Causes of obsessive compulsive disorder (OCD) 

Despite much research being carried out into obsessive compulsive disorder (OCD), the exact cause of the condition has not yet been identified.

However, a number of different factors that may play a role in the condition have been suggested. These are described below.


Genetics is thought to play a part in some cases of OCD. Research suggests OCD may be the result of certain inherited genes that affect the development of the brain.

Although no specific genes have been linked to OCD, there is some evidence that suggests a person with OCD is more likely to have another family member with the condition compared with someone who does not have OCD.

However, it is possible there may sometimes be other reasons for this. For example, it has been suggested some people may "learn" OCD as a result of witnessing other family members with the condition.

Brain differences

Brain imaging studies have shown some people with OCD have differences in certain parts of their brain, including increased activity and blood flow, and a lack of the brain chemical serotonin.

The areas of the brain affected deal with strong emotions and how we respond to those emotions. In the studies, brain activity returned to normal after successful treatment with cognitive behavioural therapy (CBT) or selective serotonin reuptake inhibitors (SSRIs).


Serotonin may play a part in OCD. This brain chemical transmits information from one brain cell to another and is known as a neurotransmitter.

Serotonin is responsible for regulating a number of the body's functions, including mood, anxiety, memory and sleep.

It is not known for sure how serotonin contributes to OCD, but some people with the condition appear to have decreased levels of the chemical in their brain.

Medication that increases the levels of serotonin in the brain, such as certain types of antidepressant, have proven effective in treating OCD.

Life events

OCD may be more common in people with a history of having experienced emotional, physical or sexual abuse, neglect, social isolation, teasing or bullying.

An important life event, such as a bereavement, family break-up, a new job, pregnancy or childbirth, may also trigger OCD in people who already have a tendency to develop the condition – for example, because of genetic factors – and may affect the course of the condition.

For example, the death of a loved one may trigger a fear that someone in your family will be harmed.

Stress seems to make the symptoms of OCD worse, but does not cause OCD on its own.


People with certain personality traits may be more likely to have OCD. For example, if you are a neat, meticulous, methodical person with high standards – a "perfectionist" – you may be more likely to develop the condition.

OCD may also be a result of simply being more prone to becoming tense and anxious than most people, or having a very strong sense of responsibility for yourself and others.

Page last reviewed: 27/10/2014

Next review due: 27/10/2016