Research carried out Bradford University Management Centre found that people who think in black and white terms tend to become emotionally upset and often very angry whenever their values or goals are opposed or thwarted.

Such emotional disturbance makes them less able to deal with problems, manage relationships, and, if protracted, may result in longer term mental and physical health problems, they say.

The researchers, Dr Alistair Ostell and Dr Susan Oakland, interviewed 80 headteachers and classified them as 'absolutist' or 'non-absolutist' in the ways they handled two work problems. Their work is published in the British Journal of Medical Psychology.

Absolutist thinkers see things in a black or white way, evaluating events and the views and actions of others as right or wrong, acceptable or unacceptable.

In contrast, non-absolutist thinkers may have clear, firmly-held views, but are not moralistic, tend to see 'shades of grey' and are generally willing to tolerate and negotiate over differences.

Absolutist headteachers experienced their job demands as less pleasant, and perceived themselves as less effective at managing their emotions and handling problems.

They also demonstrated poorer mental and physical health.

The more open-minded and flexible approach of non-absolutist heads made problem-solving easier and promoted better health.

Anger and fury

Dr Ostell said: "These findings are not peculiar to the teaching profession, but apply equally to other professions and occupational groups."

He said the problem with absolutist thinkers was that as well has having firmly held opinions, they tended to act with fury, anger or resentment when those opinions were challenged, and to seek to exact retribution when they felt they had been wronged.

"In a lot of situations you cannot express an opinion overtly, and so you retain that anger within yourself," said Dr Ostell.

"You think about it, ruminate on it, and imagine what you would really like to do to those people if only you had a chance.

"That winds you up, eventually to such an extent that you cannot think clearly about the situation and if that situation involves another person it can lead to the disruption of that relationship."

Dr Ostell said that absolutist behaviour could also lead to physical problems such as tiredness.

Retained anger had also been linked to an increased level of the hormone cortisol in the bloodstream.

Cortisol suppresses the immune system and reduces the body's defence against infection.

Many scientists also believe that anger raised levels of another hormone, noradrenalin which constricts the blood vessels, leading to increased blood pressure.