European Headache Federation recommendations for placebo and nocebo terminology

Background and aim

Despite recent publications, practitioners remain unfamiliar with the current terminology related to the placebo and nocebo phenomena observed in clinical trials and practice, nor with the factors that modulate them. To cover the gap, the European Headache Federation appointed a panel of experts to clarify the terms associated with the use of placebo in clinical trials.

Methods

The working group identified relevant questions and agreed upon recommendations. Because no data were required to answer the questions, the GRADE approach was not applicable, and thus only expert opinion was provided according to an amended Delphi method. The initial 12 topics for discussion were revised in the opinion of the majority of the panelists, and after a total of 6 rounds of negotiations, the final agreement is presented.

Results/recommendations

Two primary and mechanism-based recommendations are provided for the results of clinical trials: [1] to distinguish the placebo or nocebo response from the placebo or nocebo effect; and [2] for any favorable outcome observed after placebo administration, the term “placebo response” should be used, and for any unfavorable outcome recorded after placebo administration, the term “nocebo response” should be used (12 out of 17 panelists agreed, 70.6% agreement). The placebo or nocebo responses are attributed to a set of factors including those that are related to the medical condition (e.g. natural history, random comorbidities, etc.), along with idiosyncratic ones, in which the placebo or nocebo effects are attributed to idiosyncratic, or nonspecific mechanisms, exclusively (e.g. expectation, conditioning, observational learning etc.). To help investigators and practitioners, the panel summarized a list of environmental factors and idiosyncratic dynamics modulating placebo and nocebo effects. Some of them are modifiable, and investigators or physicians need to know about them in order to modify these factors appropriately to improve treatment. One secondary recommendation addresses the use of the terms “placebo” and “nocebo” (“placebos” and “nocebos” in plural), which refer to the triggers of the placebo/nocebo effects or responses, respectively, and which are inert agents or interventions that should not be confused with the placebo/nocebo responses or effects themselves (all panelists agreed, 100% agreement).

Conclusion

The working group recommends distinguishing the term response from effect to describe health changes from before to after placebo application and to distinguish the terms placebo(s) or nocebo(s) from the health consequences that they cause (placebo/nocebo responses or effects).

The Meaning Response, "Placebo," and Methods

In 2002, Dan Moerman outlined three candidate explanations for the "placebo response": the "conditioned stimulus-response," Irving Kirsch's "response-expectancy" explanation, and the "meaning response." The meaning response, Moerman argued, was the only one of the three candidate explanations that could cover all the data, gained from decades of RCTs and centuries of historical record. Moerman went so far as to propose replacing the term "placebo effect/response" with the term "meaning response," because people are not responding to placebos, since there is nothing to respond to; people are responding to meanings. There is evidence of medically significant meaning responses where there is no evidence for conditioning. Similarly, there is evidence for such responses where those subject to them lack the knowledge-epistemic capital-required to form the beliefs which might constitute an expectation. Something else, neither conditioning nor propositional attitudes, explained placebo responses, and Moerman proposed the meaning response. While the authors consider the meaning response to avoid the pitfalls of conditioning and response-expectancy, it has been subject to criticism. The criticisms have focused on what is seen as the explanation falling foul of the naturalistic demand and not fitting with prevalent predilections in the philosophy of mind and cognitive science. This article seeks to allay these worries and proposes the inclusion of ethnomethodological fieldwork in future research.

Ethnopharmacological field studies: a critical assessment of their conceptual basis and methods

Ethnopharmacology as a well-defined field has a relatively short history, but for centuries researchers have been interested in the observation, description, and experimental investigation of indigenous drugs and their biological activities. Today, such articles are published in a variety of journals among which the Journal of Ethnopharmacology has a prominent position as well as in book monographs. As any other area of scientific endeavour, this field requires a critical and engaged discussion about the conceptual basis, the relevant methods and the overall standards necessary for excellence. Here we review recent ethnopharmacological field studies in order to highlight achievements and future needs for improving the quality of such studies. The basis for this review is 40 field studies published in the years 2007 and 2008 in the Journal of Ethnopharmacology. Researchers need to have a clear vision for what and how they want to achieve a conceptually and methodologically sound approach and as in all disciplines adherence to internationally recognized methodological standards is essential. Here we review not only the basic conceptual requirements but also the minimal methodological (i.e. botanical, anthropological/historical,ethnomedical) standards and ways how to quantify ethnopharmacological information. Future uses of such information both in the context of experimental research and in applied projects highlight the multiple roles of such data generated in ethnopharmacological field studies. This review cannot be a book of recipes on how to conduct such research but highlights minimal conceptual and methodological requirements for use in future projects.

