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Effect of stressful imagery on thermal pain ratings of patients with fibromyalgia: What mediates this relationship?
Renata M. Okonkwo, MA1, Laurence A. Bradley, PhD1, Adriana Sotolongo, BA1, Ronda Cannon, BS1, and Roger B. Fillingim, PhD2. (1) Division of Clinical Immunology and Rheumatology, University of Alabama at Birmingham, 1825 University Blvd, 178E Shelby Research Bldg., Birmingham, AL 35294, (2) Department of Community Dentistry and Behavioral Science, University of Florida, P.O. Box 103628, Gainesville, FL 32610-3628
Aims: Identify (a) effects of personally-relevant, stressful imagery on thermal pain ratings of patients with FM and healthy controls (HCs); and (b) psychosocial variables that mediate group differences in these ratings. Methods: 22 female patients with FM and 30 female HCs completed Center for Epidemiologic Studies-Depression (CES-D) scale and Coping Strategies Questionnaire (CSQ) before first visit. Visit 1: Participants performed two magnitude estimate (ME) tasks in which they used 100 cm, mechanical VAS (M-VAS) to rate intensity (INT) and unpleasantness (UNP) of 4 stimuli (45°C - 51°C) applied to left forearm (Medoc TS-2001). Prior to each task, investigator guided participants through a 4-minute, personally-relevant, stressful or control imagery induction procedure. Visit 2: Participants performed 4 temporal summation (TS) tasks (2 series of high and 2 series of low intensity thermal stimuli) and produced M-VAS ratings of INT and UNP after each task. Each task was preceded by a 4-minute, personally-relevant stressful or control imagery induction procedure. Analyses: CES-D and CSQ Catastrophizing and Pain Control subscale scores entered in one-way ANOVAs. Change scores (Stress - Neutral Imagery) for pain ratings on the ME and TS tasks entered in repeated-measures ANOVAs. Regression analyses (1) performed to determine whether CES-D or CSQ scores mediate group differences in stressor-evoked changes in pain ratings. Results: Patients, compared to HCs, produced (a) higher scores on CES-D and CSQ subscales (p's=.001); and (b) greater stressor-evoked increases in pain UNP ratings on ME and TS tasks (p's=.043-.048). Perceived ability to control pain fully mediated group difference in stressor-evoked changes in pain UNP on TS task. Conclusions: Stressors enhance patients' ratings of tonic pain UNP. Effect is mediated by perceived ability to control pain. Must determine if treatment-related increases in perceived ability to control pain decrease clinical pain or suffering. Reference 1: Baron & Kenny, J Person Soc Psychol, 1986