Recent NIDA-funded research suggests a physiological difference as the explanation for African-Americans' reported low tolerance for pain. Dr. Susan Girdler and colleagues at the University of North Carolina at Chapel Hill monitored the stress responses of 51 African-American and 55 other participants, mostly Caucasians, while subjecting them to three different types of painful stimuli—ischemic, heat, and cold. The results suggest that blood pressure rises and physiological stress responses helped to offset pain sensations among the non-African-Americans, but not the African-Americans. For example, among the non-African-Americans, greater stress-induced increases in blood pressure and release of norepinephrine correlated with more tolerance to subsequent pain. No such relationship was seen among African-Americans, who exhibited less marked blood pressure rises and relatively low levels of the stress hormones.
Psychosomatic Medicine 67(6):948-956, 2005.