While doctors have known for some time that psychological therapy can reduce the symptoms of irritable bowel syndrome -- a gastrointestinal disorder -- in the short term, a new study has found that the benefits can extend up to one year after the completion of the therapy.

The beneficial effects of psychological therapy for irritable bowel syndrome (IBS) appear to last at least six to 12 months after the therapy has concluded, the study said.

"Our study is the first one that has looked at long-term effects," said senior author Lynn Walker, professor of pediatrics at Vanderbilt University Medical Center in Tennessee, US.

The study analysed the results of 41 clinical trials involving more than 2,200 patients from a number of different countries.

"We found that the moderate benefit that psychological therapies confer in the short term continue over the long term. This is significant because IBS is a chronic, intermittent condition for which there is no good medical treatment," Walker noted.

Characterised by chronic abdominal pain, discomfort, bloating, diarrhoea or constipation, IBS is classified as a disorder of the "brain-gut axis."

Although no cure is known, there are treatments to relieve symptoms including dietary adjustments, medication and psychological interventions.

"Western medicine often conceptualizes the mind as separate from the body, but IBS is a perfect example of how the two are connected," first author Kelsey Laird, doctoral student at University, pointed out.

"Gastrointestinal symptoms can increase stress and anxiety, which can increase the severity of the symptoms. This is a vicious cycle that psychological treatment can help break," Laird explained.

The studies that the researchers analysed included a number of different types of psychological therapies, including cognitive therapies, relaxation and hypnosis.

The findings showed no significant difference in the effectiveness of different types of psychotherapy.

The study was published in the journal Clinical Gastroenterology and Hepatology.