Gene for obsessive behaviour

Excessive hand washing is a symptom of OCD

Scientists have uncovered a gene which they believe may play a role in causing obsessive-compulsive disorder (OCD).

They hope that their work will allow earlier identification and treatment of people who are at greatest risk of developing the potentially debilitating condition.

They also hope it will lead to more effective therapies.

Obsessive-compulsive disorder is an anxiety disorder in which people are persistently compelled to carry out ritualised behaviour in response to recurring thoughts which are often completely irrational.

For instance, sufferers often become obsessed with the notion that they are contaminated with germs, leading to hour upon hour of washing.

Common obsessions

Fear of contamination

Fear of causing harm to another

Fear of making a mistake

Fear of behaving in a socially unacceptable manner

Need for symmetry or exactness

The condition can become so bad that it prevents people from leading a normal life.

The causes of the disorder, which affects at least five million Americans and a million Britons, are still obscure.

However, it is likely that the condition has a genetic element as it tends to run in families.

Brain chemical

A popular theory is that a genetic fault leads to a disruption of levels of a brain chemical called serotonin.

Serotonin plays a crucial role in helping nerve cells to communicate effectively with each.

It is possible that the receptors that tell how much serotonin should be released may be altered in OCD patients.

Common Compulsions

Hand washing

Ordering

Checking

Praying

Repeating words silently

Researchers from the University of Toronto studied OCD patients and their parents.

They focused on a gene that plays a central role in determining how one of the serotonin receptors works.

And they found that OCD patients were more likely to inherit a particular version of the gene from their parents.

The findings suggest that OCD is indeed linked to a disruption of the serotonin system.

Professor Kevin Gournay, of the UK Institute of Psychiatry, told BBC News Online: "In light of the research findings over last decade I am now firmly of the view that OCD is predominantly a biological condition with a complex genetic background.

"I'm also sure that environmental factors may in some cases trigger it. However all in all it is, in my view, mostly genetic."

Ian Hancock, director of psychology at Dumfries and Galloway Primary Care NHS Trust, said it would be wrong to discount the effect that environmental factors and personal experience had on the development of OCD.

He told BBC News Online: "I have no problem with the idea that person's genetic make-up may make them more likely to develop OCD, but I do have a problem with the idea that it is set in stone and so shall be."

The research is published in the journal Molecular Psychiatry.