Associations between psychological variables and pain in experimental pain models. A systematic review

Background The association between pain and psychological characteristics has been widely debated. Thus, it remains unclear whether an individual's psychological profile influences a particular pain experience, or if previous pain experience contributes to a certain psychological profile. Translational studies performed in healthy volunteers may provide knowledge concerning psychological factors in healthy individuals as well as basic pain physiology. The aim of this review was to investigate whether psychological vulnerability or specific psychological variables in healthy volunteers are predictive of the level of pain following experimental pain models. Methods A systematic search on the databases, PubMed, Embase, Cochcrane library, and Clinicaltrials.gov was performed during September 2014. All trials investigating the association between psychological variables and experimental pain in healthy volunteers were considered for inclusion. Results Twenty-nine trials met the inclusion criteria, with a total of 2637 healthy volunteers. The included trials investigated a total of 45 different psychological tests and 27 different types of pain models. The retrieved trials did not present a sufficiently homogenous group to perform meta-analysis. The collected results were diverse. A total of 16 trials suggested that psychological factors may predict the level of pain, seven studies found divergent results, and six studies found no significant association between psychological variables and experimental pain. Conclusion Psychological factors may have predictive value when investigating experimental pain. However, due to substantial heterogeneity and methodological shortcomings of the published literature, firm conclusions are not possible.