Conditioned Pain Modulation (CPM) Paradigms: Reliability and Relationship With Individual Characteristics

Abstract

Purpose: Conditioned Pain Modulation (CPM) is a useful tool for testing the functionality of endogenous pain modulation. However, inconsistent results have been obtained in clinical populations, possibly due to the wide variety of CPM protocols used and the influence of demographic and psychological charac teristics of the individuals assessed. Methods: We tested the sensitivity and reliability of four commonly used CPM paradigms in a sample of 58 healthy participants. We also checked how these measures were related to Temporal Summation of Second Pain (TSSP), sociodemographic (age and sex) and psychological variables (anxiety and stress). Results: CPM results were influenced by the test stimulus used, with tests using pain pressure threshold (PPT) obtaining a greater number of responders (over 65%) and being the most sensitive (higher size effect: Cohen’s d > 0.5). However, all measures showed excellent intrasession reliability, with strong agreement between the CPM magnitudes. CPM indices were not correlated with TSSP, age or sex, and the psychological scales did not differentiate CPM responders and non-responders. Conclusions: Although the CPM indices showed good reliability, construction of a large database with standardized values for healthy individuals seems necessary for the use of CPM in clinical settings.