Researchers at Keele University last year published a study that showed swearing reduces pain. Okay, so the pain they were talking about was acute pain brought by submerging hands in ice cold water... not exactly RSD... but still interesting.
In the study volunteer human guinea pigs were told to either repeat a neutral word or a profanity of their choice while their hands were submerged in ice cold water. When swearing, the 67 student volunteers reported less pain and on average endured about 40 seconds longer.
Scientists speculate that this reaction is because swearing triggers an emotional reaction in the brain, thereby triggering the amygdala, aka the part of the brain responsible for triggering the fight/flight mechanism and stress response.