Cold Pressor Pain Sensitivity in Monozygotic Twins Discordant for Chronic Fatigue Syndrome


Philip M. Ullrich, PhD, Department of Rehabilitation Medicine, Box 359740, Harborview Medical Center, 325 Ninth Ave, Seattle, WA 98104, USA. Tel: 206-277-3911; Fax: 206-764-2935; E-mail:


Objective.  Individuals with chronic fatigue syndrome (CFS) experience many pain symptoms. The present study examined whether pain and fatigue ratings and pain threshold and tolerance levels for cold pain differed between twins with CFS and their cotwins without CFS.

Design.  Cotwin control design to assess cold pain sensitivity, pain, and fatigue in monozygotic twins discordant for CFS.

Patients and Setting.  Fifteen monozygotic twin pairs discordant for CFS recruited from the volunteer Chronic Fatigue Twin Registry at the University of Washington.

Results.  Although cold pain threshold and tolerance levels were slightly lower in twins with CFS than their cotwins without CFS, these differences failed to reach statistical significance. Subjective ratings of pain and fatigue at multiple time points during the experimental protocol among twins with CFS were significantly higher than ratings of pain (P = 0.003) and fatigue (P < 0.001) by their cotwins without CFS.

Conclusions.  These results, while preliminary, highlight the perceptual and cognitive components to the pain experience in CFS. Future studies should focus on examining the heritability of pain sensitivity and the underlying mechanisms involved in the perception of pain sensitivity in CFS.