Conditioned pain modulation (CPM) is a psychophysical experimental measure of endogenous pain inhibition in humans. Within this paradigm, one noxious stimulus, the conditioning stimulus (CS), reduces the pain perception from another heterotopic noxious stimulus, the test stimulus (TS). Cognitive processes are known to influence pain perception and might impact the underlying mechanisms of CPM. This systematic review and meta-analysis synthesizes the existing scientific literature addressing the influence of cognitive factors, namely, expectations and attention on CPM. Four electronic databases were searched to identify relevant literature. Risk of bias and quality of evidence were assessed according to two modified Newcastle-Ottawa Scales and the GRADE approach, respectively. Twenty-four articles were included. Qualitative analysis showed more efficient CPM when pain relief is expected, and an association between intrinsic attention to pain and reduced CPM. Although the evidence is not unanimous, meta-analyses showed that CPM is more efficient when attention is directed towards the CS versus the TS, and is not influenced by distraction. In conclusion, while CPM seems robust to attentional distraction, expectations and attentional focus appear to influence CPM. However, the evidence is limited and conflicting and warrants further study in order to prevent cognitive confounding and enhance mechanistic understanding.

中文翻译：

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期望和关注对条件性疼痛调节的影响：系统评价和荟萃分析


条件性疼痛调节 （CPM） 是人类内源性疼痛抑制的心理物理实验测量。在这种范式中，一种有害刺激，即条件刺激 （CS），减少了来自另一种异位有害刺激，即测试刺激 （TS） 的疼痛感知。已知认知过程会影响疼痛感知，并可能影响 CPM 的潜在机制。本系统评价和荟萃分析综合了现有的科学文献，涉及认知因素的影响，即期望和关注对 CPM 的影响。检索 4 个电子数据库以确定相关文献。分别根据两种改良的纽卡斯尔-渥太华量表和 GRADE 方法评估偏倚风险和证据质量。包括 24 篇文章。定性分析显示，当预期疼痛缓解时，CPM 更有效，并且对疼痛的内在关注与降低的 CPM 之间存在关联。尽管证据并不一致，但荟萃分析表明，当注意力集中在 CS 上时，CPM 比 TS 更有效，并且不受分心的影响。总之，虽然 CPM 似乎对注意力分散很稳健，但期望和注意力集中似乎会影响 CPM。然而，证据有限且相互矛盾，值得进一步研究，以防止认知混淆并增强机械理解。