Pain and neuroendocrine responses to experimentally-induced noxious stimulation: A randomized, controlled trial of hypnotic analgesia

The efficacy of hypnotic analgesia has been demonstrated in previous controlled trials involving clinical pain problems and induced pain in laboratory settings. Individuals who screen high for hypnotizability often report marked reductions in pain ratings, particularly the affective dimension, following administration of hypnotic suggestions. However, the role of hypnotic analgesia in shaping neuroendocrine responses has, to date, received minimal attention. This study was a randomized, controlled trial that sought to compare differences in pain ratings and adrenocortical responses to cold pressor induced pain in individuals receiving either hypnotic suggestion (treatment) or no intervention (control). Potential participants were screened according to standardized hypnotizability scales. A total of 24 healthy and highly hypnotizable individuals completed the study (12 treatment, 12 control). Study participants each completed two pain induction sessions and provided saliva samples for cortisol assay across each session. Approximately two weeks separated pain testing sessions; during this time the treatment group participated in therapist- and self-facilitated hypnosis while the control group was not offered or instructed to do anything. Results revealed significant group effects for pain intensity (F(2,21)=3.58,p=.04) and pain unpleasantness (F(2,21)=4.01,p=.03) ratings, such that the treatment group reported significantly lower ratings compared to the control group following intervention. Total cortisol production significantly decreased for both groups across the two sessions (F(1,22)=5.36,p=.03). However, CPT-induced cortisol reactivity was significantly less for the treatment group compared to the control group post-intervention (F(1,22)=8.02,p = .01). This study provides further evidence supporting hypnotic analgesia and, to our knowledge, is the first to demonstrate a relation between hypnosis and adrenocortical reactivity. The ability of hypnosis to modify HPA axis responses following acute noxious stimulation is encouraging and underscores the potential of hypnotic interventions for maintaining and/or restoring homeostasis following a stressful event. Further investigation of the hypnotic analgesia-neuroendocrine relation appears warranted.