What causes OCD?

There are different theories about why OCD develops, but none of these theories have been found to fully explain every person’s experience.

‘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. However, if you have OCD, you are more likely to believe that you might act on the thought. This makes you anxious or scared, and so you may then develop a compulsion to try and prevent it happening. This could start an OCD cycle (see ‘Compulsion’).

Personal experience

Some psychological theories suggest that OCD is caused by personal experience. It is thought that if you have 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 does not explain why people who cannot point to any painful experiences might experience OCD.

It could also be that one or both of your parents may have had similar anxiety and have shown similar kinds of behaviour (such as obsessional washing), and you learned to use this type of behaviour as a coping technique.

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, and it is unclear whether a lack of serotonin causes OCD or is the effect of having the condition. Some studies have also looked at genetic factors, and how different parts of the brain might be involved in causing OCD, but have not yet found anything conclusive.

However, biological theories do not provide any explanation for how the condition develops differently in different people; for example, why one person might develop a contamination obsession while another develops an obsession about harming.

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, it is currently not known why this might occur and no research has yet been able to identify a physical cause to explain the link.

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