Pilot study of inflammatory responses following a negative imaginal focus in persons with chronic pain: analysis by sex/gender.

BACKGROUND

Recent evidence suggests that differential stress and immune responses may play a role in the sex/gender disparity for pain. Pain pathology and psychological stress are both associated with elevated levels of proinflammatory cytokines.

OBJECTIVE

This pilot study tested a negative imaginal focus to assess whether it would elicit a proinflammatory cytokine response and whether responses would vary by sex/gender.

METHODS

Adults with chronic musculoskeletal pain were recruited from an outpatient, multidisciplinary pain clinic in Portland, Oregon, between 2007 and 2008. All participants underwent a psychologist-guided 10-minute focus on the negative aspects of their pain condition and the imagined worsening of their pain; no control group was used. Serum collected at baseline and postfocus (1, 2, and 2.5 hours) was assayed for interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha). Cortisol was assayed at each time point and at 15 minutes postfocus.

RESULTS

Thirty-six outpatients (aged 26-62 years; 23 women, 13 men) participated in the study. Compared with men, women displayed greater negative emotional expression during the experiment, and this in turn mediated their IL-6 inflammatory responses. Relative to men, the IL-6 response trajectory was delayed for women. The IL-6 and TNF-a findings suggest women's maximal cytokine responses were not captured by the final time point.

CONCLUSIONS

This pilot study provides preliminary evidence that women with chronic pain may experience increased and delayed inflammatory responses following negative emotional expression induced by thinking negatively about their pain condition. The findings have implications for pain catastrophizing research. This early-phase research suggests that the timing and duration of the cytokine response are critical factors to consider in future pain research.