The influence of attention and expectations on the efficacy of conditioned pain modulation: An experimental study.

Introduction: Despite the considerable amount of research performed on conditioned pain modulation (CPM), there are still uncertainties concerning the influence of cognitive mechanisms on CPM efficacy.1 This study aimed to investigate whether the CPM effect is influenced by attention and expectations in healthy adults. Methods: Seventy-two healthy pain-free adults participated in this cross-sectional study undergoing CPM evaluation (i.e. pain pressure threshold (PPT) assessment (= test stimulus (TS)) in response to hot water hand submersion (=conditioning stimulus (CS)) during three experimental protocols administered in randomized order, i.e. (1) a sequential 'neutral' protocol, (2) a 'focus' protocol during which attention was focused on the CS, and (3) a 'distraction' protocol during which attention was directed away from the CS using a distraction task. Participants their pain expectations were recorded before each of the three protocols. Results: Compared to the other protocols, focusing the attention on the CS resulted in smaller CPM magnitudes (p < 0.001), and the distraction protocol resulted in lower NRS ratings for the CS (p < 0.001). A priori expectations accounted for 6.6% of the CPM effect of the neutral protocol (p = 0.035), with expectations of analgesia predicting more efficient CPM. Discussion: It is recommended to rate CS-related pain intensity after CS completion rather than during CS to prevent a reduction of the inhibitory effects by the CPM paradigm. Participants' a priori expectations should be registered as these can influence the induced CPM magnitude. Process evaluation: Building the appropriate statistical models, which took into account confounding factors as well as randomization sequence, was challenging. [ABSTRACT FROM AUTHOR]