Anxiety can generate excessive preoccupation, involuntary and annoying mental images, which constitute an obsession. Under this strong, inner constraint a voluntary, but unreasoned, compulsory defence mechanism is set up: the compulsion. It takes the form of routines, mental acts (e.g. counting) or ritual gestures, which aim to neutralise the obsession and reduce anxiety.
Obsessions are uncontrollable. People with obsessive-compulsive disorder know their absurdity. They know it is borne out of their mind, and not grounded in reality. However, they cannot help but produce stereotyped and repetitive behaviours in response, which they are often aware of as being exaggerated. This may sometimes be accompanied by fear or disgust as the obsession may be distant from, or even contrary to, their personal values.
Some of the most common themes of these obsessions and their response in terms of behavioural disorders are:
- Cleanliness, fear of contamination: cleaning things or washing repeatedly.
- Order or symmetry: ordering, classifying, placing objects.
- Repeated doubts: counting, enumerating, checking.
- The fear of making mistakes: doing multiple checks.
- Thinking about sexuality or religion: performing magical, superstitious rituals.