MANY perfectly healthy people will recognise the symptoms: reading about some illness only to be left with a nagging concern that they may be suffering it themselves.
But hypochondria among the worried well has reached new levels, psychologists are warning. Growing use of the internet has led to what they have termed "cyberchondria".
Researchers found that those who fear the unknown with regard to their health only find the condition worsens as they seek answers on the internet.
Searching websites to discover what is ailing individuals is becoming increasingly common.
A recent survey showed that millions of Britons seek answers online rather than visiting their doctor, prompting warnings that they were risking their health.
In the latest study, Dr Thomas Fergus, of Baylor University in Waco, Texas, said that fearing a catastrophic disease or injury, unfounded or not, can trigger worries about disability, job loss and potential medical bills.
That can lead to even more searching of the internet, obsessing, visits to doctors, unnecessary medical tests and distress, he said.
Cyberchondria could be more harmful than its traditional version, because of a glut of sometimes dubious material available at the click of a mouse, he added.
"If I am someone who does not like uncertainty, I may become more anxious, search further, monitor my body more, go to the doctor more frequently – and the more you search, the more you consider the possibilities," Fergus said.
"If I see a site about traumatic brain injuries and have difficulties tolerating uncertainty, I might be more likely to worry that is the cause of the bump on my head."
Following research showing that about eight in 10 American adults seek medical information on the internet, Fergus sampled 512 healthy people with an average age of 33 to analyse how it affected their anxiety.
In the study, published in the journal Cyberpsychology, Behaviour and Social Networking, he used several measures, including a scale on which respondents assessed such statements as "I always want to know what the future has in store for me," and "I spend most of my time worrying about my health". Two thirds of the participants were unmarried, just over half were women, about two thirds had at least a two-year degree and more than half worked at least 20 hours a week.
Fergus concluded that while fearing the worst about health was not new, some online medical information may be more disturbing than details contained in medical manuals that people consult, or obtain directly from a doctor.
He added: "When you look at a medical book, you might not see all the possibilities at once, but online you are presented with so many." – The Telegraph