The transferable placebo effect from pain to emotion: changes in behavior and EEG activity.

Past studies indicate that the placebo expectation established by analgesic treatment significantly relieves pain perception, while ataractic treatment significantly alleviates unpleasant arousal evoked by negative picture processing. But it is unclear whether the placebo effect can be transferred from one domain to the other, namely from pain to emotion. In this study we led participants to believe in the analgesic effect of magnetic treatment equipment (the placebo) by secretly reducing the intensity of pain stimulus. Then, we examined if this placebo could significantly alter participants' negative affect evoked by watching unpleasant pictures. Our results indicated a significant transferable placebo effect that alleviated negative feelings. EEG recordings showed the transferable placebo treatment induced decreased P2 amplitude and increased N2 amplitude, with source location near the posterior cingulate.