Obsessive compulsive disorder - Causes of obsessive compulsive disorder

The exact cause of obsessive compulsive disorder (OCD) is unknown, but a number of theories have been suggested. These are explained below.

Genetic factors

There is evidence to suggest that OCD may be the result of certain inherited genes (units of genetic material) that affect the development of the brain.

No specific genes have been linked to OCD, but there is some evidence that the condition runs in families. For example, a person with OCD is four times more likely to have another family member with the condition compared with someone who does not have OCD.

Genetic and family studies have also shown that OCD may be related to other conditions, such as:

• tics rapid, repeated, involuntary contractions of a group of muscles
• Tourette s syndrome a condition that causes a person to make repetitive movements or sounds

Some people with OCD may also have tics or Tourette s syndrome.

Brain abnormalities

Brain imaging studies have shown that people with OCD have abnormalities in some parts of their brain, such as increased blood flow and activity.

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

Serotonin

The chemical serotonin also seems to play a part in OCD. Serotonin is a neurotransmitter, a chemical that the brain uses to transmit information from one brain cell to another.

Exactly how serotonin contributes to OCD is unknown, but medication that increases the serotonin levels in the brain, such as certain antidepressants, have successfully helped to treat the symptoms of OCD.

Infection

There have been reports of some children and young people developing OCD after an infection caused by streptococcal bacteria. It is possible that the antibodies (infection-fighting proteins) produced by the body react with part of the brain and cause OCD.

Life events

An adverse life event, such as a bereavement or family break-up, may trigger OCD in people who already have a tendency to the condition for example, due to genetic factors.

This life event could also affect the course of your condition. For example, the death of a loved one may trigger a fear that someone in your family will be harmed. Stress, which can also be caused by life events, seems to make OCD symptoms worse. However, stress on its own is not a cause of the condition.

Family involvement

Your upbringing is not thought to cause OCD. However, some factors could make OCD more likely to develop. For example, having parents who are very overprotective.