Pain isn't always a pain. Sometimes it can actually feel good.
People experience pleasure during a painful stimulus if the stimulus turns out to be less bad than they were expecting, new research suggests.
"It is not hard to understand that pain can be interpreted as less severe when an individual is aware that it could have been much more painful," said study co-author Siri Leknes, a psychologist at the University of Oslo in Norway, in a statement. "Less expected, however, is the discovery that pain may be experienced as pleasant if something worse has been avoided."
The findings were published in the March issue of the journal Pain.
To see how people perceived pain, Leknes and her colleagues hooked 16 participants up to a device that applied a variable level of painful heat to their arms. At the same time, the researchers measured their brain activity using magnetic resonance imaging (MRI) scans.
In the first setting, participants experienced a series of either a slightly painful stimulus — about as painful as grasping a slightly too hot cup of coffee — or no pain.
In a second setup, the participants experienced a series of either moderate or intense pain. On a screen, the participants could see what type of pain was coming up next in the series.
In the first scenario, the participants rated the moderate pain as unpleasant.
What a relief
But interestingly, participants rated the moderate pain as actually pleasurable in the second setup, when the alternative was the intense pain. During the moderate stimulus in the second setup, participants' brain activity also showed less activation in the pain region of the brain (the brain stem) and more activation in a region in the middle of the frontal lobes that's associated with pain relief and pleasure than during the same stimulus in the first setup.
"The likely explanation is that the subjects were prepared for the worst and thus felt relieved when they realized the pain was not going to be as bad as they had feared," Leknes said in a statement. "In other words, a sense of relief can be powerful enough to turn such an obviously negative experience as pain into a sensation that is comforting or even enjoyable."
The finding could shed light on why some people experience the burn of hot chili peppers or painful sex as pleasurable.
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Tia is the managing editor and was previously a senior writer for Live Science. Her work has appeared in Scientific American, Wired.com and other outlets. She holds a master's degree in bioengineering from the University of Washington, a graduate certificate in science writing from UC Santa Cruz and a bachelor's degree in mechanical engineering from the University of Texas at Austin. Tia was part of a team at the Milwaukee Journal Sentinel that published the Empty Cradles series on preterm births, which won multiple awards, including the 2012 Casey Medal for Meritorious Journalism.