 In addition, some studies have indicated that cigarette smoking was strikingly present in patients and is statistically linked to RSD.This may be involved in its pathology by enhancing sympathetic activity, vasoconstriction, or by some other unknown neurotransmitter-related mechanism.This hypothesis was based on a retrospective analysis of 53 patients with RSD, which showed that 68% of patients and only 37% of controls were smokers.