Chronic fatigue syndrome (CFS) makes people angry. Not so much the condition itself, which is associated with diffuse body pain, persistent tiredness and loss of concentration, but the science around it. After an American team announced last year that they had found a novel virus in 68 of 101 CFS patients, a UK team just reported that they failed to find the virus in any of the 186 patients they studied. Knives have already been drawn in the latest round of a long-running battle.

To understand why this is such an emotive issue, you need to get a handle on some key issues.

The first is that there is a heated debate as to the causes of the condition. On one pole of the debate is a group, largely of people affected by the condition, who believe that the condition is entirely caused by a biological disruption to the body, most likely an unidentified viral infection. On the other, is a group, largely consisting of researchers, who believe that there is a significant psychological component to the illness.

This is, of course, a bit of a simplification, but it broadly captures the two main sides of the debate and if you’re not familiar with how high feelings run, let me give you an example. I was contacted by one CFS researcher wanting a copy of a paper I wrote on extreme communities because their family was under police protection following death threats, subsequent to a public suggestion that psychology might play a part in the condition.

The emotion is fuelled by the common, insidious but wrong-headed notion that any condition that is influenced by mental states is not a ‘real illness’ and the widespread prejudice that individuals are more to blame for psychological problems because psychology is perceived as being just a matter of ‘changing your mind’.

There is a mountain of research to show that both of these claims are plainly ridiculous and psychology is likely important in all illness, but perhaps the clearest example is the placebo effect. You can’t just ‘decide’ to better but the placebo effect has been shown to improve the symptoms of almost any illness your care to think of, albeit to differing degrees.

But people affected by CFS are often on the sharp end of these prejudices and it is not uncommon that they have had the experience of someone telling them they are ‘putting it on’ or ‘aren’t trying hard enough’. When you are disabled to the point of immobilisation, this is pretty hard to take.

So it is not surprising that many are drawn to the exclusive ‘viral infection’ explanation, because it proves the idiots wrong, even if it does so using the opposite side of the same coin – prejudice about what constitute a ‘real illness’.

Proponents of the idea that the condition is influenced by psychology, including beliefs about its effects, behaviour patterns and perceptions of how the body is reacting, note that numerous controlled studies have found that a psychological approach, in the form of a cognitive behavioural therapy (CBT), is one of the most effective, if not the most effective treatment. Despite this, it is often rated as one of the least preferred among patients groups.

Into this hot button debate steps an American team who found evidence for the little understood retrovirus XMRV in about two thirds of patients with CFS. Proponents of the ‘viral theory’ rejoiced and the study made headline news around the world.

Considering the potential importance of the findings, a UK team then attempted to see if they could detect XMRV in British CFS patients. It has widely been described as a ‘replication’ of the original study in the media, but it really isn’t, as the team used a different, although still reliable ways of looking for the virus, while attempting to make improvements in lab management to reduce the chances of cross contamination and detecting false positives.

They found nothing in any of the 186 patients they studied. No sign of the virus at all. The research was published in PLoS One and if you want a flavor of the feeling the research has generated, take a look at the ratings and comments on the article since it was published earlier today. You can almost feel the anger simmering through.

From an outsider’s perspective, it’s interesting to see how CFS is considered by many to be a single condition that must have a single cause. But in reality, the diagnosis is just made on a collection of symptoms – tiredness, pain, impaired mental abilities and so on.

These symptoms are interesting because they occur in a whole range of conditions: in diabetes, after concussion, after a viral infection, after any of stroke, brain injury or Parkinson’s disease, alongside a range of mental illnesses, and so on.

In other words, there is unlikely to be a single cause for CFS, because the same symptoms can be caused by any number of underlying problems. The reason that CFS isn’t diagnosed in all these other cases is because it is a diagnosis of exclusion – in other words, by definition, if you can’t find a clear cause, the symptoms are labelled as CFS. However, it doesn’t follow that all current cases of CFS will therefore by accounted by a single, currently unknown, problem.

I wouldn’t be surprised if some cases of CFS are triggered by an unknown viral infection, but to think that this is the sole explanation is likely to be missing the bigger picture.

Similarly, to deny a psychological component to any medical condition risks denying a useful tool to help those who need it most. As an illustration, surgeons now widely recognise that psychological factors are essential to the long-term success of a transplant.

You would be hard pressed to find a more ‘physical’ condition and yet psychology plays a key role. But to promote the importance of thinking about the role of our own minds in how disability affects us, be with transplants or CFS, we need to fight the prejudice associated with mental explanations.

Link to PubMed entry for US study on the XMRV virus and CFS.

Link to UK CFS study in PLoS One.

Full disclosure: I’m an unpaid member of the PLoS One editorial board.