Why, when medicine has made so many advances, do we worry so much about our health? Introducing a three-part series, Roy Porter suggests that conflicting advice causes our anxiety
The Chancellor never stops telling us things are getting better; and with low inflation, low interest rates and falling unemployment, that may be true. Yet no one feels good, the public brow is furrowed. And it's not just our view of the economy, it's also the way we're perceiving our health.

Yet according to standard benchmarks, we've never had it so healthy. Longevity in this country continues to rise: a woman can now expect to live to 79, eight years longer than in 1950 (the male equivalent figures are 73 and 66). Break down the figures a bit and you find other encouraging signs: in 1950, there were 26,000 infant deaths a year, today there are 5,000.

Deaths from infectious diseases nearly halved between 1970 and 1992, and those from diseases of the circulatory and the respiratory system went down by about a third; between 1971 and 1991 deaths from stroke dropped by 40 per cent, coronary heart disease deaths by 19 per cent.

The list goes on and in myriad ways, medicine continues to advance, new treatments spread and surgery works marvels. So how is it that we're so stressed about our health and its hazards? Why do our bodies feel ever more vulnerable? When a few cases of CJD occur - or for that matter, when once in a while a teenager dies after taking Ecstasy - why is there such alarm, given that the tally of cases, and therefore the individual risk, is quite minuscule?

Why is there that all-pervasive sense that our well-being is imperilled by "threats" from all around, from the air we breathe to our daily pinta?

Who would have believed 20 years ago that those who see themselves as taking their health obligations seriously would get hooked on bottled water? How is it that we're so much more agitated now about pollution than during those genuinely awful urban smogs of the Fifties, when tens of thousands died each winter of bronchitis as a direct consequence? What's come over us? Have we become a nation of hypochondriacs or health freaks, or have we all finally wised up?

It's important to get things into historical perspective. We're by no means the first generation to go down with this odd "doing better, feeling worse" syndrome. The 18th century was a time of peace, plenty, opportunity and prosperity - and even some medical breakthroughs (smallpox inoculation had just been introduced). Yet did the nation feel healthier?

Not a bit of it! The English gained international notoriety for their glowering depression - the spleen and vapours and the complaint that for the very first time got labelled "nerves". It was a paradox put into a nutshell by a canny Scottish physician, George Cheyne, who practised in Bath. He maintained there was a new disease afflicting the nervous system that he called the "English Malady".

What caused it? Well, partly it was "the Variableness of our Weather" but mainly, he declared, it was due to the "Fertility of our Soil, the Richness and Heaviness of our Food, the Wealth and Abundance of the Inhabitants (from their universal Trade)", and so forth. In short, it was a disease of civilisation, the price of prosperity. Affluence begat anxiety. Suffering was a symptom of success.

The psychology that sustained the Georgian feel-bad factor was brilliantly exposed by another spa physician, Thomas Beddoes, practising at fashionable Clifton, a man who fumed over the health antics of his posh patients from polite society. He said they had enough leisure to indulge themselves and grow self-absorbed; enough education to lap up the heaps of health advice filling the new magazines and the self-cure guides pouring off the presses; and enough sensibility to be hyper-suggestible.

It was, Beddoes griped, a sad reflection on human nature that the better- informed people grew, the more panicky they became about their health thus confirming Dr Cheyne's observation that it was never "slow thinkers" and "no thinkers" who got his English Malady but the intelligent.

It all sounds a bit like the situation in which we find ourselves today. So are our health cares and scares just the hysterical foibles of people who should know better?

In part, yes. Many of the so-called health threats are matters that we should shrug off and take in our stride. It really is a complete fantasy to think that our tap water has somehow suddenly become so perilous that any responsible person is forced to drink the bottled stuff.

But before we condemn "impressionable" people for being health-obsessed, such fears need to be put into context. We live in an cockpit of conflicting pressures. We are trapped in the rising expectations spiral. The media is endlessly beaming messages telling us we can, and should, be healthier, fitter, more youthful, beautiful, glamorous and sexy. And the way we're expected to do that is through self-help and looking after Number One - the philosophy (with respects to Norman Tebbitt) of "on your exercise bike".

All that well and good - up to a point. But the catch is that rising health expectations can have no imaginable ceiling. As the sad case of Michael Jackson shows, achieving the perfect face or body is a will-of- the-wisp; absolute health eludes our grasp, and in the long run we're all dead. It's all very well to bid people to take their health into their own hands. But that requires a climate of trust. They must feel, for one thing, that it's possible to know what is right, sound and healthy. But the truth is we're tossed on a sea of conflicting advice: one day alcohol is bad for you, so you'd better cut it out; the next the authorities say you're meant to swill several glasses of wine a day for your heart. perhaps butter will prove better than lab-made margarine. And what of British beef? Who knows?

So the irony of science, as the BSE scare shows, is that its vaunted expertise spreads not confidence but qualms. In such circumstances any government with an ounce of sense would go out of its way to provide heavy- duty health reassurance. But NHS cuts,and this Government's refusal to accept responsibility for anything, means that no one's sure any longer whether the local casualty department is still open, where the nearest hospital bed will be if you have an accident, or whether the beggar on the street is just a harmless layabout or a homicidal maniac under "community care".

There is an air of mistrust abroad in which no one feels sure anything is safe (when Mr Gummer declared British beef was safe, 10,000 people reputedly turned vegetarian).

Maybe it's all a cunning ploy to keep us on our toes: no strain, no gain. Any evolutionist will tell you that anxiety is the best defence mechanism: the more edgy we get, the fitter we'll be. But is the survival of the hyper-anxious really the recipe we want?

The writer is a medical historian at the Wellcome Institute for the History of Medicine.