When a cause cannot be found


There is a philosophical problem within medicine: how to deal with causal complexity and variations. While existing methods are designed for large scale population data and sufficiently homogenous sub-groups, a number of medical conditions are characterised by their heterogenic and complex nature: low back pain (LBP), chronic fatigue syndrome (CFS), fibromyalgia syndrome (FMS), irritable bowel syndrome (IBS), tension-type headache (TTH), post-traumatic stress disorder (PTSD), and many others.

Typical for these conditions is that no common cause or even set of causes can be found. Instead of a clear-cut one-to-one relation between cause and effect, there is a whole range of symptoms and causes: biological, psychological and social factors. Thus, there is no clear psyche-soma division of symptoms. And since the symptoms of these conditions are complex, ambiguous and to a large degree overlapping, classification becomes a problem. But that is not all. In addition, each patient seems to have both a unique combination of symptoms and a unique expression of the condition.

Since no medical cause can be identified for these conditions, they are commonly referred to as medically unexplained symptoms (MUS).

This is not a small problem in medicine. By some estimates, such unexplained conditions amount to 30 percent of all symptoms reported to doctors, and they are linked to a 20-50% increase in outpatient costs and a 30% increase in hospitalisation. The US National Institutes of Health (NIH) identifies medically unexplained symptoms as the most common problem in medicine.

So why do I say that this a philosophical problem, and not, for instance, a methodological one? One reason is that any method designed to discover causes will also bring with it assumptions about what causation is. The methods of evidence based medicine, for instance, includes the Humean orthodox view of causation and probability. In observational studies we search for robust correlation, in RCTs we look for difference-making, and in populations studies we generate probabilistic evidence from statistical frequencies.

Not only do our methods include a notion of causation. They also come with ontological restrictions.

If we want to study genuine complexity, it’s not enough to replace the mono-causal model with a multi-causal one. The bio-psychosocial model was developed as a better alternative to the physiological model. But it still falls short because the methods are designed to study one causal factor at the time. We can perform separate studies for psychological, social and biological factors, and then add the results together. But this is to assume mereological composition: that wholes are sums of distinct parts which don’t interact. To deal with the patient as a unity thus becomes impossible. Instead, one can try to study parts of the problem separately: the irritable bowel, the anxiety, the pain, the fatigue. Genuine complexity cannot be studied in this way.

Heterogeneity and medical uniqueness are also features that require a certain ontology. Singularism about causation is the philosophical idea that causation happens in the concrete. Any statistical claim about what happens in a population will then only be a representation of many such individual causings. On a frequentist theory, in contrast, statistics generate probabilities. This is, basically, what evidence based medicine means: statistical evidence from population studies are applied directly to a patient. This means that each patient is treated as a statistical average, not as a unique individual.

We know that patients respond differently to the same treatments. At the same time, the methods and policies of evidence-based practice are premised on an assumption that the same treatment should be given to all. But what is the rationale for claiming that the same intervention in two different patients is even the same treatment?

My next planned research project, CAUSEHEALTH, is motivated by the idea that medically unexplained symptoms show a limitation of current medical thinking. Their challenging features of multifactorial causation (complexity), heterogeneity (context-sensitivity), medical uniqueness (singularity) and no clear psyche-soma division (holism), are all essential aspects of causation. Rather than being dismissed as marginal, therefore, these unexplained conditions should be taken as exemplary for understanding health and disease in general.

Further reading
As a pilot project to CAUSEHEALTH, the CauMed team wrote two papers: one on medically unexplained symptoms and one on causation and evidence based practice.


17 thoughts on “When a cause cannot be found

  1. Hi Rani,

    This is interesting, but I wonder to what extent altered notions of causality will help? The trouble with MUSs is that medicine can’t say anything general about why they happen, as you point out. Is your idea that with a different notion of causality, we would be able to say something general? Or that with a different notion of causality, we still wouldn’t be able to say anything general, but would no longer want to (perhaps because we now understand that that’s not possible, desirable, or both)?

    For me, MUSs do show something important, but not about causality per se: rather, they put pressure on the classification system that recognises them as diseases. A system based on causes fails for these diseases; but it’s not clear whether that’s a problem with the system, or with these particular diseases. That is to say, it forces us to decide whether classifying diseases by their causes is a bad idea, or whether it is still a good idea – in which case “low back pain” is a bit like grue.

