Obsessive compulsive disorder (OCD) is a complex disorder that affects people differently, although it usually involves set patterns of thinking and behavior.

Usually, the particular patterns that are seen in obsessive compulsive disorders involve the following four stages:

• Obsession - The person is overwhelmed by a constant and obsessive concern or fear
• Anxiety - The obsession gives rise to intense anxiety and distress or panic
• Compulsion - In order to reduce this anxiety or distress, the patient adopts a certain behavior. For example, if the fear is that the house may be burgled, the behviour adopted may be checking several times that all windows and doors are locked before leaving home.
• Temporary relief - Adopting the compulsive behavior provides temporary relief from the distress or anxiety. However, this relief is only short term and both the obsessive thought and anxiety return, followed again by the compulsive behavior.

Almost all individuals experience obsessive thoughts at some point in their lives and may worry about their job security or whether or not their partner is being faithful, for example. However, if a person cannot put these thoughts into context and instead finds their concerns are overwhelming and affect their day-to-day living, then they may have developed an obsession.

Compulsions are actions a person with OCD carries out as a way of preventing the harm caused by the thought they are obsessed with. However, the action may be excessive or may not realistically prevent the harm. For example, a fear of infection may lead to excessive and repetitive hand washing or the patient might repeat a certain unconnected ritual to “neutralise” their thoughts about harming themselves or others. This type of compulsion is commonly seen in children.Some common examples of the obsessions people develop in cases of OCD include fear they may hurt or harm themselves or someone else either on purpose or accidentally, fear of being contaminated by a disease or infection and fear of committing an offence against their religious beliefs. People with OCD may also experience a continued need for order or symmetry such as ensuring objects are lined up in a certain way, for example.

A person suffering from OCD is often aware that their compulsions are irrational but they still feel the need to act on their compulsion. Common compulsive behaviors include hand washing, cleaning, checking for locked doors, checking gas tap is off, arranging and ordering things, counting, hoarding, repeating words and asking for reassurances.