Agreement and meaning: rethinking consensus analysis

This study provides a critical perspective on "informant agreement (consensus) analysis" as it is used in ethnobotany and ethnopharmacology. It recasts the concept at a higher cultural level, and it describes the cultural agreement about reported medicinal plant use for the native peoples of North America. It examines some plant use categories around which there is significant cross cultural agreement, and some categories which lack such agreement. The study then proposes a theoretical approach to understanding the efficacy of plants lacking significant consensus in their usage. The study considers the implications of this second form of efficacy defined here as the "meaning response", but often referred to as the "placebo effect".

"Symbols and selectivity" revisited

The author recalls how he came to do one of the first statistical analyses of native American medicinal plants, published in volume 1 of Journal of Ethnopharmacology. The background of that paper, "Symbols and Selectivity," involved a great deal of serendipity.

Native Americans' choice of species for medicinal use is dependent on plant family: confirmation with meta-significance analysis

We test the hypothesis that the choice by traditional people of species of plants for medicinal use does or does not depend on the families to which those species belong. Our geographic context is continental North America north of the Rio Grande River. Our plant context is flowering plants. Our ethnological context is Native American traditions. Our null hypothesis is that the probability of any species being medicinal is the fraction of all species that are medicinal, no matter the family to which that species may belong. Classical statistical techniques and the experience of ethnobiologists had already made it clear that among very large plant families, most have either very many or very few medicinal species. Here we use intense computation to simulate thousands of data sets to create predictions to compare with the observed data for medium and small families. Our results clearly show that a surprising number of medium and small families also have very many or very few medicinal species. Recent molecular, fossil and cytological studies have confirmed the evolutionary naturalness of most plant families. This suggests that species in the same family may have inherited from common ancestors similar ecological adaptations, such as ways to protect themselves from herbivores, pathogens or decomposers. Some of these adaptations affect the physiology of the attacking organisms, suggesting an explanation for the clear preferences of Native American traditions to choose medicinal species from some families much more than from others, regardless of the size of those families.

The meaning response and the ethics of avoiding placebos

Because the "placebo effect" seems to result from "deception," it is often disparaged and despised. Rethinking this and realizing that these benefits flow largely from the meaning of medical encounters (and are far better understood as "meaning responses"); realizing that there need be no deception to elicit them and that they are often very desirable, engaging fundamental human biological pathways, puts the ethical dilemma in a new light. It seems unethical to avoid--to evade--coming to a full understanding of how meaning can so profoundly improve human well-being.

Deconstructing the placebo effect and finding the meaning response

We provide a new perspective with which to understand what for a half century has been known as the "placebo effect." We argue that, as currently used, the concept includes much that has nothing to do with placebos, confusing the most interesting and important aspects of the phenomenon. We propose a new way to understand those aspects of medical care, plus a broad range of additional human experiences, by focusing on the idea of "meaning," to which people, when they are sick, often respond. We review several of the many areas in medicine in which meaning affects illness or healing and introduce the idea of the "meaning response." We suggest that use of this formulation, rather than the fixation on inert placebos, will probably lead to far greater insight into how treatment works and perhaps to real improvements in human well-being.

Reviewing the reviews. How strong is the evidence? How clear are the conclusions?

OBJECTIVES

The objectives of this paper were: a) to determine what can be learned from conclusions of systematic reviews about the evidence base of medicine; and b) to determine whether two readers draw similar conclusions from the same review, and whether these match the authors' conclusions.

METHODS

Three methodologists (two per review) rated 160 Cochrane systematic reviews (issue 1, 1998) using pre-established conclusion categories. Disagreements were resolved by discussion to arrive at a consensual score for each review. Reviews' authors were asked to use the same categories to designate the intended conclusion. Interrater agreements were calculated.

RESULTS

Interrater agreement between two readers was 0.68 and 0.72, and between readers and authors, 0.32. The largest categories assigned by methodologists were "positive effect" (22.5%), "insufficient evidence" (21.3%), and "evidence of no effect" (20.0%). The largest categories assigned by authors were "insufficient evidence" (32.4%), "possibly positive" (28.6%), and "positive effect" (26.7%).

CONCLUSIONS

The number of reviews indicating that the modern biomedical interventions show either no effect or insufficient evidence is surprisingly high. Interrater disagreements suggest a surprising degree of subjective interpretation involved in systematic reviews. Where patterns of disagreement emerged between authors and readers, authors tended to be more optimistic in their conclusions than the readers. Policy implications are discussed.

The importance of weeds in ethnopharmacology

Tropical primary forest is often considered to be the most important habitat for traditional peoples to gather medicinal plants. However, the role of weeds, commonly found in disturbed areas, in traditional medicinal floras has been overlooked. Data are presented showing the significant representation of weeds in the medicinal floras of the Highland Maya in Chiapas, Mexico and in the medicinal flora of Native North Americans as a whole. The frequency with which weeds appear in these pharmacopoeias is significantly larger (P<0.0001) than what would be predicted by the frequency of weed species in general. Explanations based on human ecology and biochemical ecology are presented.

