4.2 The conclusions from research into the efficacy of the various CAMs are outside the remit of this report. However, it is necessary to understand the general state of the CAM evidence base, in order to consider what type of evidence needs to be collected and to understand why CAM's claims often cause controversy.

4.3 CAM has been criticised by some witnesses for not having scientific evidence to back its claims. The Academy of Medical Sciences (P 1) told us that they are concerned that many CAM practitioners do not take a 'scientific' approach to treatment. They suggest that whereas conventional medicine makes efforts to conduct rigorous research, and changes its clinical practice when new information is discovered, CAM practitioners are more likely to stick to their belief systems despite any negative evidence that may emerge. This is one reason the Academy of Medical Sciences uses to explain why CAM lacks an adequate evidence base to convince them, as conventional scientists, of its claims. This is a controversial statement, and as discussed in para 2.19, Sir Iain Chalmers, Director of the UK Cochrane Centre, suggested that conventional medicine is biased against CAM and conventional medical practitioners and scientists are likely to require lower standards of proof for conventional medical treatments then they do for CAM (P 225). Nevertheless, as we concluded in para 2.7, we are satisfied that there is at present no credible evidence base to support the value of any of the therapies that we list in our Group 3.

4.4 The Department of Health summed up their opinion of the evidence base for CAM by saying that "Evidence for CAM in the form of research has been criticised as being inadequate, and there is some justification in this claim" (P 101). This is a controversial area, as the definition of an adequate evidence base varied across our witnesses. Some CAM practitioners have claimed that a history of safe and apparently successful traditional use is enough evidence to justify advocating the use of their particular therapy. However, most of our witnesses with a conventional medical or scientific background have asserted that, in order for CAM therapies to be more widely accepted, it is important that they have a critical mass of scientifically-controlled evidence to support their claims; and that at the moment most of CAM lacks such evidence. Many of our conventional medical witnesses have suggested that, since much of conventional medicine is required to undergo rigorous trials to justify its use, no less should be expected of CAM. But even this view is controversial as some of the CAM advocates we have heard from have suggested that much of conventional medicine lacks a rigorously tested evidence base, and that to require one of CAM is to operate a double standard. In fact, the Department of Health followed their statement that there was some justification behind the claim that the CAM evidence base was inadequate, by acknowledging that the same could be said for some conventional medicine. It is our view that most modern conventional therapies are backed by scientific evidence. It is in the case of some of the older and traditional treatments surviving from the past (such as cold 'cures' and 'tonics') where evidence is, like the evidence for much of CAM, lacking.

4.19 Evidence that a therapy has few, if any, significant adverse effects and will not cause avoidable harm must be considered important in all medicine, including CAM. However, there are two potential complications which confound this seemingly simple statement:

• What level of safety should be demanded?

• What type of evidence of safety is acceptable?

4.20 In determining what level of safety should be sought, the risk/benefit ratio of the therapy in question must be considered. If the potential benefits of a therapy are likely to be very significant, or even life-saving, then the level of risk a patient may be willing to take with the therapy is likely to be higher than the level of risk they are willing to accept for the benefit of temporary symptom relief or the cure of a minor complaint. Another consideration is whether the risks a therapy may possess are inherent or can be minimised through proper regulation of its practitioners. For example we received some evidence about the risks of acupuncture causing pneumothorax due to a needle being inserted into the pleural cavity; however if practitioners are properly trained and well-regulated this risk is minimised. In determining what evidence of safety is acceptable it is important to consider what weight should be given to a history of safe traditional use. Within CAM such evidence is common and is often given reasonable weight by CAM advocates and to a certain extent by policy-makers. For example there are exemptions from licensing in the Medicines Acts for natural remedies of traditional use, and a third category of medicines, which will include traditional-use herbal medicines, is being examined by the European Union (see Chapter 5).

4.21 There is no doubt that many CAM therapies are very safe, as compared to many new powerful conventional remedies. This is often used as an argument for approving the increasing use of CAM, but it must be remembered that the use of a "safe" CAM remedy to treat a serious or potentially lethal disease, so that the use of conventional preparations with proven efficacy is denied, is of course a real danger.

