Cyberchondria: The perils of internet self-diagnosis

Catherine was worried. For weeks she had been experiencing twitching in muscles all over her body. So, she did what millions of us would do: she Googled "muscle twitching". Do the search yourself to see why Catherine's worry quickly turned to terror. Among the results are a page on a university website about Creutzfeldt-Jakob disease (CJD), the incurable and fatal brain disease (which lists "muscle twitching" as a symptom), and a site about amyotrophic lateral sclerosis (ALS), another rare and fatal brain condition, also known as Lou Gehrig's disease.

Next stop: Catherine's doctor. But just as quickly as she beat a path to his door, he ruled out anything serious – after all, the chances of contracting CJD or ALS are vanishingly small. Instead, he diagnosed benign fasciculation syndrome (BFS), a medical name for a number of non-threatening symptoms that include twitching. But that wasn't enough for Catherine, who Googled "BFS" when the shakes got worse. She ended up on a forum at the site AboutBFS.com.

"New member ... terrified ... mouth/speech problems. PLEASE help", she posted last month. "I have been living life as if I was going to die in 18 months ... I feel like everyone thinks I'm crazy." But Catherine is no more crazy than she is terminally ill. She is, however, a "cyberchondriac", a term that describes a growing number of otherwise rational internet users who, when they present their symptoms to "Dr Google", latch on to the worst "diagnosis" thrown back at them.

Cyberchondria has been around for almost a decade, but a recent study is the first to systematically investigate it. Eric Horvitz and Ryen White, scientists at Microsoft's research division, analysed the internet behaviour of a million surfers around the world, and carried out a survey of more than 500 Microsoft employees, to discover how the internet is giving many of us an acute case of the heebie-jeebies.

Let's take brain tumours as an example. They are mercifully rare, developing in fewer than one in 50,000 people (0.002 per cent of us). Yet Horvitz and White's research shows that 25 per cent of the documents thrown up by a web search for "headache" points to a brain tumour as a possible cause. ALS, which is the form of motor neurone disease (MND) from which Stephen Hawking suffers, is similarly rare; MND affects fewer than one in every 14,000 people (0.007 per cent of us). But again, as Catherine found, the proportion of websites listing it as a cause of twitching is significantly higher.

"The problem starts with bias," says Horvitz, who also has a medical degree. "Nobody is excited to write about caffeine withdrawal and its role in headaches, but brain tumours – that's much more interesting. Search engines aren't savvy about this bias – they are programmed to generate results relevant to the query, not the person making it." Apparently unaware of the disproportionate level of attention given to scary diseases, people frequently relate search rankings with likelihood; if a search for muscle twitching reveals three results near the top of the page about ALS, then, as Horvitz says: "It's, 'Oh my God, these twitches mean I've got motor neurone disease – get me a wheelchair!'."

Why are so many of us so willing to believe the skewed result of web searches? One problem is laziness. A recent American study by the Pew Internet Project revealed that while eight in 10 of us use the internet to look for information about our health, about the same proportion – 75 per cent – do not check the source of that information or the date it was created. The rest comes down to psychology. Horvitz points to a famous fallacy known as "base rate neglect", where evidence makes people believe something is relatively likely to happen, despite the real chances being very low. "If a healthy person under 35 has chest pain, it is unlikely to be related to the heart, but because there is so much on the web linking the two, they forget the low background probability."

A similar effect playing on the minds of cyberchondriacs is something called "availability bias", which happens when people make predictions of likelihood based largely on what comes to mind. A classic example is the smoker who thinks they're safe "because my granny smoked 20 a day and lived to 96". Likewise, the net surfer who sees 100 results for ALS lets that skew their prediction of their own risk. "The same thing happened before the internet," Horvitz adds. "I remember getting worried when I was studying medicine. According to one study, up to 75 per cent of first- and second-year medical students end up thinking they have one significant yet imaginary disease based on what they're learning – some call it 'medical school-itis'. To some extent, the internet is making first- year medical students of us all. The problem is that often the information isn't as good."

Surely the only cure for cyberchondria is to steer well clear of the internet? Not according to Pauline Brimblecombe, a GP who works near Cambridge. She believes the internet has made patients "more interested in their own health and therefore more likely to look after themselves". She adds: "If my patients Google something and come rushing in with bits of paper, at least I know what they're worried about and can reassure them." Horvitz, too, believes in the power of the web. "It's an extraordinary resource for healthcare information," he says. "We're talking about a stone with a rough edge here, not a fatal flaw."

One man trying to polish that stone is John Voorhis, an IT consultant from New Jersey. When he developed muscle twitches like Catherine's, he was also scared. But, unlike Catherine, Voorhis was reassured by his doctor, who also diagnosed him with BFS. Then, alarmed by the lack of information about his condition – and the tsunami of online horror stories – he launched AboutBFS.com, the site that allayed Catherine's fears. "A lot of people come to the site thinking they have ALS," Voorhis says. "Now they find a community of people to reassure them. I can't count the number of times I've had emails from people saying the site has saved their marriage or even their life."

Voorhis is helping one group of cyberchondriacs, but a Swiss organisation is trying to reach them all. The Health on the Net Foundation (HON) started life in 1995 with a meeting of 60 scientists in Geneva. "They realised very early on that the internet would be used not only by researchers and scientists but also the general public," says Celia Boyer, HON's executive director. "They also identified that due to the nature of the web – anyone can put information online – it could be a dangerous place to get health information."

HON has set up a code of conduct, which requires the 6,500 sites that have signed up to it to display information responsibly and inform readers about its purpose and source. It also runs Medhunt, a search engine that pools results from trusted sites. "We are also developing the next generation of search engine," Boyer adds. "We want to create a kind of filter you can add to Google or other sites that only presents results from approved websites."

Horvitz goes one step further and prescribes smart search engines that realise when someone is tapping in symptoms, automatically switching to a "diagnostic mode" in which users are asked their age and other information to provide results based on likelihood rather than simply relevance. But until "Dr Google" wises up, Horvitz says the responsibility to reassure the growing number of cyberchondriacs panicking at their keyboards lies with GPs. "Doctors need to work with patients and realise they are going to go to the web before they come in," he says. "They need to provide guidance on good websites and put themselves in patients' shoes so they know what's out there – good or bad."

Medical sites: Who to trust

Medhunt

Run by the Health on the Net Foundation, this search engine pools results from websites that comply with its strict code of conduct. www.hon.ch/MedHunt

NHS Direct

Choose your symptoms from an A-Z list or pick a body part to narrow the search for a possible cause. The site will often direct you to your GP. www.selfhelpguide.nhs.uk

Patient UK

Comprehensive source of information run by doctors. Read leaflets, find support or even book appointments and order repeat prescriptions. www.patient.co.uk

WebMD

American site with exhaustive content designed to help you manage your health and find help, plus a smart symptom checker. www.webmd.com