In 1995, the World Health Organization (WHO) "Guidelines for Clinical Research on Acupuncture" stipulated three criteria for good acupuncture studies: validity, reliability, and statistical significance.

Since then, double-blind randomized controlled trials (RCTs) have become the gold standard for testing the efficacy of acupuncture in clinical research.

Almost two decades later, well-designed RCTs with an appropriate control group are still needed to evaluate the efficacy of acupuncture – as the ongoing debate about the therapeutic effects of acupuncture for some diseases shows.

The need for an appropriate control group is caused by the fact that so far most trials have used placebo as a control group, leading to the so-called "placebo effect". This phenomenon can affect the study efficacy results, causing the lack of statistical significance between the test treatment and the placebo. Placebo-controlled trials can show high rates of placebo response, especially in conditions with subjective outcomes. Nevertheless the positive response to placebo does not mean that placebo caused the response. This is because the apparent placebo response may result from many factors, such as the use of an improper placebo, symptom fluctuation/spontaneous remission or patients' expectation that can play a powerful role per se in the "placebo effect".

The real challenge to minimize the "placebo effect" in acupuncture RCTs is determining the proper placebo. This should be both physiologically inert and indistinguishable from the active treatment in order to achieve a high level of scientific validity.

So far experimental clinical data on acupuncture have shown contradictory results when using a control group. In some studies verum and placebo acupuncture treatments were both better than no-treatment while in other studies verum acupuncture was significantly more effective than placebo acupuncture or there was no clear demonstration of the superiority of verum acupuncture efficacy over placebo treatment.

Based on these considerations, before designing any further RCT, clinical acupuncturist researchers should ask themselves if it is really possible to minimize the "placebo effect" in acupuncture clinical studies and - if so - what kind of placebo can be considered the most indistinguishable and inert.