Obsessive-compulsive disorder (OCD)

Explains what obsessive-compulsive disorder (OCD) is, including possible causes and how you can access treatment and support. Includes tips for helping yourself, and guidance for friends and family.

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What causes OCD?

There are different theories about why OCD develops. None of these theories can fully explain every person’s experience, but researchers suggest that these are likely to be involved in causing OCD:

Even though we don't fully understand what causes OCD it can still be successfully treated.

‘Dysfunctional’ beliefs

One theory suggests that OCD develops because of ‘dysfunctional’ beliefs and interpretations.

If you experience OCD you might believe that you have more responsibility for a situation than you actually do. Because of this, your reaction may be out of proportion.

For example, many people experience sudden and intrusive thoughts, such as thinking that they might push someone in front of a train on a crowded platform. Most people dismiss it as a passing thought and do not believe they would actually do it.

If you have 'dysfunctional' beliefs you might think that you could actually act on the intrusive thought. This makes you anxious or scared. You may develop a compulsion to try and prevent it happening. This could start an OCD cycle.

Personal experience

Some theories suggest that OCD is caused by personal experience. For example:

  • if you've had a painful childhood experience or suffered trauma or abuse, you might learn to use obsessions and compulsions to cope with anxiety. However this theory doesn't explain why people who can't point to any painful experiences might experience OCD.
  • if your parents had similar anxieties and showed similar kinds of compulsive behaviour - and so you learned that compulsions are a coping technique.
  • ongoing anxiety or stress or being part of a stressful event like a car accident could trigger the development of OCD or make it worse. Our pages on managing stress have more information on how to help yourself and get support for stress.

Biological factors

Some biological theories suggest that a lack of the brain chemical serotonin may have a role in OCD. However, experts disagree about what that role is. It's unclear whether a lack of serotonin causes OCD or is the effect of having the condition.

Studies have also looked at genetic factors and how different parts of the brain might be involved in causing OCD, but have found nothing conclusive.

Biological theories do not explain why the condition develops differently in different people; for example, why one person might develop a contamination obsession while another develops an obsession about harming.

You can read more about the possible causes of OCD on OCDUK's website.

 Is childhood OCD caused by an infection?

Some experts have noted that some children seem to develop OCD symptoms very suddenly after having a streptococcal (or strep) infection such as strep throat or scarlet fever. However no one knows why this can happen, and no research has yet been able to identify a physical cause to explain the link. Some children show OCD symptoms for a while and then they fade.


This information was published in July 2016. We will revise it in 2019.

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