Introduction

Obsessive-compulsive disorder (OCD) is one of the major anxiety disorders in the fourth edition of Diagnostic and Statistical Manual of Mental Disorders (DSM-IV: American Psychiatric Association, 1994). The disorder is characterized by persistent obsessions and compulsions that are time-consuming or cause marked distress or impairment and are perceived by the patient to be excessive or unreasonable. Obsessions are intrusive, recurrent, and persistent thoughts, images, or impulses that are unacceptable, unwanted, and usually associated with subjective resistance (Rachman and Hodgson, 1980). The content of the obsession is egodystonic in that it deals with themes that are inconsistent or even alien to one's sense of self, values, or usual ways of behaving (Purdon and Clark, 1999). Because of this the occurrence of the obsession is highly distressing for individuals with OCD, even though they may acknowledge that the intrusion is senseless and irrational (Rachman and Hodgson, 1980). The most commonobsessions involve concerns about dirt/disease contamination, accidents, unintended aggression or violence towards others, inappropriate sexual acts, mistakes, doubt, blasphemous thoughts, orderliness and symmetry, and hoarding.

Compulsions are repetitive, stereotypic, and intentional behavioral or mental responses that are subjectively experienced as an urge or pressure to act. The OCD patient may view the compulsion as excessive or exaggerated but the urge to act is not necessarily resisted in all cases. Compulsions are usually triggered by the occurrence of a distressing obsession.