A new approach treats ME in children by involving the whole family - with remarkable results.

Just before Christmas 1999, Sarah Barnes caught a virus and didn't get better. Her GP referred her to a paediatrician, who suggested that she was suffering from chronic fatigue syndrome (CFS), also known as ME. "He told me not to take to my bed, not to get scared by information about CFS on the internet, and that I should get better by the summer. He didn't offer to see me again," says Sarah, now 16, from Greenwich.

A year later, she still wasn't better. Her legs ached, she couldn't sleep properly, she had headaches, she was barely going to school. "It was like having flu the whole time," she remembers. "When I tried to walk, it was like walking through treacle."

In January this year, CFS/ME was recognised as a genuine physical illness by the Government. "This is a real disease affecting real people," said the chief medical officer, Professor Sir Liam Donaldson. Yet there is no known cause, no official test for it, no treatment that has been proved effective by clinical trials – and therefore, no hope of a cure.

For the estimated 25,000 UK children, predominantly girls, who suffer from CFS, this normally means waiting until they get better – a process that could take years, leaving their education, social life and confidence in tatters. But a new pilot study carried out at Guy's, King's and St Thomas's School of Medicine offers hope to these sufferers. Before treatment, the 23 children attended school for an average of half a day a week. Of the 20 children who completed treatment, 95 per cent were in school full-time six months later.

But the findings will not be popular with some CFS sufferers and their supporters because the study was carried out not by doctors but by therapists. Brian Dow, spokesperson for Action for ME, gives the study a cautious welcome. "The illness is physical," he says. "This kind of psychological help cannot cure the underlying disease, but can help manage the symptoms."

Trudie Chalder, a reader in psychology and nursing, who led the study, disagrees. "I think the cognitive behavioural therapy [CBT] that we offer deals with the heart of the problem. There's no evidence to show that that view is correct. We're not just targeting anxiety and depression associated with having a physical illness – we are targeting the things that are crucial to the continuation of the symptoms."

The 23 children, aged 11 to 18, had been ill for an average of 2.4 years when they began treatment. They and their families were seen every fortnight for up to 15 hourly treatments. Initially, the therapy involved increasing the child's activity levels gradually and establishing a sleep routine. Sarah began regular cognitive behavioural therapy at the School of Medicine in March 2001 with nurse-therapist Vincent Deary. "Vincent and I agreed on the activities I would do," says Sarah. "At the beginning, I had to walk for 10 minutes a day and go to bed and get up at the same time. It didn't matter how I felt, I had to stick to the routine. I used to make a real fuss, but slowly I started to feel better." By August, on holiday in Devon, she was able to walk uphill to a party. "I couldn't get over the difference" she says.

Trudie Chalder says that the key is to break down the link between feeling fatigued and stopping exercise. "If your symptoms dictate what you do – ie, every time you're tired, you stop what you're doing – in the end you will be severely disabled, which is exactly what happens with these children. The symptoms are in control of them instead of them being in control of the symptoms. You need to gradually push through the tiredness, even though it's difficult," she says.

Many children with CFS are told to rest by their doctors, but Chalder says this is counter-productive. "The psychological and physical effects of inactivity are profound," she says. "People become more fatigued, weaker, more miserable and lose confidence. In fact, all the evidence shows that rest as a form of treatment for almost any illness is unhelpful."

Sarah was then encouraged to look at any negative or unhelpful thinking. "Vincent asked me to write down what I was feeling bad about, and then find a positive side to it," she explains." For Sarah, the disintegration of her social life was the worst part of having CFS. " I wasn't in touch with anyone. I hadn't been out with friends for eight months," she says. Now, she is going out again, has taken up yoga and goes to school until lunchtime four days a week. "I was so lucky to get on to the treatment with Vincent. I wouldn't be where I am now without it," says Sarah.

Trudie Chalder is confident that cognitive behavioural therapy could help many children with CFS. "It's not necessarily a magic cure, but because CBT is such a pragmatic approach not just to illness but to life, I can't see why it wouldn't be of benefit to everybody with CFS," she says. Action for ME's Brian Dow is more sceptical. "We found in different studies that CBT can be harmful because of the way that it's applied. Some practitioners have pushed people too fast," he says. "The most severely ill people don't seem to benefit from these rehabilitation programmes. CBT can help some but not all people."

Their difference of opinion stems from the dispute over what causes CFS. Unlike Brian Dow, Trudie Chalder believes that the roots of the illness are "multi-factorial". "A number of things may trigger off the fatigue in the first instance, possibly chronic stress or a change – quite a few of the children have reported difficulties at school prior to the onset of the illness. Often they get a virus and it's the straw that breaks the camel's back," she says.

Like Sarah Barnes, 89 per cent of the children involved in the study attributed the onset of their fatigue to a viral infection. But Sarah agrees with Chalder that her illness wasn't purely physical. "You can't say that I just suffered mental effects from a physical illness. When I get worked up, I feel physically awful. It was a mixture – it's different for everyone who has CFS." As a result, Sarah and her mother Deborah believe that the argument over whether CFS is a physical or psychological illness is unhelpful and misguided.

Similarly, Trudie Chalder reacts angrily to suggestions that CFS is "all in the mind". "I don't know what people mean when they talk about 'the mind' and 'the body'," she says. "We know that there's a very close relationship between cognition – how people think – and their physiological responses. Even as we think, that is a physiological mechanism. There is a lot of evidence, from all sorts of more clearly defined illnesses, that your thoughts and behaviour are very important in determining what happens to you physically."

Chalder also attacks the idea that psychological symptoms are less serious than physical ones. "Some people seem to think that if your illness is 'in the mind' somehow it's your fault and you may be imagining the symptoms. Clearly that's not the case. The symptoms are real."

The truth is that no one yet knows what causes CFS/ME and the arguments over it do not greatly help those who are suffering now. "There's been too much argument," agrees Action for ME's Brian Dow. "As long as the treatment is carried out in full collaboration with the patient and is sensitive to their physical capabilities, then it's valuable. We need to get on with helping those people whom we can help."

Trudie Chalder is recruiting for a new, larger trial of CBT. Children must be aged 11 to 18 years. Anyone interested can e-mail: sphatrc@iop.kcl.ac.uk