Submitted by admin on Tue, 2005-10-18 08:00. ::
"There are dramatic differences in the way we cope and react," says Dr. Angela Mailis-Gagnon, director of the comprehensive pain program at Toronto Western Hospital. "That determines how much pain we feel."
In her book Beyond Pain -- Making the Mind Body Connection, Mailis-Gagnon says there is growing agreement chronic pain is multidimensional. In order to understand it, those treating it must account for its psychological, social and biological dimensions.
"You can't split the body from the mind," she says. "You can't take the emotional impact of a particular injury away. What makes a difference is not what's wrong with us but how we view it (and) the circumstances under which it happens."
"On average almost 50% of the variability between people is due to genes," says Jeff Mogil, a neuroscientist and professor of pain studies at McGill University.
"Similarly there are any number of infections or injuries that can lead to chronic neuropathic pain. Some people that get in car accidents develop causalgia," he says.
"A lot of people are starting to think that people who are developing chronic pain is because they have some genetic susceptibility," Mogil says. "If you have the predisposition, but you never have the injury, you won't have the chronic pain."
"Who's going to get in a car accident and who isn't? And in it, are you going to injure your nerve or not? It's a lottery and the genetics are a lottery too," says Mogil, a Canadian Research Chair in the genetics of pain.
Mailis-Gagnon believes just 40% of the variability in pain tolerance, threshold and reactions comes from genes, while a person's environment accounts for 60%.
"What I have said all along is that input -- physical or emotional -- may end up altering the way the nervous system codes pain and the way a person reacts."
Dr. Karen J. Berkley, a professor of neuroscience at Florida State University who's studied neural mechanisms of pain for 35 years, says from the day a person is born their nervous system is being trained to decide what's painful and what's not, all to protect them and spur them to take action when needed.
"Between 45%-50% did not hurt," Berkley says. "They started to hurt 2-3 hours later." Everyone immediately thinks shock suppressed the pain, that it was more important after a crash to get the hell out of there.
"It would be stupid for the nervous system to make you curl up into a ball and stay there," she says. "The nervous system decides what is important for you to do."
"If you have a number of painful experiences as a kid in a hospital ... you're marked for life," Mailis-Gagnon says. "You will grow much more sensitive to pain."
Research indicates the same seems to hold true for little boys who are circumcised. They had far stronger negative reactions to their immunizations.
It was long thought that newborns didn't feel pain and there was a time when surgeries would be performed on them without any anesthetic. Studies have since shown that even the common practice of pricking the heels of new babies leads to increased sensitivity to pain because they were exposed to it early on.
Like any relationship involving men and women, sex and chronic pain is complicated. There is a higher prevalence of painful diseases in women. Fibromyalgia, for instance, affects women seven times more often than men.
There's no doubt sex hormones play a role and act on the nervous system, but Berkley says the field is just beginning to acknowledge and trying to understand that.
"Does testosterone make you hurt more? Does it protect you? Does estrogen? It's not a simple answer. You can get yes to both of those and you can also get no," she says. "It may not be so much of how much you have of a hormone, but the combination and how they're changing. Are they increasing or decreasing? Sometimes it's a change that triggers an effect."
Mailis-Gagnon says sex hormones play an active role in modulating the balance of neurotransmitters, which is significant because neurotransmitter abnormalities are found in some chronic pain conditions.
Women also report more depression and psychological distress, each of which are known to enhance pain, which may also explain some of the sex differences.
There is evidence that pain can also be learned, as is the case among children who grow up around parents or close family members who experience pain.
Dr. David Corey, president of the Health Recovery Clinic, an interdisciplinary pain program in Toronto, says he always asks patients with chronic pain if they had a family member go through a similar type of problem.
Dr. Patrick McGrath, a psychologist at IWK Health Centre in Halifax and the Canada Research Chair in pediatric pain based at Dalhousie University, says it's true that modeling and reinforcement play an important role. There's no doubt if dad has a bad back and uses it to avoid work, the child is going to learn something very different than if dad does all he can to manage his pain and doesn't complain. But McGrath says physiology and psychology can't be separated.
"Family factors are important, but it's really too easy to blame the family. Psychologists are often too ready to blame mothers for anything," he says. "It's very unlikely that (experience) would cause pain without the physiological underpinning. If your mother has migraines, chances are you're going to have migraines."
Not only can this extend the duration of pain, it can increase the intensity. Research in Germany looking at the brain activity of patients with back pain found that when a doting spouse was in the room, the patient felt much more pain. This was measured by functional (MRI) imaging, which saw the pain lessen when the spouse left the room.
"We now think reassurance may make kids' pain worse,"McGrath says. "We're not sure. It could be that it draws attention to the pain (and) encourages the kids to express pain, so he has more pain."
Childbirth is a similar story. Originally from Greece, Mailis-Gagnon says "having a kid (in Greece) is considered a natural thing, like the wind." Epidurals aren't the norm.
In East Africa a surgical procedure called trepanation is done without anesthetic or painkillers, and sees the patients' head muscles cut to uncover the skull. While the doctor works, the patient is awake and holding the pan to catch dripping blood.
Some people say there is always a physical injury at the root of chronic pain. But Mailis-Gagnon says there are multiple interpretations, given that in most patients, the initial physical stimuli is not that big.
Often, it's the memory of pain that remains long after the injury has faded. That's particularly true if it was frightening or emotionally arousing.
Most people assume because they have pain, something is wrong with their body. But Corey says many types of pain, including headaches and charley horses, do no harm.
The link between pain and depression is clear. What isn't, however, is which comes first. That's because depression is more prevalent in people with chronic pain, but those with depression also have more pain.
Complicating the understanding of chronic pain even further are a minority of people in which pain arises without any physical stimuli. Instead it's brought on by thought or emotion.
Although it's an extreme example, Mailis-Gagnon refers to parts of Africa where women come in from working in the fields, deliver their children and then go back to work. Meanwhile her husband is left suffering in bed, accepting congratulations from other members of the tribe.
There, the filter that's been at work since the day we were born, deciding what's important to pay attention to and what can be ignored, seems to be affected in chronic pain patients.
In most people, the brain is exposed to a barrage of stimuli -- light, sound, smell and internal stimuli -- but it only pays attention to those that matter. That's what allows us to go through life.
But in pain patients, this filter is messed up. Their nervous systems become oversensitized. Things that wouldn't normally be painful develop a chronic pain reaction.
"There is evidence now from MRI studies that patients with chronic pain, when given a stimulus that has one reaction in normal (patients), it has a different response in those with chronic pain," Corey says.
Reducing that hyperactivity involves untraining the nervous system and can involve learning relaxation techniques, behavioural changes and guided imagery.
The bottom line: When pain becomes longstanding and interferes with quality of life, there's always more than just a simple injury or disease to a body part.
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