4.22 Several submissions we received suggest that minimum standards of safety need to be defined and widely disseminated in order to protect the public. The British Holistic Medical Association have suggested that such work should be carried out by NICE and the Commission for Health Improvement (CHI) who should then issue national guidelines.

4.23 The evidence that we received from almost all the different therapies indicated that at the point of diagnosis, if the practitioners thought that their treatment would not work, they would refer their patients to a conventional medical practitioner. We were encouraged by this sentiment, even though it was not universal.

4.28 The position of therapies without a scientifically plausible mechanism of action (e.g. healing and homeopathy) needs to be considered. If there is no scientifically plausible mechanism through which a treatment may work in the human body, can the use of such a therapy be justified? Should such therapies be considered a product of the placebo effect enhanced by "tender loving care" or should consideration be given to the possibility that they may have explanations not yet understood by modern science? (The role of the placebo effect is discussed in paras 3.19-3.34.)

4.29 Many of our witnesses have argued that if there is evidence for efficacy then it is not necessary to understand exactly how the effect is achieved, and we agree. This is, indeed, the position with several conventional therapies. Professor Sir Michael Rawlins explained that in NICE's search for clinical excellence, it is evidence of efficacy and not the mechanism of action that is prioritised: "I do not mind and I do not think the Institute minds whether it understands how a treatment works or not. I do not understand how many treatments do work, and this is after 35 years as a pharmacologist, but what we do like is good evidence that they do whatever they claim to do" (Q 1833).

4.30 However, despite these arguments, the opposite view is that if a therapy has no plausible mechanism of action then spending research money on it and providing patients with access to it is likely to be a waste of resources. It is worth considering this argument in more detail, by asking two distinct questions:

• Should mechanisms of action be plausible before research into the efficacy of a therapy is funded?
• Should mechanisms of action be understood before access to a therapy is provided?

4.31 It is of course true that many treatments have been used for a long time without understanding their mechanisms of action and only now are possible explanations for how they work coming to light. Professor Lesley Rees, a Trustee of FIM, used acupuncture as a case in point. Acupuncture is traditionally said to work through affecting energy meridians that according to Traditional Chinese medicine circulate around each person. This explanation is not congruent with current scientific thought and if an understanding of mechanisms of action were considered of paramount importance doctors should have shunned acupuncture years ago. Now, however, other possible mechanisms, which are more amenable to modern scientific thought (e.g. concerning the effect on the central nervous system and the stimulation of endorphin receptors), are being discovered and evidence for acupuncture's efficacy is growing. As Professor Lesley Rees summed up: "…acupuncture has been used for thousands of years, yet there was no real information about how it might work and I think it would be fair to say that it would have been terrible if the benefits of acupuncture had not been appreciated and used over all the years because we did not have any real understanding of perhaps some of the mechanisms about how they work" (Q 77).

4.32 In terms of research Professor Tom Meade from the Royal Society told us that "…the distinction between the effect and the explanation for the effect is central, and you do not need to believe in the explanation in order to believe in the effect" (Q 181). Therefore, "...it would be perfectly possible for a funding body to allow a bit of research to go forward even though the theoretical backdrop is totally irrelevant to whether the treatment works or not. I think probably what we will see now, increasingly, is applications for funds which simply say 'There is good reason to think there is an effect here and we want to study that. We are going to use these methods which are well attested.' And if everyone agrees that then, if this works out, it will reduce the ambiguity of the effectiveness of this particular treatment" (Q 181).

4.33 A reason for funding efficacy studies of therapies without a plausible mechanism of action is that research into that area can help elucidate routes through which mechanisms of action might work. Professor Meade explained: "…I think it is possible, in some circumstances, that the result of the trial - in other words that something is effective - will actually then give clues as to studying the mechanisms. Equally, if it is not effective then it is beginning to exclude possible explanations as well" (Q 181).

