Conditioned Pain Modulation in Children: The Effects of Painful and Nonpainful Conditioning Stimuli
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Date
2016-01-01
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Department
Psychology
Program
Psychology
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This item may be protected under Title 17 of the U.S. Copyright Law. It is made available by UMBC for non-commercial research and education. For permission to publish or reproduce, please see http://aok.lib.umbc.edu/specoll/repro.php or contact Special Collections at speccoll(at)umbc.edu
Distribution Rights granted to UMBC by the author.
Distribution Rights granted to UMBC by the author.
Abstract
Objective: To experimentally test endogenous pain modulation in children in a laboratory setting via a conditioned pain modulation paradigm. Introduction: Conditioned pain modulation (CPM), a psychophysical measure in which one pain stimulus (conditioning stimulus) is used to inhibit another pain stimulus (test stimulus), is an important indicator of endogenous pain inhibition in adults. The CPM paradigm has interesting clinical relevance in adults, but is understudied in children. There is some preliminary evidence that CPM effects are present in healthy children, and that CPM effects are more robust in older children. However, it is still not fully known if CPM reliably occurs in children or whether CPM responses vary based on child age, and no published study of CPM effects in children has included a nonpainful conditioning stimulus to control for the effects of distraction and other nonspecific effects. Thus, the current study utilized a mixed experimental design, with experimental condition (baseline, painful conditioning stimulus, and nonpainful conditioning stimulus) as the within-subjects factor, child age as the between-subjects factor, and test stimulus (pressure pain threshold) as the dependent variable. It was predicted that children would display a "CPM effect;" i.e., pressure pain thresholds would be inhibited relative to baseline during the painful conditioning stimulus trial. It was also predicted that older children would display a more robust CPM effect. Method: Participants were 54 healthy school-aged children, age range 6-12 years, recruited from the local community. Participants were exposed to multiple pressure pain threshold tests, in which pressure was applied to their right hand until the stimulus first began to feel painful. After a baseline assessment, participants underwent two cold pressor trials in which they placed their left hand in a water bath at either 12°C (painful conditioning stimulus) or 22°C (nonpainful conditioning stimulus), and pressure pain threshold was assessed during each cold pressor exposure. Results: Data were analyzed using a repeated measures ANOVA and multilevel mixed regression modeling, with experimental condition as a within-subjects factor for both analyses, child age (measured as a continuous variable) and duration of cold water exposure included as continuous predictors in the mixed regression models, and pressure pain threshold scores as the dependent variable. Results indicated that participants displayed a significant "CPM effect," such that their pressure pain thresholds were significantly higher during the painful conditioning stimulus trial when compared to baseline and the nonpainful conditioning stimulus trial. There were no significant differences in magnitude of the CPM effect based on age. Conclusions: The current study replicates and expands on findings regarding CPM in children. It utilized a refined methodology for testing CPM in children, and provides information about the development of descending pain inhibitory pathways. Future studies could utilize pediatric CPM paradigms to examine predictors of chronic pain in children or to test their responses to pain intervention.