People who suffer from writer's cramp are far more likely to have signs of obsessive-compulsive disorder, say researchers.

Both could be caused, it is claimed, by a single malfunctioning part of the brain.

The research, carried out by a team at the Kyoto University Hospital, looked at a number of patients with different conditions which can cause discomfort or even pain in the hands and arms.

All were then given a psychometric questionnaire to see if they had any obsessive-compulsive symptoms.

These might include over-zealous washing or tidying rituals which cause anxiety if left incomplete.

An obsessive-compulsive disorder (OCD) sufferer might feel compelled to hoard materials or repeatedly check locks and light switches.

Fivefold chance

Remarkably, those with writer's cramp were five times more likely to display obsessive compulsive symptoms than those with the other conditions.

The researchers believe this backs up earlier anecdotal evidence of the link between writer's cramp and OCD.

They suggest there is growing evidence the root for both conditions lies in a part of the brain called the basal ganglia.

People who regularly get writer's cramp may be suffering from dystonia, a definition applied to a wide variety of conditions in which people suffer involuntary and often painful sustained muscle spasms.

Some types are thought to have to have a genetic source, often running in families.

Dr Kailash Bhattia, a consultant neurology from the National Hospital for Neurology and Neurosurgery in London, said he had not come across any association between writer's cramp and OCD.

He said: "No-one really knows what causes writer's cramp or any other dystonia.

"It's possible however, that people who suffer obsessive behaviour are more prone to strain injury because they are trying so hard to make their writing neat and tidy."

The research was published in the Journal of Neurology and Neurosurgery and Psychiatry.