Doctors love to use initials. Patients' notes are littered with them: FLK, for funny looking kid or NFN, for Normal for Norfolk. But now two psychologists have come up with a new set - ICI. It has nothing to do with the chemical company, but stands for Invisible Chronic Illness.

Cynics may say that life is one long ICI, indeed the English poet Abraham Cowley said in the 17th century that 'Life is an incurable Disease', but the illnesses to which these psychologists refer are more specific. They include multiple sclerosis, irritable bowel syndrome, endometriosis, lupus erythematosus, Crohn's disease and premenstrual syndrome - an apparent ragbag of conditions affecting everything from the digestive tract to the reproductive system.

Although at first these illnesses seem to have nothing in common, on closer inspection, they have certain similarities, the most important being that, if you suffer from one of them, you often look well while feeling like death. Result? Little sympathy or understanding from those around you.

Two other properties characterise them. In many cases, diagnosis takes a long time because the signs do not immediately present a clear picture. They are marked by remissions and relapses, so that patients have to live with a great deal of uncertainty. Some ICIs, such as irritable bowel syndrome, are also not easy to discuss socially.

Doctors may not find the label useful, but patients with ICIs, seem to. 'I am thrilled that someone has given recognition to what can be a big problem,' says Moira Lazarus, a businesswoman from north London. 'I usually look fine, so even friends who know I have an illness do not ask me how I am or express any sympathy.'

Moira suffers from a rare condition, known as over-active mast cell syndrome, in which an outside stimulus, such as exercise or alcohol, sets off a massive allergic reaction in her body, resulting in rapid heartbeat, abdominal pain, a need to open her bowels, bursting of the small blood vessels in the eyes and, sometimes, loss of consciousness.

At first doctors thought she had epilepsy, but after two years, specialists at the Hammersmith Hospital, west London, tracked down what it was and now prescribe regular anti-histamine tablets as a preventive measure. These appear to weaken the attacks.

She is hurt by the reaction of friends, many of whom seem to consider her condition a psychological one. One said: 'So in your mother's day, doctors gave patients Ativan (a tranquilliser); now they give you anti-histamines.'

The two psychologists, Paul J Donoghue and Mary E Siegel, who have coined the new term, practice in Stamford, Connecticut, and spell out what it means in a new book*, published last week.

Both authors suffer from such illnesses themselves, Dr Donoghue from intestinal problems and sleep disruption, and Dr Siegel from multiple sclerosis. 'In my case, it took four years to diagnose multiple sclerosis, so I understand what it is like for people to visit numerous doctors and go through this interminable search for a diagnosis,' she says, adding that the illnesses attack the self-esteem more than many more dramatic, visible disorders, 'because those illnesses have a support system. They are recognised by society, families and friends and produce chocolates, flowers and so on'.

Dr Donoghue explained: 'These illnesses are so baffling. One moment you feel well and the next you feel terribly sick. One moment, you feel like a hypocrite and feel you do not deserve your disabled sticker or social security; and a week later you feel so sick you want to die.'

One person, who recognises some of these points is 28-year-old Lorraine Hudson, who lives in Somers Town, central London. She has multiple sclerosis. Although she has suffered spells when she has not been able to walk and has had double vision, her illness is usually totally invisible. Consequently, she has sometimes encountered a lack of understanding. She is attending a government-sponsored computer course for the disabled, and surprisingly, found some suspicion there.

'It was when I last had symptoms. My legs were really painful, like a constant aching in the bones. I could not walk 50 yards, certainly not as far as the Tube station, and I was waiting for my disabled sticker for my car from Westminster Council. The college was having to pay for taxis for me to get to the course, but it was clear it was not going to be for long, because my sticker was due to arrive soon.

'The course organiser said to me: 'Couldn't you try walking?' It really got to me. I felt she was challenging my honesty and suggesting I was lazy. The real problem was that I did not look ill. People really cannot understand it if you look well. If I feel all right, I catch the bus into college, because it is good for me psychologically, but I know when I cannot manage it.

'I was also getting out of my car once, and a man and asked me what my disabled sticker was for. I told him and he said: 'But you are not disabled.' I explained I had multiple sclerosis and, fortunately, he shut up.

'Things are uncertain with MS. I am half-expecting some symptoms to appear any time now, because I have been well for three months and they seem to strike at three-monthly intervals. But I feel I have come to terms with the disease, partly through having a very understanding partner and partly because I had some excellent counselling near the beginning with someone from the MS Society.'

The book gives advice about coping mechanisms and how to challenge negative thoughts, but the authors admit that some sufferers need professional help.

Unfortunately, relatively little psychological help is available on the NHS. According to Dr Stephen Wright, a clinical psychologist at Leicester General Hospital, with a special interest in chronic illness (particularly chronic pain and kidney failure), there is a shortage of clinical psychologists who deal with physical health. 'Britain has a bit of catching up to do. The evidence shows that psychological approaches can be very effective, a conclusion borne out by the fact that psychological approaches are popular in the US, where there is a free market.

'People with chronic illness get fed up with being told that they just have to live with their problem, without being given any guidance on how to do so. Often their problem is exacerbated by the fact that it is invisible and no one can see that they are suffering.

'Some patients say to me that they would almost like to walk round with a meter on their forehead displaying how much pain they are in, so that people would understand.'

Dr Wright uses a range of techniques to help people with chronic illness, including advice on relaxation skills and how to pace activities and reduce anxiety.

Both Dr Donoghue and Dr Siegel stress the need for patients to live in the present. 'Unless the ICI patient is living in the present, during an exacerbation, he will project a lifetime of agony into the future,' the book says. It also quotes Max Ehrmann's Desiderata: 'Do not distress yourself with imaginings. Many fears are born of fatigue and loneliness.'

'Sick and Tired of Feeling Sick and Tired', W W Norton, pounds 8.95.

(Photograph omitted)