People who are left-handed are twice as likely as right-handers to suffer from bowel disease, claim scientists.

A study of more than 20,000 people in the UK found that the risk of inflammatory bowel disease - usually Crohn's disease or ulcerative colitis - doubled in left-handed people.

Although the prevalence of left-handedness in the general population is around one in ten, 21% of the people found to have inflammatory bowel disease were left-handed.

The research, by a team at the Royal Free Hospital and University College Medical School in London, comes after earlier studies showed left-handers are at increased risk of other conditions such as asthma and diabetes.

Symptoms

Ulcerative colitis is a condition characterised by inflammation of the colon - large intestine - and rectum. Common symptoms of Crohn's disease, which is most common in 15 to 25 year olds, include recurrent abdominal pains, fever, nausea, vomiting, weight loss and diarrhoea.

Dr Danielle Morris, a research fellow in gastroenterology and epidemiology who led the study, told BBC News Online: "These results might be important because left-handedness has been associated with asthma and diabetes which are thought to be of an auto-immune cause. It might be important in finding out why.

"The reasons are uncertain and speculative. Development of the brain and left-handedness is partly genetic and there is a genetic pre-disposition to inflammatory bowel disease.

"It is probably more likely they might have a common environmental factor, such as infection in early life."

The academic department of medicine, where she is based, has been trying to track down early risk factors for inflammatory bowel disease and the results of the study, being presented to a British Society of Gastroenterology conference in Birmingham, may help in the search.

But she added: "At the moment, it is an interesting but unexplained finding."