Scientists at Oxford University have pioneered the world's first test for accurately measuring stress. A simple blood sample could be used to select people for the right jobs, help drivers know when to take a break, monitor stress at work and diagnose those in need of medical help.

The Oxford scientists, headed by a professor of zoology, have taken out patents to protect the technology and are seeking commercial partners. They have so far successfully used it to test their own stress levels while driving, and have measured stress in wild animals.

Stress has become an epidemic in the past 20 years, with research suggesting that more than half of the population have a problem at any one time. It is thought to have overtaken backache as a leading reason for people taking time off work. Too much stress can lead to health problems, from ulcers to heart disease.

But there has not, until now, been a precise scientific way of accurately measuring it. Questionnaires, audits and rough estimates have been used, and there have been attempts to measure hormones as an indicator of stress. The new test, which looks for changes in the immune system, uses a single drop of blood which is then exposed to a chemical that mimics bacteria. It causes a reaction in white blood cells, which identify it as a danger. The level of this response is used as a measure of stress levels. The theory is that if the individual is already under stress, the response will be reduced because some white blood cells would be otherwise occupied.

"It makes the white blood cells react as if they had been challenged by bacteria. If they have been challenged in the immediate past, they are less able to mount a coping response,'' said David Macdonald, professor of zoology at Oxford. The scientists, who are now looking for commercial partners to take the test to market, say that it provides instant, accurate results. In practice, stress levels of individuals would be measured against a generic baseline.

The test, which may be available as a hand-held, DIY device, could be used for animals as well as humans. "There is nothing else quite like it as far as we know, and we are at a very exciting point. I come from a background of wildlife, and there are all sorts of areas where it could be used. With humans, possible applications include jobs where it would be dangerous to have people who are stressed,'' said the professor.

"We carried out much of the work on blood samples from mammals in the wild which were thought to be under variously stressful conditions. When we compared them we found there were differences. It works for all mammals. We have used it on ourselves while we were in traffic jams, and there were changes in the levels.''

An outline document prepared for would-be commercial partners says potential uses include monitoring stress in the workplace, health screening for insurance, optimising stress relief when travelling and improving farming techniques. The document says: "For the first time, it will be possible to produce a quantitative measure of stress. To date, despite various rough indicators of stress, there has been no development of quantifiable and practical measures of stress for use in humans or animals.''

Scourge of modern life

Every day, 270,000 people take time off work for stress-related illnesses, making it the most common cause of absenteeism.

The condition costs the UK £1bn a year in lost productivity, NHS bills and other losses.

It has been linked to heart attacks and strokes, as well as acne, eczema and weakened immune systems.

The first personal-injury court case linked to stress at work was filed in 1997, and since then claims have soared.

Stress is a manifestation of the primeval "fight or flight" response to a potential threat or danger. When feeling stressed, the adrenal glands pump out the hormones cortisol and adrenaline to help the body cope.

Over short periods of time, stress is perfectly healthy and helps people to respond to problems and situations. But long-term, intense stress can cause severe health problems.

Scientists are still unclear why some people can cope better under pressure than others. Research has found that some people are more vulnerable to the effects of stress because a part of their brain called the cingulate cortex is smaller than average.

Another study pinpointed a gene that controls how well the brain uses serotonin, a chemical strongly linked to mood. People with a certain version of the 5-HTT gene responded better to traumatic events than those with a "shorter" version.

Like pain, stress can be a very subjective condition. Measurements of stress have traditionally relied on psychological assessments and physical symptoms such as stomach ulcers, but new research is leading to more sophisticated tests.

Maxine Frith