Obsessive-Compulsive Disorder is characterized by the presence of obsessions, compulsions or both.

Obsessions are defined by

• Recurrent and persistent thoughts, urges, or images that are experienced, at some time during the disturbance, as intrusive and unwanted and that in most individuals cause marked anxiety or distress.
• The person attempts to ignore or suppress such thoughts, urges, or images, or to neutralize them with some other thought or action (i.e. by performing a compulsion).

Compulsions are defined by

• Repetitive behaviors (hand washing, checking, ordering, repeating actions) or mental acts (praying counting repeating words silently) that the individual feels driven to perform in response to an obsession or according to rules that must be applied rigidly.
• The behaviors or mental acts are aimed at preventing or reducing anxiety or distress, or preventing some dreaded event or situation; however, these behaviors or mental acts are not connected in a realistic way with what they are designed to neutralize or prevent or are clearly excessive.

The obsessions or compulsions are time-consuming (e.g. take more than an hour per day) or cause clinically significant distress or impairment in social, occupational, or other important areas of functioning.