Rigorous research into the effectiveness of a therapy should tell us the truth about the ability of this therapy to treat patients suffering from a given condition — perhaps not one single study, but the totality of the evidence (as evaluated in systematic reviews) should achieve this aim. Yet, in the realm of alternative medicine (and probably not just in this field), such reviews are often highly contradictory.
A concrete example might explain what I mean.
There are numerous systematic reviews assessing the effectiveness of acupuncture for fibromyalgia syndrome (FMS). It is safe to assume that the authors of these reviews have all conducted comprehensive searches of the literature in order to locate all the published studies on this subject. Subsequently, they have evaluated the scientific rigor of these trials and summarised their findings. Finally they have condensed all of this into an article which arrives at a certain conclusion about the value of the therapy in question. Understanding this process (outlined here only very briefly), one would expect that all the numerous reviews draw conclusions which are, if not identical, at least very similar.
However, the disturbing fact is that they are not remotely similar. Here are two which, in fact, are so different that one could assume they have evaluated a set of totally different primary studies (which, of course, they have not).
One recent (2014) review concluded that acupuncture for FMS has a positive effect, and acupuncture combined with western medicine can strengthen the curative effect.
Another recent review concluded that a small analgesic effect of acupuncture was present, which, however, was not clearly distinguishable from bias. Thus, acupuncture cannot be recommended for the management of FMS.
How can this be?
By contrast to most systematic reviews of conventional medicine, systematic reviews of alternative therapies are almost invariably based on a small number of primary studies (in the above case, the total number was only 7 !). The quality of these trials is often low (all reviews therefore end with the somewhat meaningless conclusion that more and better studies are needed).
So, the situation with primary studies of alternative therapies for inclusion into systematic reviews usually is as follows:
- the number of trials is low
- the quality of trials is even lower
- the results are not uniform
- the majority of the poor quality trials show a positive result (bias tends to generate false positive findings)
- the few rigorous trials yield a negative result
Unfortunately this means that the authors of systematic reviews summarising such confusing evidence often seem to feel at liberty to project their own pre-conceived ideas into their overall conclusion about the effectiveness of the treatment. Often the researchers are in favour of the therapy in question – in fact, this usually is precisely the attitude that motivated them to conduct a review in the first place. In other words, the frequently murky state of the evidence (as outlined above) can serve as a welcome invitation for personal bias to do its effect in skewing the overall conclusion. The final result is that the readers of such systematic reviews are being misled.
Authors who are biased in favour of the treatment will tend to stress that the majority of the trials are positive. Therefore the overall verdict has to be positive as well, in their view. The fact that most trials are flawed does not usually bother them all that much (I suspect that many fail to comprehend the effects of bias on the study results); they merely add to their conclusions that “more and better trials are needed” and believe that this meek little remark is sufficient evidence for their ability to critically analyse the data.
Authors who are not biased and have the necessary skills for critical assessment, on the other hand, will insist that most trials are flawed and therefore their results must be categorised as unreliable. They will also emphasise the fact that there are a few reliable studies and clearly point out that these are negative. Thus their overall conclusion must be negative as well.
In the end, enthusiasts will conclude that the treatment in question is at least promising, if not recommendable, while real scientists will rightly state that the available data are too flimsy to demonstrate the effectiveness of the therapy; as it is wrong to recommend unproven treatments, they will not recommend the treatment for routine use.
The difference between the two might just seem marginal – but, in fact, it is huge: IT IS THE DIFFERENCE BETWEEN MISLEADING PEOPLE AND GIVING RESPONSIBLE ADVICE; THE DIFFERENCE BETWEEN VIOLATING AND ADHERING TO ETHICAL STANDARDS.