Optimists have a longer life-span than pessimists, researchers have concluded.

They found that people with a positive outlook live, on average, 19% longer than those who are miserable.

More than 1,100 patients attending the Mayo Clinic, in Minnesota, USA, between 1962 and 1965 completed a personality survey, which gave them an optimism ranking according to their views of the causes of events in their lives.

By looking at the patients 30 years later, the researchers discovered that those who had been classified as optimists had a 19% higher chance of still being alive than the pessimists, reports the Mayo Clinic Proceedings.

'Common sense'

Psychiatrist at the clinic Dr Toshihiko Maruta said: "It confirmed our common sense belief. It tells us mind and body are linked and that attitude has an impact on the final outcome, death."

But he and his team could not say if this was due to happy people's immune systems being stronger directly because of their optimism.

The other option was that they were more likely to seek medical help when they become ill, they said.

Optimists were less likely to suffer depression and helplessness and were less fatalistic about their health chances.

Commenting on the report, Dr Martin Seligman, of the University of Pennsylvania department of psychology, said: "Now I believe we have converging and compelling evidence that optimists and pessimists differ markedly in how long they will live."

Pessimism was identifiable early and could be stabilised by therapy which changed the individual's thinking about bad events, he said.

Philip Tata, head of adult psychology at St Mary's Hospital, Paddington, in London, said: "Optimism and pessimism are more complex than people think. Most people think they are opposite ends of one scale, but you can actually have high levels of both at the same time.

"A lack of optimism, rather than a negative outlook, can be just as problematic. Having a reason to live rather than just seeing terrible things coming down the road at you is important."

He said the results of the Mayo Clinic research could be down to the common phenomenon of old people giving up hope when things went wrong in their lives, hastening death.