Sir,

Within medicine, there is a strong focus on the so-called "hierarchy of evidence", which places different weights on various forms of scientific evidence. At the bottom of this pyramid stands the solitary case report an individual report on the progress of one patient. At the top of the pyramid, the randomised controlled trial (RCT) stands proud.

While we are big believers in Ayurveda, our medical colleagues often trivialise its efficacy citing the lack of randomised controlled trials supporting its use. It must be said that this comment is not without merit:

It eliminates bias in treatment assignment.It facilitates blinding of the identity of treatments from investigators, participants and assessors.It permits the use of probability theory to express the likelihood that any difference in outcome between treatment groups merely indicates chance.

However, we suggest that this appraisal is not entirely fair. The nature of Ayurveda precludes the straightforward administration of randomised controlled trials to measure it. Two individuals who may have the same medical diagnosis may have different symptoms and personalities, and therefore will be prescribed different remedies. Thus, two important aspects of Ayurveda, individual prescribing and attention to non-medically recognised symptoms, render the use of RCT methodology problematic.

There is also the issue of bias in funding of clinical trials and the vested interests of the powerful pharmaceutical industry influencing the so-called neutrality and objectivity of much RCT data. As Hess argues, "It takes a lot of gold to meet the gold standard of the clinical trial",\[[@ref1]\] within Ayurveda there are rarely powerful pharmaceutical interests and therefore few trials.

In addition to the question of availability of evidence, concepts embedded within the notion of RCT evidence are problematic. A placebo in medical terms is supposed to be an inert substance yet it is known to exert around a 35% improvement effect.\[[@ref2]\] Di Blasi and Kleijnen demonstrate that the existence of a placebo option is capable of changing patient responses even in non-placebo arms of an RCT. Merely knowing that they might potentially be on placebo reduced the response of participants given an active drug.\[[@ref3]\]

Wolpe raises the paradox that many of the most powerful phenomena in orthodox medicine, the placebo effect, psychosomatic illness and spontaneous remission, which can account for large percentages of healing rates, get very little research attention.\[[@ref4]\] Mythological, ritualised and culturally embedded aspects of all healing systems, medicine included, can in themselves possess great healing potential. Orthodox medicine can be blind to such aspects of its own practice in its claim to scientific legitimacy, and these elements are not studied in the RCT. Yet it is often these very aspects that attract patients to Ayurveda.

Thus, we state that while the randomised controlled trial may be the perfect fit for high-quality medical evidence, this is not necessarily the case in Ayurveda. Lack of such evidence should therefore not be interpreted as lack of efficacy.
