Obsessive-compulsive disorder (OCD) affects people differently, but usually causes a particular pattern of thought and behaviour.

This pattern has four main steps:

-obsession – where an unwanted, intrusive and often distressing thought, image or urge repeatedly enters your mind
-anxiety – the obsession provokes a feeling of intense anxiety or distress
compulsion – repetitive behaviours or mental acts that you feel driven to perform as a result of the anxiety and distress caused by the obsession
temporary relief – the compulsive behaviour brings temporary relief from anxiety, but the obsession and anxiety soon return, causing the cycle to begin again.

Obsessive thoughts
Almost everyone has unpleasant or unwanted thoughts at some point in their life, such as a concern that they may have forgotten to lock the door of the house or that they may contract a disease from touching other people, or even sudden unwelcome violent or offensive mental images.

Most people are able to put these types of thoughts and concerns into context, and they can carry on with their day-to-day life. They do not repeatedly think about worries they know have little substance.

However, if you have a persistent, unwanted and unpleasant thought that dominates your thinking to the extent it interrupts other thoughts, you may have developed an obsession.

Some common obsessions that affect people with OCD include:

-fear of deliberately harming yourself or others – for example, fear you may attack someone else, even though this type of behaviour disgusts you
-fear of harming yourself or others by mistake or accident – for example, fear you may set the house on fire by accidentally leaving the cooker on
fear of contamination by disease, infection or an unpleasant substance
-a need for symmetry or orderliness – for example, you may feel the need to ensure all the labels on the tins in your cupboard face the same way

Compulsive behaviour

Compulsions arise as a way of trying to reduce or prevent the harm of the obsessive thought. However, this behaviour is either excessive or not realistically connected at all.

For example, a person who fears becoming contaminated with dirt and germs may wash their hands repeatedly throughout the day, or someone with a fear of causing harm to their family may have the urge to repeat an action multiple times to try to “neutralise” the thought of harm. This latter type of compulsive behaviour is particularly common in children with OCD.

Most people with OCD realise that such compulsive behaviour is irrational and makes no logical sense, but they cannot stop acting on their compulsion.

Some common types of compulsive behaviour that affect people with OCD include:

-cleaning and hand washing
-checking – such as checking doors are locked, or that the gas or a tap is off
counting
-ordering and arranging
-hoarding
-asking for reassurance
-repeating words silently
-extensively “overthinking” to ensure the feared consequence of the obsession does not occur – for example, if you fear you may act violently
thinking “neutralising” thoughts to counter the obsessive thoughts
-avoiding places and situations that could trigger obsessive thoughts

Not all compulsive behaviours will be obvious to other people.