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What is obsessive compulsive disorder (OCD)?

Updated Tuesday, 31st July 2012

Find out more about obsessive compulsive disorder (OCD), an anxiety related disorder in which people worry excessively about particular issues

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Obsessive compulsive disorder is an anxiety related disorder in which  people worry excessively about particular issues. This usually includes both obsessions and compulsions.

An obsession is a persistent disturbing and intrusive thought. The most  common is  worrying  about contamination from dirt or germs.

These obsessions are not the same as the general anxieties that we experience as part of our everyday lives. They can be extremely debilitating  and interfere with a person’s ability to carry out normal daily activities.  

This is in stark contrast to someone who might simply like to keep their home neat and tidy or is particularly fussy about their appearance.  

There are many types of obsessions, for example: an excessive concern with order and symmetry, worrying religious sexual thoughts and  fear of harming others or being harmed. 

Obsessions will usually have an associated compulsion. This is a repetitive behaviour that a person feels driven to carry out. It can be performed to reduce anxiety or guilt, or in a belief that it will prevent something harmful happening.

It can be a physical action , such as checking that a door is locked, or a mental act, such as  counting a number of steps or  repeating a particular phrase. 

Common compulsions 

The most common compulsions are those of checking, cleaning or repeating an action. For example a person who worries that they may have left the gas on, may repeatedly check that the taps are off.  They may feel the need to do this frequently throughout the day and night and make a physical check, even when they can see that the taps are off, or have been told by others that  is the case.    

A person who has an obsessive anxiety about contamination by germs may carry out  repeated  handwashing or cleaning activities.  The time consuming nature of these compulsive behaviours can significantly restrict a person’s social and work lives.

It is common for this person's family to become involved in these anxieties and behaviours. They may provide constant reassurance about an issue, or help to carry out the compulsion, for example support in carrying out cleaning rituals. OCD often  has a serious negative impact on family relationships.  


OCD is caused by a combination of factors. There is some evidence that a traumatic event may be associated with the development of OCD. However, a key issue is how  the event is perceived, rather than the type of event itself.

Events that might generally be seen as positive can also be associated with OCD. There are genetic and cognitive factors in OCD, which argue against a simple environmental ‘triggering’ of OCD. 

OCD can begin in childhood and disrupt a young person’s social, educational and emotional development. It's therefore  important that it's detected early. Appropriate early treatment typically produces better outcomes for the young person than later intervention.  


A complication with OCD is that whilst it typically begins in adolescence or early adulthood, people with OCD may not seek professional help and support for many years.  This is an unfortunate situation as OCD responds well to treatment.

One approach which works well for children and adults is  Exposure and Response Prevention (ERP), in which people are supported by a skilled therapist in repeatedly facing up to their anxiety-invoking situations (exposure), whilst resisting carrying out their compulsive behaviors (response prevention).

For example in a young person who has an obsession about germs and compulsively washes their hands will find that their anxiety levels will decrease if they stay in contact with a ‘contaminated object’ and resist the urge to subsequently wash their  hands. Over time their anxiety levels decrease and the compulsion to wash their hands reduces.

The approach begins with situations that provoke relatively low levels of anxiety and then moves on to more challenging situations. The exposure task is repeated at least a couple of times each day. At first this happens with the therapist and then becomes combined with the person carrying out the ERP tasks on their own.  

A key part of the approach can be to work with a persons’s family, who over time have become used to supporting the persons behaviour.  


Drug treatments can also be used effectively in combination with ERP. The most common medication is a type of antidepressant known as selective serotonin reuptake inhibitors (SSRIs). These increase levels of a substance called serotonin in the brain.  

There  are  potential adverse reactions, such as an increased risk of self harm and suicidal thoughts and particular care is taken in the use of such drugs with children. 

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