Of all the lifestyle illnesses peculiar to a generation that is stressed-out, tired-out and flaked-out, one has persistently remained an enigma to the medical profession: irritable bowel syndrome.

IBS is thought to affect around eight million Britons, though with no confirmed cause, diagnosis is tricky and treatment of the debilitating symptoms – which include abdominal bloating and cramping, diarrhoea and constipation – even more difficult. But as researchers begin to unravel the complexities of the condition, it emerges that therapies focusing on the mind, not the body, are most effective.

A survey by Bu’Hussain Hayee, a clinical research fellow at University College Hospital, and Dr Ian Forgacs, a consultant gastroenterologist at King’s College Hospital, London, published in the BMJ recently concluded that approaches such as hypnotherapy, cognitive behavioural therapy (CBT) and antidepressant drugs could be most helpful.

According to Forgacs, IBS is a “complex mix of physical and emotional factors and people suffer for a variety of different reasons”. Typically, it is diagnosed when X-rays, blood tests, examination of the stool and other tests do not reveal any abnormality; patients are known to be more likely to suffer depression and somatisation (the conversion of mental problems into physical complaints). Yet despite the variation in underlying causes, mind-based treatments seem to help.

Many sufferers report that their IBS starts during or after a stressful period in their lives such as a divorce, sudden unemployment or a bereavement.

In other cases, it is linked to bacterial gastroenteritis – usually food poisoning – or a food intolerance. But so strong are the psychological underpinnings of the illness that Dr Nick Read, medical adviser to the IBS Network, says “it develops in patients with these problems only if something stressful is happening at the same time”. Read adds that the medical profession is increasingly prone to believe that “IBS is a gut reaction to emotional upheaval or upset”.

What is of interest to many researchers, including Forgacs, is how and why this somatisation takes place. One popular, but controversial, theory is that the human body has a second – hidden but powerful – brain known as the enteric nervous system that controls gut functions and reactions. “Certainly, the human body does seem to have both a conscious brain and a subconscious one that controls bodily functions such as hunger,” Forgacs says. “There are so many interactions between the two and it could explain why the majority of patients with anxiety problems will have alterations of gut function too.”

In Forgacs’s recent review, for example, even people with IBS in which depression was not diagnosed appeared to benefit from taking antidepressants. One explanation could be a link with the chemical serotonin, which is produced in the brain and is crucial to feelings of well-being. Many antidepressants work by altering serotonin levels in the brain. In a healthy, nondepressed person, once serotonin is released it triggers an intestinal reflex that ensures it is transported out of the bowel by a molecule known as the serotonin transporter (or sert) found in cells lining the gut wall. Research by Dr Michael Gershon, author of The Second Brain and head of anatomy and cell biology at Columbia University, suggests that people with IBS don’t have enough sert and so end up with too much serotonin, the consequence of which is diarrhoea.

In response to this intestinal imbalance, excess serotonin then floods the gut receptors causing them to shut down, which results in constipation. Gershon’s studies showed that mice with insufficient sert suffered IBS-like symptoms. “To be honest, we really don’t know why antidepressants work for IBS, just that they do,” Forgacs says.

The second brain theory could also help to explain the findings of other researchers, including those by Rona Moss-Morris, an associate professor of health psychology at the University of Southampton, who discovered in a study published earlier this year that the overanxious or highly driven are most at risk of developing the illness. Moss-Morris looked at 620 patients with gastroenteritis, none of whom had a history of IBS or chronic bowel disorder. A refusal to slow down when they had a stomach infection led to a much greater likelihood of them developing IBS, she says. “Instead of resting up, these driven people kept going until they collapsed,” Moss-Morris says. “The gastroenteritis appeared to trigger the symptoms, significantly more so than glandular fever, which we studied previously, but this all-or-nothing behaviour helped to prolong them.”

Moss-Morris suggests: “Patients who have ongoing IBS symptoms might benefit from a simple, early intervention of CBT, a means of changing thought processes from negative to positive that has been shown to be helpful.”

Last year, Dr Jeffrey Lackner, a psychiatrist at the State University of New York, reported that only four brief CBT sessions along with a self-study manual given to patients resulted in improvements in 73 per cent of his IBS patients.

Another approach is hypnotherapy. Peter Whorwell, Professor of Medicine and Gastroenterology at the University of Manchester, has been researching its use to treat IBS for more than 20 years and founded a dedicated unit at Wythenshawe Hospital, Manchester. In arecent study, 250 patients who had suffered with IBS for more than two years were given up to 12 one-hour sessions of hypnotherapy. When asked to assess their symptoms and anxiety levels preand posttreatment and for up to six years afterwards, 71 per cent of patients said that it had been of considerable help. Patients reported taking less medication and most said that the effects lasted up to five years.

How hypnotherapy works is unknown, but it is thought that IBS could be linked to problems with muscle movement or gut sensitivity and that the treatment may help patients to influence the release of hormones or gain better control over the nerve links between gut and brain. “Sufferers learn how to influence their gut function and then seem to be able to change the way the brain modulates their gut activity,”

Whorwell says. Critics argue that hypnotherapy is time-consuming and expensive – a recent review of published papers found insufficient evidence to recommend its widespread use. Even Whorwell concedes “it is not suitable for everyone and women tend to respond better than men”.

In spite of the scientific interest in mind-based therapies, Read stresses that there is still no cure. “It is one of those illnesses that may come and go according to what is going on in your life,” he says. “The important thing seems to be to learn how to adapt if it does recur.”

Treatments for specific symptoms – antispasmodics to relieve gut spasm and pain, antidiarrhoea medication and laxatives for constipation – may be prescribed by your doctor, says Read, “but they are not wonderful as they don’t address the root cause”.

Likewise, he says, “anti-depressants can be useful if the emotional tensions are ironed out” and can also work “directly on the gut to reduce spasm”. Diet can help – more fibre reduces constipation, avoidance of troublesome foods can eliminate side-effects and eating routinely can prevent upsetting the bowel – but in many cases, says Read, “patients find both diet and drugs disappointing”.

Often, says Penny Lunn, of the IBS Network, the most vital step is for patients to ask themselves what might have brought on the symptoms. “Is there anything making them anxious and depressed,” she says. “Can they manage their illness by adjusting their lifestyle? These are the kinds of things that we suggest they think about.”

The best preventive measure, Lunn says, is to lead a balanced life and not internalise worries and concerns.

“IBS can be very unpleasant,” says Forgacs. “It is sometimes difficult to relate to patients and many GPs that symptoms might need psychological treatment. They can’t get their heads around that. But IBS is such a complex problem and while we don’t understand why it happens, we do know that mind-based therapies seem to work.”