There is an increasing demand from health professionals to develop recommendations about evidence-based and ethical use of placebo effects in the clinical practice, but the underlying mechanisms...Show moreThere is an increasing demand from health professionals to develop recommendations about evidence-based and ethical use of placebo effects in the clinical practice, but the underlying mechanisms behind the placebo effect are not all known yet. One of these mechanisms is observational learning, which is the topic of this study. The current research has two research aims. First, the influence of observational learning on the placebo effect is investigated. Second, the mediating effect of pain expectations in the role of observational learning on the placebo effect is studied. Based on previous findings it was expected that observational learning would induce placebo responses and that pain expectations would mediate this effect. Twenty-three healthy students from 18 to 30 years old participated in this study, which was a single-blinded randomized controlled trial. Placebo analgesia was measured as the difference in pain scores between the activation and the deactivation of a sham device over the course of 18 trials. Pain scores were given on the Numeric Rating Scale (NRS), with scores between 0 and 10. Placebo analgesia was compared in two groups: an observational learning group and a control group. Both groups received painful stimuli in combination with fake activation ore fake deactivation of a sham device. Participants in the observational learning group watched a video in which a model showed analgesic effects after every pain stimuli when the sham device was activated (ON) but not when the sham device was deactivated (OFF). The control group also got to see a video, but in this video there was no relation between the pain scores of the model and de activation/deactivation of the sham device. The results show that observational learning did not lead to placebo analgesia (F(4.392,92.228) = .557, p = .710). Furthermore, pain expectations did not mediate the relation between observational learning and the placebo effect (b = 0.01, 95% CI [-0.04, 0.10]). These findings contradict previous research that did find a placebo effect induced by observational learning and a mediating role of expectations. Future research should focus on the circumstances in which observational learning does induce a placebo effect. When observational learning does induce placebo responses, the mediating factor of pain expectation should be re-evaluated.Show less
