Chronically-stressed children are far more likely to have asthma attacks than less-stressed children, experts have found.

The link between stressful lives and wheeziness could result from damage to the immune system, they say.

The research, carried out at the University of Helsinki in Finland, is published in the Lancet medical journal.

Stress has already been blamed in adults for contributing to heart disease and even cancer and in children to appendicitis or rheumatoid arthritis.

And even the children of excessively anxious parents have been found to be more likely to develop asthma.

The researchers followed a group of asthma 90 child patients in Glasgow, aged between six and 13 for 18 months, noting when they had attacks, and finding out about the stressful events in their lives.

Poor housing

These included living in poor housing, having a parent or relative with a chronic mental or physical illness, the death of a granparent, experiencing family break-ups or being bullied at school.

The effect of a single "severe event" was delayed - but there was more than one and a half times the normal risk of an asthma attack in the following four weeks.

But when there were "severe events", but the child was also considered to be suffering from ongoing stress, the risk rose sharply.

These children were almost three times more likely to have asthma attacks.

All these risks were even worse for female children, those who normally had three or more attacks within the previous six months.

Parental smoking, unsurprisingly, also made the situation worse.

The researchers wrote that an earlier study of schoolchildren had found that between 80% and 85% of attacks were generally associated with infections in the upper respiratory passages.

However, they added: "Stress may well be a major factor in increasing susceptability to viral infections in the first place.

"These studies make a strong case for psychosocial stress increasing the risk of somatic diseases, particularly those that result from the weakening of the body's natural defence mechanisms."