I'M AFRAID that this newspaper is as much to blame as all the others. Last week The Independent on Sunday ran a huge piece on the "Fear and gloom inhabit(ing) Britain's high streets and workplaces".

To me the bad news is not that we're all going to be ruined in the global financial crisis, but that in the process our negative thinking is going to ruin our health. There is plenty of scientific evidence to show that an optimistic outlook is better for physical and mental health, while bad thinking makes us unconfident, out of control and fearful. Even the article said that "we may have talked ourselves into" it.

It wouldn't have happened if the stock-markets were run by self-help gurus. They have long insisted that you are what you think and so you need to think positively.

Science is cautiously, but increasingly, supportive of this view. "The placebo effect is a very clear demonstration that positive thinking can have biochemical effect," says psychologist Dr Martin Bamber, Head of York Cognitive and Behavioural Therapy and specialist in Psychoneuroimmunology. "In one famous study done on outpatients receiving chemotherapy, 70 per cent were actually put on a placebo but all were told they were being given chemotherapy and would experience hair loss. The ones on the placebo did indeed experience hair loss."

Negative attitudes have been linked with a depressed immune system, viruses, and with increased blood pressure, heart disease and possibly even cancer.

"I knew," says pessimist Jane, 31, "that I would have a difficult pregnancy. I fell pregnant the same time as a friend. She always thinks everything is going it be wonderful. I was constantly sick and spotty. I had swollen feet, an 18-hour labour and stitches. She blossomed immediately, looked gorgeous, gave birth in water in three hours, saying it was the most amazing experience of her life. Typical."

In the Winnie-the-Pooh psychological map, the extreme ends of optimism and pessimism are of course Eyore and Tigger. And just as it is unhealthy to spend your time in Eyore's gloomy place, so it is not good to be ridiculously bouncy all the time. It gets one into scrapes. Tiggers are huge risk takers because they assume everything will be great.

Optimists feel that they are in control of their lives. They feel that what they do makes a difference. Pessimists believe that their jobs are insecure and even if they were secure, they would still be pointless. They believe that the world is a bad place. And then they get a virus that proves it.

So how do you move from Eyore to, say, rabbit (busy and gregarious) or Christopher Robin (benevolent authority)? "We get the patient to challenge their negative assumptions," says Dr Bamber. "A pessimistic person will say their week was 'terrible'. But when you look at it in more detail there will probably only be a couple of bad incidents."

So, looking objectively, are you guilty (there's a pessimistic word-choice) of any of the following:

1) finding constant evidence to confirm a pessimistic world view;

2) minimising personal successes;

3) jumping to conclusions about other people, "I know what she really means ...";

4) having an all-or-nothing approach - if I am not completely successful I am a failure.

Try questioning your negative thoughts on a daily basis. One scientist estimated that 80 per cent of our thoughts are negative yet 80 per cent of our lives are not awful.

Ironically, I find that a totally bleak outlook starts making one more cheerful. It's attitude, not circumstances, that count. As the most optimistic person I know said, bafflingly, of her recent double bereavement: "I think it's actually a good thing because it makes you so much more appreciative of everyday life."