Classical conditioning without verbal suggestions elicits placebo analgesia and nocebo hyperalgesia
Classical conditioning without verbal suggestions elicits placebo analgesia and nocebo hyperalgesia
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DOI：
10.1371/journal.pone.0181856
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发表时间：
2017-07-27
期刊：
影响因子：
3.7
通讯作者：
Colloca, Luana
中科院分区：
文献类型：
--
作者：
Babel, Przemyslaw;Bajcar, Elzbieta A.;Colloca, Luana
本研究旨在探讨安慰剂镇痛和反安慰剂痛觉过敏中经典条件反射、期望和恐惧之间的关系。共有42名健康志愿者被随机分配到三组：安慰剂，nocebo和控制。他们接受了96次电刺激，之前是橙子或蓝色的灯光。在安慰剂组和反安慰剂组中进行了一个隐藏的条件反射程序，参与者没有被告知彩色灯光的含义。一种颜色的光与中等强度的疼痛刺激（对照刺激）配对，另一种颜色的光与非疼痛刺激（安慰剂组）或高强度的疼痛刺激（反安慰剂组）配对。在对照组中，这两种颜色的光，其次是控制刺激的中等强度，没有任何条件反射程序。参与者对疼痛强度、疼痛强度预期和恐惧进行评分。在测试阶段，当两种颜色的灯光之后是相同的中度疼痛刺激时，我们发现安慰剂组有显著的镇痛作用，反安慰剂组有显著的痛觉过敏作用。无论是预期或恐惧评级预测安慰剂镇痛或nocebo痛觉过敏。看起来，一个隐藏的条件反射程序，没有任何明确的口头建议，消除安慰剂和反安慰剂效应，然而，我们没有发现任何证据表明这些效应是由预期或恐惧预测的。这些结果表明，经典条件反射可能是安慰剂和反安慰剂效应的不同机制。
The aim of this study was to examine the relationships among classical conditioning, expectancy, and fear in placebo analgesia and nocebo hyperalgesia. A total of 42 healthy volunteers were randomly assigned to three groups: placebo, nocebo, and control. They received 96 electrical stimuli, preceded by either orange or blue lights. A hidden conditioning procedure, in which participants were not informed about the meaning of coloured lights, was performed in the placebo and nocebo groups. Light of one colour was paired with pain stimuli of moderate intensity (control stimuli), and light of the other colour was paired with either non-painful stimuli (in the placebo group) or painful stimuli of high intensity (in the nocebo group). In the control group, both colour lights were followed by control stimuli of moderate intensity without any conditioning procedure. Participants rated pain intensity, expectancy of pain intensity, and fear. In the testing phase, when both of the coloured lights were followed by identical moderate pain stimuli, we found a significant analgesic effect in the placebo group, and a significant hyperalgesic effect in the nocebo group. Neither expectancy nor fear ratings predicted placebo analgesia or nocebo hyperalgesia. It appears that a hidden conditioning procedure, without any explicit verbal suggestions, elicits placebo and nocebo effects, however we found no evidence that these effects are predicted by either expectancy or fear. These results suggest that classical conditioning may be a distinct mechanism for placebo and nocebo effects.