outcome that is central to obsessions.