Decades after McGill University psychologist Ronald Melzack's pioneer collection of 78 "pain words" became the McGill Pain Questionnaire -burning, stabbing, flickering, pulsing, radiating, piercing, squeezing, nauseating, tearing, to name a few -scientists still puzzle over why some people go on to develop chronic pain while others are spared.
About 6,000 leading experts have gathered in Montreal this week for the 13th World Congress on Pain at the Palais des congres - dubbed the "Olympics of Pain" by Jeffrey Mogil, scientific committee chair of the conference. Yesterday, participants said the mystery of chronic pain continues to deepen.
One in five people suffer pain that lingers beyond three months, and up to 50 per cent will endure chronic pain in their lifetime, making the condition a throbbing public health issue.
Researchers are investigating how environmental and genetic factors, gender and age differences and lifestyle factors are linked to pain. They are also making inroads on regenerating nerves and preventing nerve damage.
"A lot of this conference is soul searching about what's going on in order to make it better," said Mogil, professor of pain studies at McGill. "Ultimately, I think it comes down to the fact that pain is deeply complex -complex in ways that no one realizes."
A disadvantage of the research, Mogil added, is that "pain is fundamentally subjective and there's no objective way of measuring it."
It is often also seen as a symptom rather than as a disease itself. Mogil contends that compared to other fields, pain research is grossly underfunded, even though it should be considered the No. 1 health problem. "There are more pain sufferers in the world than cancer, diabetes and heart patients combined," he said.
It is widely believed that pain affects men and women differently. Women experience chronic pain longer, more intensely and more often than men.
"The differences are dramatic," Mogil said of neural networks that moderate pain.
Human drug trials are under way to determine what works for men vs. women. That means eventual targeted therapies, Mogil said: "There will be blue pills and pink pills."
The next 20 years will see a revolution in pain management, according to Gerald Gebhart, president of the International Association for the Study of Pain. "We're just at the beginning of understanding the genetics of pain," he said.
New discoveries are coming, but not as fast as some would like, said Gebhart, director of the Center for Pain Research at the University
of Pittsburgh School of Medicine.
When Melzack and colleague Patrick David Wall proposed the gate control theory of pain in 1965 (which suggested that pain is gated, or filtered by neural gates in the spinal cord, and is affected by past experiences), it ushered in a new era of pain research.
Now the pharmaceutical industry is aggressively seeking new treatments, Gebhart said.
"But what we've learned over the years is that pain is more complicated," he said. "It's not a simple problem of finding a better drug, but of finding a better strategy based on the understanding of the causes and mechanism of pain."
Also, drugs are often accompanied by unwanted side effects, he added. "The more we understand, the harder it is to go forward."
Pain is a useful tool that teaches survival and protection, said Eija Anneli Kalso, professor of pain research and management at the University of Helsinki. It's a different story when pain persists long after the initial injury heals, Kalso said (adding that magnetic resonance images of people with prolonged pain shows changes to the brain, including shrinking grey matter, although that's reversible with effective pain management).
All the more reason to focus on prevention and early treatment, said Universite de Montreal clinical researcher Manon Choiniere. Patients often waste months or years going from doctor to doctor while their pain worsens and becomes more difficult to treat, she said.
"And finally they are referred to a pain clinic, but there's a wait of up to two years to get in."