4.34 However, there is an alternative view, articulated by Professor Lewis Wolpert, a fellow of the Academy of Medical Sciences, that: "It is not just efficacy that you should be thinking about. Medicine aims to base itself upon science. Let me tell you what I mean. If you have therapy which you can in no plausible way relate to the behaviour of cells…I personally could not support research in that field" (Q 1404). Based on the limited amount of research funding available in the medical sciences, he suggests that research into therapies such as homeopathy should not be funded: "A liquid which contains no active molecule, which no chemist could plausibly give an account of, is not an area where I would want to invest money. I am sorry: one cannot give up all of chemistry just because one believes homeopathy works" (Q 1404 and 1406). Professor Patrick Bateson, giving evidence on behalf of the Royal Society, summed up this argument by saying the role of mechanisms of action comes into importance because "... the critical thing here is going to be whether there is enough evidence to justify us spending more time and trouble testing the efficacy and safety of treatment" (Q 175).

4.35 The mechanism through which homeopathy may work on the body is a specific case in point, about which we have heard much. Samuel Hahnemann at the turn of the 19th century put forward the "law of similars", claiming that any disease can be treated successfully with minute amounts of a drug which in larger doses gives rise to the same symptoms. Therefore, homeopathy is based on the idea of treating 'like with like' by administering hugely diluted versions of basically dangerous substances, such that a dose given to a patient may not contain even a single molecule of the active principle. Many conventional doctors and scientists cannot accept that infinitesimal dilutions can have any effect on the body.

4.36 The arguments about homeopathy illustrate the weight given to understanding mechanisms of action. The Department of Health explained their position on homeopathy which clearly shows they prioritise safety before anything else and give less weight to issues of scientific plausibility: "In relation to homeopathic medicines, we very much agree that there is uncertainty, or limited evidence, about the specific mechanism whereby homeopathy works. The starting point is that homeopathic medicines as such are very much at the safe end of the spectrum; they are very dilute. Often these substances do not have a clearly measurable effect on the body, which is why the simplified homeopathic registration scheme introduced in 1994 concentrates specifically on safety and quality and not efficacy. We have taken a fairly pragmatic approach: if homeopathy does not harm then it is less important to have an in-depth understanding of its mechanism for effectiveness" (Q 34).

4.37 In terms of research funding for therapies without a scientifically plausible mechanism of action, it seems that opinion within the world of conventional medicine is very divided. However, we recommend that if a therapy whose mechanism of action is unclear does gain sufficient evidence to support its efficacy, then the NHS and the medical profession should ensure that the public have access to it and its potential benefits.

4.38 The question of NHS provision for therapies such as homeopathy was answered by the Department of Health by prioritising safety together with consumer choice. On the other hand, as evidence from the Academy of Medical Sciences suggests, the only reason for using therapies such as homeopathy is as a vehicle for the placebo effect to work safely (see paras 3.19 - 3.34). Professor Peter Lachmann told us: "Other effects of homeopathy apropos the placebo effect have already been mentioned and I personally am entirely happy with the idea that homeopathy is a good way of administering a placebo because it is free from harm. I am well aware of the fact that in conventional medicine placebo effects are sometimes produced by the administration of drugs. That is less harmless because all drugs have some side-effects. If drugs are given not for a good purpose but just given to make the patients feel that something is being done for them, then I would entirely agree that a homeopathic preparation, which would produce the same placebo effect without possible harmful side-effects, is to be preferred" (Q 1410).

4.39 The intricate arguments concerning the use of the placebo effect as a therapy were discussed in chapter 3; this does not contradict the argument that safety is a priority, and as long as a therapy is safe, use of any benefits it may bring to patients is justifiable without necessarily understanding its mechanisms. In an era when the Government are hoping that NHS treatments will live up to a standard of evidence set by NICE, we welcome the fact that, as the quotation from Professor Sir Michael Rawlins shows, NICE are willing to accept that a therapy can be efficacious and worth considering even when its mechanisms of action are unclear (see para 4.29).