    It will be interesting to see how these discussions develop in the project!


    • Hi Alex,

      Thanks for the comment! The idea is that existing research methods emphasise certain features that MUS resist: homogeneity, monocausality, causal determinism, robustness cross contexts and mereology. These features fit perfectly with the classical notion of causation. Alternatively, there is a dispositional notion of causation that embraces the features of MUS and take them to be essential aspects of causation: heterogeneity, causal complexity, context-sensitivity, singularism and genuine holism. If we expect causation to be like the classical concept, we won’t be able to find causes for MUS. But with the dispositional notion, we can approach MUS differently. If we expect medical uniqueness and genuine complexity, we will see that we cannot use research methods that study same cause, same effect on population level.

      Did this make more sense?


      • No worries. But I I don’t understand how the comment fits. My blog post is about how the relationship between scientific methods and philosophical theories of causation affects our search for causes in medicine.

      • Because a complex, heterogenous, context-sensitive, medically uniquely singular and holistic approach sounds wonderful but for áll illnesses, now it just comes off as a cop-out. “Our tests are insufficient, we have to do better” would be a much better name than MU(P)S.


  2. which was hardly an answer to the question…me and my brainfog shouldn’t be allowed online today ;( so to add; none of them have ever asked me what I think is wrong with M.E

  3. Rani, there is no cause. As I posted back in August (still awaiting comment!), disease is a susceptibility. The “cause” is a disposition. Did I get the flu because I was exposed to it? No, I got it because I had a “hook” for it! Why can 10 people walk down a street but only 1 or 2 get flu? The virus didn’t cause it but one’s reaction to it which is vitalist.

    Which came first, the flu or my susceptibility? Who can say? it’s a chicken and egg situation.

    It’s also important to clarify what one means by “disease.” “Flu”, “IBS” etc. are only names used for convenience by a particular school of medicine which makes it easier for them to prescribe. In reality, no-one’s flu or IBS etc. are the same, there are always variations as disease is an individual thing which makes it hard to understand scientifically but philosophers have to consider this.

    The only way to solve the complexities and variations is forget names and consider each individual’s totality of symptoms as one whole phenomenon as Samuel Hahnemann showed in his Organon of Medicine.

  4. Hi Rani. Yes a fascinating topic and a true observation that I have seen in clinical practice over the last 20 years!!! I wonder how Clean language interviewing might be a useful technique to be applied in this context of research? As an experienced clinician I have noticed a more satisfactory response among my clients when we can focus on their needs and wishes foremost , reduce the sense of uncertainty to a manageable level, optimize clarity, facilitate the direction they want to go in and to allow them to take the steering wheel so they can stay in control of their own vehicle!

  5. Hi Rani! it is great that you take part in an effort to clarify medical conditions witt multiple causes. However the main reason for conditions remaining unexplained, I certainly believe, is lack of thorough and meticulous research. At least in the case of long lasting fatigue progress is finally being made. the progress may not be impressive in terms of causes, but at least in treatment. 25 years of research in biophsychosocial models have brought these pasients nothing but misery and stigma. The research is interpreted by the public in general and Healthcare providers alike as “It’s all in your brain, think yourself well”. Actually, in the case of different fatigue conditions, it requires very creative statistical analysis and very lax admission criteria for patients into studies to find any effect of psychosocial methods. Another really serious problem with psychosocial models is that they leave the field wide open for all sorts of quacks seeing quick profits in courses for “Think yourself well in three days”. What works with our current understanding of these conditions, is for the patients to adjust their activity level and adapt their lifestyle to their capacity.

    Multiple causes, of course, multiple biological causes. Unique treatments for each patient, of course, but based on solid science and an experienced clinical eye. Medically unexplained causes, yes they exist for now, but I doubt there are medically unexplainable symptoms.

  6. I am a specialist physiotherapist in pain management in the UK and have a high caseload of patients with a diagnosis of FMS
    I am very interested in this research as I feel it addresses some very pertinent issues
    Very keen to learn more

  7. Pingback: Fibromyalgi-teori: Ny eller gammel vin? | videnomsmerter

  8. Pingback: The CauseHealth Project | CauseHealth

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