Background: Placebo and nocebo effects occur in clinical or laboratory medical contexts after administration of an inert treatment or as part of active treatments and are due to psychobiological mechanisms such as expectancies of the patient. Placebo and nocebo studies have evolved from predominantly methodological research into a far-reaching interdisciplinary field that is unravelling the neurobiological, behavioural and clinical underpinnings of these phenomena in a broad variety of medical conditions. As a consequence, there is an increasing demand from health professionals to develop expert recommendations about evidence-based and ethical use of placebo and nocebo effects for clinical practice. Methods: A survey and interdisciplinary expert meeting by invitation was organized as part of the 1st Society for Interdisciplinary Placebo Studies (SIPS) conference in 2017. Twenty-nine internationally recognized placebo researchers participated. Results: There was consensus that maximizing placebo effects and minimizing nocebo effects should lead to better treatment outcomes with fewer side effects. Experts particularly agreed on the importance of informing patients about placebo and nocebo effects and training health professionals in patient-clinician communication to maximize placebo and minimize nocebo effects. Conclusions: The current paper forms a first step towards developing evidence-based and ethical recommendations about the implications of placebo and nocebo research for medical practice, based on the current state of evidence and the consensus of experts. Future research might focus on how to implement these recommendations, including how to optimize conditions for educating patients about placebo and nocebo effects and providing training for the implementation in clinical practice.

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Based upon prior research identifying dispositional optimism as a predictor of placebo responding, the present study tested the hypothesis that individuals high in optimism would be more likely to respond to a placebo analgesic. Optimists and pessimists were randomly assigned to a placebo expectation condition or a no expectation condition prior to a cold pressor task. Blood pressure and heart rate were recorded before and during the cold pressor task, and participant ratings of pain and expectations were obtained immediately after the task. Analysis of the expectation manipulation revealed that the placebo instruction was successful in altering participant expectancy during the cold pressor. Supporting the main hypothesis, dispositional optimism was associated with lower pain ratings in the placebo condition but not in the control condition. Because dispositional optimism can alter placebo responding to laboratory pain, future studies should examine the potential role that this individual difference factor may play in patient responsivity to pharmacological and non-pharmacological treatments for clinical pain.

Motivational factors receive little attention in current theories of the placebo effect. Reasons for this position are reviewed, and an argument is made for reconsidering the influence of motivation on the placebo effect. The authors hypothesize that nonconscious goals alter reactions to a placebo expectation. Specifically, the authors predict that the placebo effect is most likely to occur when individuals have a goal that can be fulfilled by confirmation of the placebo expectation. The authors tested this notion in 5 experiments. The results demonstrate the role of motivation in the placebo effect across a variety of symptom domains and via 4 different goal activation techniques. Moreover, this moderating effect occurred for both positive and negative placebo expectations, across different placebo effect measures, and in brief laboratory experiments as well as in lengthier studies. It is argued that theories regarding the placebo effect should incorporate motivational factors. Keywords: expectations, goals, health, placebo effectThe word placebo entered the English language around the 13th century (Shapiro, 1964). The word was translated from Vulgate Latin, meaning to please, to give pleasure, to suit, and to satisfy (Lasagna, 1986;Lewis, 1953;Shapiro & Shapiro, 1997). Early medical definitions include "a medication given to please" (Dorland, 1901) and "medicines prescribed more to please the patient than for its therapeutic effectiveness" (Fox, 1803).These initial conceptualizations of a placebo clearly possess a strong motivational element. That is, a placebo was originally viewed as a medication or treatment that was administered to fulfill a need or desire of the patient. In contrast, most recent reviews and research articles on the placebo effect either ignore or discount the potential impact that motives can have on placebo responding (e.g., Ader, 1997;Amanzio & Benedetti, 1999;Bienenfeld, Frishman, & Glasser, 1996;Kienle & Kiene, 1996;Kirsch, 1997;Montgomery & Kirsch, 1996;Ross & Olson, 1982;Stewart-Williams & Podd, 2004). The aim of this article is to reintroduce motivational features to the theory of the placebo effect. We begin by presenting a brief review of the relevant literature and discussing the dominant theoretical perspectives of the placebo effect. Next, we present a model of placebo responding based on recent goal activation research. We then report five studies conducted to assess this motivationally oriented account. The Placebo EffectWhat is the placebo effect? Although a wide array of definitions currently exist (see

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