Biological mechanisms related to the effectiveness of guided imagery for chronic pain.

Specific aims of this pilot study were to (a) determine the effect of a guided imagery (GI) intervention over an 8-week period on pain and pain disability in a sample of persons with chronic noncancer pain (CNCP) and (b) analyze the mediating effects of neuroendocrine and neuroimmune functioning on the effectiveness of GI on outcome variables. A simple interrupted time-series design (12-week period) was used. GI was introduced at Week 4 and used daily by 25 participants for the remaining 8 weeks. Measures of pain and pain disability were obtained at the beginning of the study period and at six repeated 2-week intervals. Measures of hypothalamic-pituitary-adrenal (HPA) axis activation (plasma cortisol), immune-mediated analgesia (lymphocyte subset counts and proliferation), and immune-mediated hyperalgesia (interleukin-1β) were obtained at the beginning of the study and at Week 11. Usual pain levels were lower after the introduction of GI at Week 4 (Wilks' λ = 52.31; df = 2, 22; p = .000). Pain disability levels were lower after the introduction of GI at Week 4 (Wilks' λ = 5.98; df = 6, 18; p = .001). Correlation coefficients between change scores of dependent variables and mediating variables were not significant. GI was effective in reducing pain intensity and pain disability over an 8-week period; however, the results did not support the expected effects of decreased HPA axis activation, improved immune-mediated analgesia, and reduced immune-mediated hyperalgesia in mediating these outcomes. These findings may be related to procedural and theoretical issues and limitations related to the study design.