Toward a research agenda on placebo

The placebo effect is about healing. The human healing process can be substantially influenced in actual medical practice by appropriate kinds of caring, communication, and patient empowerment. The creation of "meaning" and of "representations" by physicians and their patients can have dramatic effects on patients for good or ill. These effects are potentially as important in procedures such as surgery or chiropractic as they are in medicine generally. Placebo processes can substantially affect the overall response to health care and its cost, yet very little research specifically explores these phenomena. An explicit research agenda should be developed to investigate the influences of belief, context, and meaning in medicine. Such a research agenda would have significant beneficial scientific and policy consequences. In addition, it would enhance our understanding of those healing processes that underlie most if not all of medicine.

Cultural variations in the placebo effect: ulcers, anxiety, and blood pressure

An analysis of the control groups in double-blind trials of medicines demonstrates broad variation--from 0 to 100 percent--in placebo effectiveness rates for the same treatment for the same condition. In two cases considered here, drug healing rates covary with placebo healing rates; placebo healing is the ultimate and inescapable "complementary medicine." Several factors can account for the dramatic variation in placebo healing rates, including cultural ones. But because variation differs by illness, large placebo effects for one condition do not necessarily anticipate large placebo effects for other conditions as well. Deeper understanding of the intimate relationship between cultural and biological processes will require close ethnographic scrutiny of the meaningfulness of medical treatment in different societies.

Placebo effect in the treatment of duodenal ulcer

AIMS

To assess whether frequency of placebo administration is associated with duodenal ulcer healing.

METHODS

A systematic literature review of randomized clinical trials was undertaken. 79 of 80 trials that met the inclusion criteria. The pooled 4 week placebo healing rate of all duodenal ulcer trials that employed a four times a day regimen was compared with the rate obtained from trials with a twice a day regimen.

RESULTS

The pooled 4 week healing rate of the 51 trials with a four times a day regimen was 44. 2% (805 of 1821 patients) compared with 36.2% (545 of 1504 patients) in the 28 trials with a twice a day regimen (difference, 8.0% [equal effects model]; 95% confidence interval, 4.6% to 11.3%). Depending on the statistical analysis, the rate difference ranged from 6.0% (multivariable random effects model) to 8.0% (equal effects model). A number of sensitivity analyses showed comparable differences between the two regimens. Most of these sensitivity analyses were not significant, probably because a number of trials were excluded resulting in a loss of power.

CONCLUSIONS

We found a relation between frequency of placebo administration and healing of duodenal ulcer. We realize that the comparison was based on nonrandomized data. However, we speculate that the difference between regimens was induced by the difference in frequency of placebo administration. A better knowledge of various placebo effects is required in order to make clinically relevant assessments of treatment effects derived from placebo-controlled trials.

An analysis of the food plants and drug plants of native North America

This paper compares the medicinal and food floras of the native peoples of North America. There is a surprising overlap of these floras by both family and taxon. Yet there are also substantial differences-food and medicine tend to involve different plant parts, plant habit, and plant character. The similarities and differences are considered in an evolutionary context and a theoretical perspective is suggested to account for these facts.

The medicinal flora of Native North America: an analysis

This paper describes an analysis of the plants of North America which have been used medicinally by Native North Americans. A method using regression residuals is developed for analyzing large quantities of data, divided into subgroups of varying sorts and sizes. The analysis shows that the medicinal species utilized by Native North Americans are distributed in a highly non-random fashion across subclasses and families as well as across groups defined in terms of growth habit and life pattern. This distribution makes sense in terms of both the defensive chemistry and the "complexity" of plants.

"Functioning" from the perspective of production supervisors

Ethnographic research at two work activity centers revealed the hidden connotations of "functioning" in production supervisors' discussions of high functioning and lower functioning clients. Teachers at the centers defined functioning in narrowly academic terms, whereas supervisors used the term to connote a whole set of mental, physical, and moral traits related to job performance. Implications for communication among staff members and for treatment of clients were considered.

Symbols and selectivity: a statistical analysis of native American medical ethnobotany

Native Americans use a wide range of plants medicinally. Many of these plants have profound meaning to their users. Does this mean, as some assert, that tribal medicine is "all placebo"? Since the essential character of meaning is the arbitrariness of the sign, then insofar as this medicine is symbolic, the plants used medicinally will be a random representation of plants available in nature. Several regression analyses of plants used by native Americans on plants available to them indicate substantial selectivity in plant use. Native American medical ethnobotany is not only placebo medicine.