Stubbed your toe? Burned your hand on a hot pot? Go ahead and curse. It might make you feel better.
It also increased heart rate and decreased perceived pain -- signs of a "fight-or-flight" response that may help mitigate actual pain, according to Richard Stephens of Keele University in Staffordshire, U.K.
"If people experience the emotion of fear to a significant degree … their pain tolerance increases," Stephens said. "There seems to be something similar here. Swearing is emotional language. If it's not fear, it might be aggression."
Dr. Gail Saltz, professor of psychiatry at New York Presbyterian Hospital and a psychoanalyst with the New York Psychoanalytic Institute, said that a fight-or-flight response absorbs mental capacity so you can't think about your pain, and increases certain nervous system functions while slowing down others -- such as gut function -- to maximize chances of survival.
She said pain tolerance also has a lot to do with coping mechanisms, distraction being a key example.
"If you're screaming obscenities, you're not thinking about your pain," she said. "The distraction compartmentalizes the other experience."
Researchers say that swearing has long been a common response to pain.
"Many a woman in the delivery room has already figured that out," Dr. Saltz said.
But whether swearing alters a patient's experience of pain hasn't been formally studied.
So Stephens and colleagues conducted a study of 67 undergraduates from Keele University who were asked to submerge one of their hands in freezing cold water.
One group was told to utter a curse word of their choice during the immersion, while a control group repeated an innocuous word that would be used "to describe a table."
The researchers looked at how long both groups left their hands in the water as a measure of pain tolerance. They also measured pain perception and heart rate immediately following the submersion.
They found that swearing significantly increased pain tolerance and heart rate, and decreased perceived pain, compared with not swearing.
"If they swore, they held their hands in cold water for longer," Stephens said.
The effect on improved pain tolerance was similar in both males and females, but it led to a greater reduction in perceived pain and a greater increase in heart rate among females.
However, the researchers said that the "most intriguing" finding was that the pain-killing effect of swearing didn't work for males with a tendency to catastrophize, or think the worst in terms of their own outcomes.
Though the researchers didn't have an explanation for these findings, they noted in the study that it may occur because the "negative emotions induced by swearing spill over into catastrophic thinking in those more predisposed to such thinking."
If it's not just the fight-or-flight mechanism at work in terms of pain tolerance, it could also be that swearing induces a negative emotion that may still be characterized as an immediate alarm reaction to a threat.
It may also induce aggression or downplay "feebleness in favor of a more pain-tolerant machismo," the researchers said.
"There's something about the release of feeling that seems to have a positive effect on pain tolerance," said Dr. Mark Smaller, a psychoanalyst in private practice in Chicago. "Swearing would be an expression of intense release of feeling."
Smaller said the findings seem consistent with an idea in psychoanalysis that increased expression "can diffuse the intensity of emotional pain."