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The following is a summary of “Expectation of analgesia increases the inhibitory response of conditioned pain modulation in healthy participants who at baseline have a non-inhibitory profile,” published in the November 2024 issue of Pain by Nascimento et al. 

Researchers conducted a retrospective study to examine the healthy participants and effect of analgesia expectation on conditioned pain modulation (CPM) in categorized as inhibitors and non-inhibitors.  

They assessed a parallel CPM protocol on 21 women and 22 men over 2 sessions: baseline and expectation of analgesia induced by an audiovisual suggestion, 2 test stimuli (TS) were used: mechanically controlled palpation and the pressure pain threshold, applied to the anterior temporalis and thenar eminence. The conditioning stimulus (CS) involved cold water immersion of the non-dominant forearm. The order of TS and regions was randomized, and the protocol was performed 3 times with 1-minute intervals between sequences. After a 20-minute rest, the assessment was repeated in 2 blocks. The Standard error of measurement (SEM) was calculated to categorize inhibitors (inhibitory responses) and non-inhibitors (non-inhibitors and facilitatory responses). Data were analyzed using Cochran’s Q, ANOVA, and ANCOVA (P < 0.05).  

The results showed a significant decrease in non-inhibitors during the expectation of analgesia session (32.6%-44.2%) compared to baseline (51.2%-72.1%). Non-inhibitors had lower inhibitory CPM magnitude than inhibitors only in baseline block 1. The expectation of analgesia increased inhibitory CPM magnitude solely in non-inhibitors.  

Investigators concluded the expectation of analgesia in healthy individuals could enhance the inhibitory response of CPM who initially exhibit a non-inhibitory profile, surpassing measurement error.   

Source: onlinelibrary.wiley.com/doi/abs/10.1002/ejp.4747