Personality types are the sort of subject you might glance at while flicking through a magazine in the GP's waiting room. Pretty frivolous stuff, you perhaps think.

However, new research suggests our personality traits are more significant than previously thought, and can play a key role in future health.

It's long been reported that people with socalled Type A personalities - hostile, highly competitive and impatient - are more prone to heart problems.

But now researchers are increasingly finding that a wider range of personalities and traits are linked to a host of medical problems, from stomach ulcers and viral infections to Parkinson's disease.

Quite how personality then triggers increased vulnerability or resistance to disease is unknown, although there are various theories. Here we look at the personalities and their ailments - and what the scientists believe is going on.

IMPULSIVE

You might expect impulsive types to be at risk from accidents but, in fact, their big health danger is stomach ulcers. Researchers at the Finnish Institute of Occupational Health studied more than 4,000 people and found that those who had an impulsive personality were 2.4 times more at risk.

It's thought that impulsive people tend to respond to stress with higher than normal rates of acid production, triggering peptic ulcers.

Research at the University of Wales has also shown that impulsiveness is associated with poorer control over eating.

CHEERFUL

One of the most surprising findings is that cheerful people are more likely to die early.

'Children who were rated by their parents and teachers as more cheerful, and as having a sense of humour, died earlier in adulthood than those who were less cheerful,' say University of California researchers. 'Contrary to expectation, cheerfulness and sense of humour were inversely related to longevity.'

One theory is that cheerful people underestimate life's dangers and may also be more likely to have difficulty coping when things don't go as anticipated.

ANXIOUS

People with anxiety disorders are three times more likely to be treated for high blood pressure. A study from Northern Arizona University found stress hormones may be the reason.

Meanwhile, women with phobic anxieties, such as fear of heights, were at higher risk of heart disease, high blood pressure and cholesterol. Although behavioural differences - like a greater tendency to smoke among people with anxiety - go some way to explaining why this happens, they do not explain it all.

Here's something else to worry about: a University of Antwerp study found that within ten years of heart treatment, 27 per cent of anxious types were dead, compared to 7 per cent of others.

AGGRESSIVE

Hostile types are prone to a range of serious health conditions, and there is plenty of research to back this up.

People who suffer from artherosclerosis - furred up arteries - are more likely to have hostile personalities, according to a Scottish study based on almost 2,000 men and women.

An American study showed that aggressive types are at greater risk of chronic inflammation throughout the body, which is linked to a number of diseases including heart disease (inflammation is involved in the build-up of fatty deposits in the inner lining of the arteries).

This could be because this personality type has higher levels of an immune system protein linked to inflammation.

Another theory is that hostile people respond more quickly and strongly to stress, both mentally and physiologically, increasing blood pressure and heart rate which results in more wear and tear on the cardiovascular system.

Angry types also take longer to heal. Researchers at Ohio State University created small wounds on the arms of healthy people, and after four days, only 30 per cent of the angry patients' wounds had healed, compared to 70 per cent of placid patients.

Aggressive types are also at higher risk for recurrent bouts of severe depression, according to another American study.

SHY

Socially inhibited people are more vulnerable to viral infections, suggests research from the University of California.

In animal studies, scientists found that gregarious types had more active protective lymph nodes than shy types. Lymph nodes are part of the body's immune system and help to destroy infectious germs, such as viruses like the common cold virus and bacteria.

OPTIMISTIC

People who always look on the bright side live, on average, 7.5 years longer than those who take a gloomier view, according to work at the University of California.

And the risk of dying early from any disease is 55 per cent lower for optimists, say researchers at Wageningen University in the Netherlands who followed 1,000 people.

One theory is that optimism may increase the will to live, while another is that greater sociability plays a role; these in turn may lower levels of the stress hormone cortisol.

Researchers at Carnegie Mellon University in Pittsburgh say that optimism boosts the immune system and protects from psychological stress.

An American study showed that over a 30-year period, optimists had fewer disabilities and less chronic pain.

The authors suggest that these people have poorly regulated stress hormones, meaning their hearts beat faster, blood pressure rises and blood vessels tighten - all bad for the cardiovascular system. Such types may also have more active immune systems, and therefore more inflammation, which results in damage to blood vessels. 

CONSCIENTIOUS

This is the personality trait most associated with long life, according to a University of California study. It has as significant an effect on longevity as maintaining healthy blood pressure and cholesterol levels, research from Nottingham University suggests.

It's thought conscientious people avoid risk and are more likely to adopt and maintain healthy behaviours.

NEUROTIC

If being a neurotic type wasn't hard work enough, it's also associated with asthma, headaches, stomach ulcers and heart disease, according to a University of California study.

It's suggested that neurotic types often employ less effective coping strategies, with lots of selfblame and hostility, rather than seeking help and support.

They therefore may become more stressed, resulting in a less effective immune system and greater vulnerability to disease. Another theory is that neurotics are more likely to be depressed, and depression lowers the immune system.

EXTROVERT

Like optimists, they are less likely to get heart disease, according to a Milan University study. Italian researchers found that the biggest extroverts were 15 per cent less likely to get disease.

They are also more likely to recover quickly from disease, and less prone to infections.
One theory is that they have more effective coping strategies so fewer stress hormones. They may also be more likely to seek medical help for symptoms.

But one downside is that, according to research at Yamagata University School of Medicine in Japan, they are more likely to be obese than neurotics.

Theories range from behavioural differences, with extroverts more likely to be sociable and therefore eat more, to genes.

PESSIMISTIC

Those who always expect the worst will find that when it comes to health, they're right: pessimists have a 19 per cent increased risk of dying early compared to optimists.

Researchers in America have also found that people who have high levels of pessimism and anxiety have an increased risk of developing Parkinson's disease decades later.

'What we have shown for the first time is that there's a link between an anxious or pessimistic personality and the future development of Parkinson's,' says neurologist Dr James Bower from the Mayo Clinic.

'What we didn't find is the explanation for that link. It remains unclear whether anxiety and pessimism are risk factors for Parkinson's disease, or are linked to Parkinson's disease via common risk factors or a common genetic predisposition.'

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