People can have severe symptoms when they are perfectly healthy
This week it emerged that some three million people in the UK suffer from imaginary food intolerances. Are we really a nation of hypochondriacs?
The "worried well", it would appear, are everywhere: an estimated one in four GP appointments is now taken up by someone who has absolutely nothing wrong with them.
But while the popular view of the hypochondriac is the patient who instantly declares a cold to be flu - those who suffer from health anxiety, as it is now more sympathetically dubbed, rarely concern themselves with such mundane conditions.
For those with health anxiety every twinge can be the latest symptom of a terminal disease. Anxiety exacerbates any ache they have so that their pain becomes real - and potentially debilitating.
Hundreds of thousands of people in the UK suffer from such acute anxiety about their health that they are unable to work.
"They may be at the extreme end of the spectrum, but this is a problem for many people and it has to be seen as condition in itself," says Professor Paul Salkovskis, the director of the Maudsley Hospital Centre for Anxiety Disorders and Trauma.
"Their suffering is genuine, and their pain often greater than if something really was wrong with them."
Hypochondriasis is not a modern phenomenon.
The word is Greek, and literally means "beneath the breast bone cartilage".
Adolf Hitler - took countless pills
Tennessee Williams - health fears led to alcohol and drug dependence
Lord Byron - wrote and worried about being thirsty
Howard Hughes - became recluse over fear of germs
Early physicians apparently found that many patients who claimed intermittent pain in this area often transpired to have little wrong with them.
Moliere poked fun at hypochondriacs in his Le Malade Imaginaire of 1673 while the main character in Jerome K Jerome's Three Men in a Boat of 1889 finds while researching his illness in the British Library that he has every condition going aside from "housemaid's knee".
But while those with health anxiety tendencies in the past had limited sources to feed their paranoia, symptoms can now be looked up on the internet as rapidly as they appear, while adverts call out from magazines and newspapers for "wellness checks" and body scans.
This is fuelling anxiety, according to Dr Mike Fitzpatrick, A London GP.
"But you can't just blame the media and the internet," he says.
"People are becoming ever more introverted and self-preoccupied, and consequently they do worry much more about their bodies. Many of the government drives around health awareness sometimes only seem to make that worse."
But opinion is divided as to whether the ranks of the worried well are really swelling. There is little evidence to suggest that numbers are rising, even if the anxious individual may have more ways to fuel his worries.
But the discussion about health anxiety does take place within an NHS in which resources are increasingly tight.
There are no figures on how much hypochondriasis costs the health service each year, in part because it is almost impossible to draw a line between where rational anxiety passes into the irrational.
But it is thought vast amounts of money are involved, and yet Professor Salkovskis suggests the NHS is reluctant to engage with the problem.
Currently there are no guidelines to deal with the condition.
Patients are either repeatedly turned away by their GP, or sent for "reassurance" scans to prove to them that nothing is wrong with them.
But such tests, it is argued, rarely provide the patient with the reassurance he or she needs - leading to further demands for more tests and examinations - or merely tying them over till the next worry emerges.
Cognitive Behavioural Therapy, a form of psychotherapy which tries to understand and modify behaviour, is one option, but it rarely offered or publicly funded.
"But it ultimately pays for itself," says Professor Salkovskis.
"After a year you have people who might have been visiting their doctor every other day turning up once every six months - which is exactly what you want - the national average".
"People start to understand no one can tell them definitively 'you do not have cancer', but they start being able to live with that."