What is evidence?

In medicine there is always the justified question of whether something is working or not and what is the best course of action for a particular illness or complaint. Consider, for example, the discussions about vaccinations, the reports about medicines for depression, the debate about the efficacy of alternative medicine. In this piece I will discuss a few types of evidence with a number of criticisms.


Natural scientific evidence

With proof can be meant: the scientific evidence. This is a materialistic thinking model and seems to be all-encompassing. Yet there are limitations. One of them is that not everything can be explained or proven from this model. An example: despite much brain research, we still do not know what consciousness is, how it originates, and where it is. It may of course be that more research needs to be done to discover this. In practice, however, it appears that getting an answer to a question leads to more questions. Another limitation is that the observer influences the phenomenon to be observed. Example: depending on how light is looked at, it behaves like particles or waves. The reality around us changes by looking at it differently! A third limitation is that often facts or events are ignored that do not fit the thinking model. For example, spontaneous healing of cancer. As a result, it is difficult to come up with new or different ideas in the current thinking model.


Epidemiological evidence

A lot of epidemiological evidence is also used in medicine. By examining large groups of people and summarizing the outcomes, a certain image is created that is adopted for 'true'. The the various guidelines and standards make use of this knowledge to state how to deal with certain diseases and complaints. In particular the comparative research (the so-called randomized controlled trials - RCT), in which groups of people with the same problem are offered a different therapy, is highly valued. Yet there is fundamental criticism here. An example: in this type of research we look at the effectiveness of different therapies. However, if the indication for that therapy is not correct (the diagnosis), then the outcome measures the quality of the diagnosis and not the effectiveness of the therapy. Another example: the research is always done in closely defined groups of people. This means that the outcome is in principle only valid for this group. Thus, little data is available for therapies in old people, non-white people, and so on. Another example: when different researchers get the same research data, they regularly draw different conclusions. This means that the facts are susceptible to different interpretations.


Alternative medicine

Alternative medicine is called alternative because the thought model/theory is very different or conflicts with scientific thinking, and according to (natural) scientific and epidemiological researchers there is no or insufficient proof of efficacy. This is contradicted by researchers from the alternative sector. Who is right? I do not know, see the marginal notes on scientific and epidemiological evidence.


Evidence and patient care

Perhaps in everyday practice, regular or alternative, it is good to realize that science is something different than treating patients. Science is interested in what works, and the patient wants to know what will help him/her. Science can help to decide what is the best policy at the time, but that does not mean that it will work for this patient. And that can mean that deviating from the scientifically established guidelines can turn out to be beneficial for a number of patients. It is the task of the physician to draw up specific treatment for everyone with the knowledge of science and the individual characteristics of the patient.


Scott R, et al. A philosophical analysis of the evidence-based medicine debate. BMC Health Services Research 2003, 3:14.
Smulders YM, Levi M, Stehouwer CDA, Kramer MHH, Thijs A. De rol van epidemiologisch bewijs in de zorg voor individuele patiƫnten. Ned Tijschr Geneeskunde 2010;154,19:892-5.