Effects of placebo interventions on gastric motility and general autonomic activity Karin Meissner ⁎ Institute of Medical Psychology, Ludwig-Maximilians University, Munich, Germany Received 28 April 2008; received in revised form 21 July 2008; accepted 2 September 2008 Abstract Objective: The study aimed to investigate placebo effects on gastric motility and to examine possible autonomic mediating mechanisms. Methods: Eighteen healthy volunteers received a placebo pill on three occasions together with the verbal suggestion that it would stimulate, relax, or not affect gastric activity. Electrogastrogram, electrocardiogram, and electrodermal activity recordings were conducted for 30 min prior to and following intervention. Results: Dominant frequency of the gastric slow wave decreased in the stimulant condition, and increased in the relaxant condition, the difference among conditions being significant. No differential effects of the interventions on cardiac interbeat intervals, heart rate variability, and skin conductance levels were observed. Conclusion: Stomach relaxant and stimulant placebo interventions modulated gastric motility in- dependently from changes in general autonomic activity. © 2009 Elsevier Inc. All rights reserved. Keywords: Autonomic nervous system; Electrogastrography; Gastric Motility; Physiology; Placebo effect; Suggestion Introduction In randomized controlled trials of gastrointestinal dis- orders, high placebo response rates of about 40%, on average, have been observed [1–3]. The amount to which the improvement in the placebo groups is due to the placebo interventions itself, or is related to other factors, like regression to the mean or the natural history of the disease, remains unclear because natural history groups necessary to control for placebo-unrelated factors [4] usually are missing. One recent controlled trial investigating placebo effects in irritable bowel syndrome included a natural history control group and found clear evidence for placebo effects on subjective outcome parameters, such as the global improve- ment scale and adequate relief of symptoms [5]. Whenever objective outcome parameters for a disease are lacking, however, the possibility that improvement of placebo-treated patients is not due to a change in disease severity but to erroneously detected symptomatic relief [6] cannot be fully excluded [5]. Closely related to the question whether placebo effects in gastrointestinal diseases really exist is therefore the basic question whether mere suggestive interventions have the power to affect gastrointestinal functions. Up to now, there are only a few experimental studies shedding light on this issue. Levine et al. [7] investigated the effects of placebo and nocebo administration on motion sickness and found the gastric correlate of nausea, i.e., gastric tachyarrhythmia, to be reduced in the nocebo-treated group. As early as 1964, Sternbach [8] had addressed the more direct effects of placebos and verbal suggestions on gastric motility: six healthy volunteers received a placebo drug on three occasions described as being stimulating, relaxing or not affecting gastric motility. Gastric contraction periods were shorter following the gastric stimulant intervention and longer following the gastric relaxant intervention, as Journal of Psychosomatic Research 66 (2009) 391 – 398 ⁎ Institute of Medical Psychology, Ludwig-Maximilians-Universität München, Goethestrasse 31, 80336 Munich, Germany. Tel.: +49 89 2180 75613; fax: +49 89 2180 75615. E-mail address: karin.meissner@med.uni-muenchen.de. 0022-3999/08/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jpsychores.2008.09.004