Scientists have discovered hundreds of genes that appear to play a role in determining pain sensitivity. Researchers say slight variations in one pain gene in particular seem to affect how intensely pain is felt.
Under normal circumstances, scientists say pain serves an important biological function; a sharp poke with a needle or knifepoint, or slight burn, causes most people to recoil, protecting them from further harm.
Then there is another type of pain, according to Clifford Woolf a neurobiologist at Children's Hospital in Boston, Massachusetts.
"The other kind of pain is when the fire alarm system is on all the time, and these would be patients who have chronic persistent pain," Woolf explained. "And that is a situation where pain has become a disease in its own right. It's no longer warning of damage; the fire alarm is on all the time and there's no fire."
Scientists say studies of twins show that the degree to which an individual feels pain is largely inherited.
In an effort to identify genes involved in pain, an international team of researchers led by Woolf identified some 600 potential genes in fruit flies which are similar in humans.
Scientists focused on one gene in particular called "Alpha 2 Delta 3."
In a study of 189 healthy volunteers, researchers found reduced sensitivity to heat among participants who had slight alphabet variations to the DNA code within or close to the location of the Alpha 2 Delta 3 gene.
Researchers also found in another study that back pain patients who had the rarer genetic variants were less likely to experience persisting pain after surgery.
By learning the genetic underpinnings of pain, Woolf says it will someday be possible to develop medications to treat a variety of pain syndromes.
"There's pain associated with damage to the nervous system. Pain associated with the inflammatory diseases," neurobiologist Woolf noted. "There's post-operative pain. And each of them operates in slightly different ways, and so there will be different targets and different analgesics required for these different kinds of pain."
Researchers say it may one day be possible to develop genetic risk profiles to determine who is at greatest risk of chronic pain following surgery. Such information could be useful in helping patients decide whether to go forward with an operation.
An article describing the pain genes is published in the journal Cell.